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The central nervous system brain: Central nervous system: Structure, function, and diseases


Central nervous system: Structure, function, and diseases

The central nervous system consists of the brain and spinal cord. It is referred to as “central” because it combines information from the entire body and coordinates activity across the whole organism.

This article gives a brief overview of the central nervous system (CNS). We will look at the types of cells involved, different regions within the brain, spinal circuitry, and how the CNS can be affected by disease and injury.

The CNS consists of the brain and spinal cord.

The brain is protected by the skull (the cranial cavity) and the spinal cord travels from the back of the brain, down the center of the spine, stopping in the lumbar region of the lower back.

The brain and spinal cord are both housed within a protective triple-layered membrane called the meninges.

The central nervous system has been thoroughly studied by anatomists and physiologists, but it still holds many secrets; it controls our thoughts, movements, emotions, and desires. It also controls our breathing, heart rate, the release of some hormones, body temperature, and much more.

The retina, optic nerve, olfactory nerves, and olfactory epithelium are sometimes considered to be part of the CNS alongside the brain and spinal cord. This is because they connect directly with brain tissue without intermediate nerve fibers.

Below is a 3D map of the CMS. Click on it to interact and explore the model.

Now we will look at some of the parts of the CNS in more detail, starting with the brain.

The brain is the most complex organ in the human body; the cerebral cortex (the outermost part of the brain and the largest part by volume) contains an estimated 15–33 billion neurons, each of which is connected to thousands of other neurons.

In total, around 100 billion neurons and 1,000 billion glial (support) cells make up the human brain. Our brain uses around 20 percent of our body’s total energy.

The brain is the central control module of the body and coordinates activity. From physical motion to the secretion of hormones, the creation of memories, and the sensation of emotion.

To carry out these functions, some sections of the brain have dedicated roles. However, many higher functions — reasoning, problem-solving, creativity — involve different areas working together in networks.

The brain is roughly split into four lobes:

Temporal lobe (green): important for processing sensory input and assigning it emotional meaning.

It is also involved in laying down long-term memories. Some aspects of language perception are also housed here.

Occipital lobe (purple): visual processing region of the brain, housing the visual cortex.

Parietal lobe (yellow): the parietal lobe integrates sensory information including touch, spatial awareness, and navigation.

Touch stimulation from the skin is ultimately sent to the parietal lobe. It also plays a part in language processing.

Frontal lobe (pink): positioned at the front of the brain, the frontal lobe contains the majority of dopamine-sensitive neurons and is involved in attention, reward, short-term memory, motivation, and planning.

Brain regions

Next, we will look at some specific brain regions in a little more detail:

Basal ganglia: involved in the control of voluntary motor movements, procedural learning, and decisions about which motor activities to carry out. Diseases that affect this area include Parkinson’s disease and Huntington’s disease.

Cerebellum: mostly involved in precise motor control, but also in language and attention. If the cerebellum is damaged, the primary symptom is disrupted motor control, known as ataxia.

Broca’s area: this small area on the left side of the brain (sometimes on the right in left-handed individuals) is important in language processing. When damaged, an individual finds it difficult to speak but can still understand speech. Stuttering is sometimes associated with an underactive Broca’s area.

Corpus callosum: a broad band of nerve fibers that join the left and right hemispheres. It is the largest white matter structure in the brain and allows the two hemispheres to communicate. Dyslexic children have smaller corpus callosums; left-handed people, ambidextrous people, and musicians typically have larger ones.

Medulla oblongata: extending below the skull, it is involved in involuntary functions, such as vomiting, breathing, sneezing, and maintaining the correct blood pressure.

Hypothalamus: sitting just above the brain stem and roughly the size of an almond, the hypothalamus secretes a number of neurohormones and influences body temperature control, thirst, and hunger.

Thalamus: positioned in the center of the brain, the thalamus receives sensory and motor input and relays it to the rest of the cerebral cortex. It is involved in the regulation of consciousness, sleep, awareness, and alertness.

Amygdala: two almond-shaped nuclei deep within the temporal lobe. They are involved in decision-making, memory, and emotional responses; particularly negative emotions.

Share on PinterestThe spinal cord carries information from the brain to the rest of the body.

The spinal cord, running almost the full length of the back, carries information between the brain and body, but also carries out other tasks.

From the brainstem, where the spinal cord meets the brain, 31 spinal nerves enter the cord.

Along its length, it connects with the nerves of the peripheral nervous system (PNS) that run in from the skin, muscles, and joints.

Motor commands from the brain travel from the spine to the muscles and sensory information travels from the sensory tissues — such as the skin — toward the spinal cord and finally up to the brain.

The spinal cord contains circuits that control certain reflexive responses, such as the involuntary movement your arm might make if your finger was to touch a flame.

The circuits within the spine can also generate more complex movements such as walking. Even without input from the brain, the spinal nerves can coordinate all of the muscles necessary to walk. For instance, if the brain of a cat is separated from its spine so that its brain has no contact with its body, it will start spontaneously walking when placed on a treadmill. The brain is only required to stop and start the process, or make changes if, for instance, an object appears in your path.

The CNS can be roughly divided into white and gray matter. As a very general rule, the brain consists of an outer cortex of gray matter and an inner area housing tracts of white matter.

Both types of tissue contain glial cells, which protect and support neurons. White matter mostly consists of axons (nerve projections) and oligodendrocytes — a type of glial cell — whereas gray matter consists predominantly of neurons.

Also called neuroglia, glial cells are often called support cells for neurons. In the brain, they outnumber nerve cells 10 to 1.

Without glial cells, developing nerves often lose their way and struggle to form functioning synapses.

Glial cells are found in both the CNS and PNS but each system has different types. The following are brief descriptions of the CNS glial cell types:

Astrocytes: these cells have numerous projections and anchor neurons to their blood supply. They also regulate the local environment by removing excess ions and recycling neurotransmitters.

Oligodendrocytes: responsible for creating the myelin sheath — this thin layer coats nerve cells, allowing them to send signals quickly and efficiently.

Ependymal cells: lining the spinal cord and the brain’s ventricles (fluid-filled spaces), these create and secrete cerebrospinal fluid (CSF) and keep it circulating using their whip-like cilia.

Radial glia: act as scaffolding for new nerve cells during the creation of the embryo’s nervous system.

The cranial nerves are 12 pairs of nerves that arise directly from the brain and pass through holes in the skull rather than traveling along the spinal cord. These nerves collect and send information between the brain and parts of the body – mostly the neck and head.

Of these 12 pairs, the olfactory and optic nerves arise from the forebrain and are considered part of the central nervous system:

Olfactory nerves (cranial nerve I): transmit information about odors from the upper section of the nasal cavity to the olfactory bulbs on the base of the brain.

Optic nerves (cranial nerve II): carry visual information from the retina to the primary visual nuclei of the brain. Each optic nerve consists of around 1.7 million nerve fibers.

Below are the major causes of disorders that affect the CNS:

Trauma: depending on the site of the injury, symptoms can vary widely from paralysis to mood disorders.

Infections: some micro-organisms and viruses can invade the CNS; these include fungi, such as cryptococcal meningitis; protozoa, including malaria; bacteria, as is the case with leprosy, or viruses.

Degeneration: in some cases, the spinal cord or brain can degenerate. One example is Parkinson’s disease which involves the gradual degeneration of dopamine-producing cells in the basal ganglia.

Structural defects: the most common examples are birth defects; including anencephaly, where parts of the skull, brain, and scalp are missing at birth.

Tumors: both cancerous and noncancerous tumors can impact parts of the central nervous system. Both types can cause damage and yield an array of symptoms depending on where they develop.

Autoimmune disorders: in some cases, an individual’s immune system can mount an attack on healthy cells. For instance, acute disseminated encephalomyelitis is characterized by an immune response against the brain and spinal cord, attacking myelin (the nerves’ insulation) and, therefore, destroying white matter.

Stroke: a stroke is an interruption of blood supply to the brain; the resulting lack of oxygen causes tissue to die in the affected area.

Difference between the CNS and peripheral nervous system

The term peripheral nervous system (PNS) refers to any part of the nervous system that lies outside of the brain and spinal cord. The CNS is separate from the peripheral nervous system, although the two systems are interconnected.

There are a number of differences between the CNS and PNS; one difference is the size of the cells. The nerve axons of the CNS — the slender projections of nerve cells that carry impulses — are much shorter. PNS nerve axons can be up to 1 meter long (for instance, the nerve that activates the big toe) whereas, within the CNS, they are rarely longer than a few millimeters.

Another major difference between the CNS and PNS involves regeneration (regrowth of cells). Much of the PNS has the ability to regenerate; if a nerve in your finger is severed, it can regrow. The CNS, however, does not have this ability.

The components of the central nervous system are further split into a myriad of parts. Below, we will describe some of these sections in a little more detail.

How the spinal cord works

What is the central nervous system?

The central nervous system (CNS) controls most functions of the body and mind. It consists of two parts: the brain and the spinal cord.

The brain is the center of our thoughts, the interpreter of our external environment, and the origin of control over body movement. Like a central computer, it interprets information from our eyes (sight), ears (sound), nose (smell), tongue (taste), and skin (touch), as well as from internal organs such as the stomach.

The spinal cord is the highway for communication between the body and the brain. When the spinal cord is injured, the exchange of information between the brain and other parts of the body is disrupted.

How does the central nervous system differ from other systems of the body?

Most systems and organs of the body control just one function, but the central nervous system does many jobs at the same time. It controls all voluntary movement, such as speech and walking, and involuntary movements, such as blinking and breathing. It is also the core of our thoughts, perceptions, and emotions.

How does the central nervous system protect itself from injury?

The central nervous system is better protected than any other system or organ in the body. Its main line of defense is the bones of the skull and spinal column, which create a hard physical barrier to injury. A fluid-filled space below the bones, called the syrnix, provides shock absorbance.

Unfortunately, this protection can be a double-edged sword. When an injury to the central nervous system occurs, the soft tissue of the brain and spinal cord swells, causing pressure because of the confined space. The swelling makes the injury worse unless it is rapidly relieved. Fractured bones can lead to further damage and the possibility of infection.

Why can’t the central nervous system repair itself after injury?

Many organs and tissues in the body can recover after injury without intervention. Unfortunately, some cells of the central nervous system are so specialized that they cannot divide and create new cells. As a result, recovery from a brain or spinal cord injury is much more difficult.

The complexity of the central nervous system makes the formation of the right connections between brain and spinal cord cells very difficult. It is a huge challenge for scientists to recreate the central nervous system that existed before the injury.

Cells of the central nervous system

Neurons connect with one another to send and receive messages in the brain and spinal cord. Many neurons working together are responsible for every decision made, every emotion or sensation felt, and every action taken.

The complexity of the central nervous system is amazing: there are approximately 100 billion neurons in the brain and spinal cord combined. As many as 10,000 different subtypes of neurons have been identified, each specialized to send and receive certain types of information. Each neuron is made up of a cell body, which houses the nucleus. Axons and dendrites form extensions from the cell body.

Astrocytes, a kind of glial cell, are the primary support cells of the brain and spinal cord. They make and secrete proteins called neurotrophic factors. They also break down and remove proteins or chemicals that might be harmful to neurons (for example, glutamate, a neurotransmitter that in excess causes cells to become overexcited and die by a process called excitotoxicity).

Astrocytes aren’t always beneficial: after injury, they divide to make new cells that surround the injury site, forming a glial scar that is a barrier to regenerating axons.

Microglia are immune cells for the brain. After injury, they migrate to the site of injury to help clear away dead and dying cells. They can also produce small molecules called cytokines that trigger cells of the immune system to respond to the injury site. This clean-up process is likely to play an important role in recovery of function following a spinal injury.

Oligodendrocytes are glial cells that produce a fatty substance called myelin which wraps around axons in layers. Axon fibers insulated by myelin can carry electrical messages (also called action potentials) at a speed of 100 meters per second, while fibers without myelin can only carry messages at a speed of one meter per second.

Synapses and neurotransmission

Messages are passed from neuron to neuron through synapses, small gaps between the cells, with the help of chemicals called neurotransmitters. To transmit an action potential message across a synapse, neurotransmitter molecules are released from one neuron (the “pre-synaptic” neuron) across the gap to the next neuron (the “post-synaptic” neuron). The process continues until the message reaches its destination.

There are millions and millions of connections between neurons within the spinal cord alone. These connections are made during development, using positive (neurotrophic factors) and negative (inhibitory proteins) signals to fine-tune them. Amazingly, a single axon can form synapses with as many as 1,000 other neurons.

What causes paralysis?

There is a logical and physical topographical organization to the anatomy of the central nervous system, which is an elaborate web of closely connected neural pathways. This ordered relationship means that different segmental levels of the cord control different things, and injury to a particular part of the cord will have an impact on neighboring parts of the body.

Paralysis occurs when communication between the brain and spinal cord fails. This can result from injury to neurons in the brain (a stroke), or in the spinal cord. Trauma to the spinal cord affects only the areas below the level of injury. However, poliomyelitis (a viral infection) or Lou Gehrig’s disease (amyotrophic lateral sclerosis, or ALS) can affect neurons in the entire spinal cord.

The information pathways

Specialized neurons carry messages from the skin, muscles, joints, and internal organs to the spinal cord about pain, temperature, touch, vibration, and proprioception. These messages are then relayed to the brain along one of two pathways: the spinothalmic tract and the lemniscal pathway. These pathways are in different locations in the spinal cord, so an injury might not affect them in the same way or to the same degree.

Each segment of the spinal cord receives sensory input from a particular region of the body. Scientists have mapped these areas and determined the “receptive” fields for each level of the spinal cord. Neighboring fields overlap each other, so the lines on the diagram are approximate.

Voluntary and involuntary movement

Over one million axons travel through the spinal cord, including the longest axons in the central nervous system.

Neurons in the motor cortex, the region of the brain that controls voluntary movement, send their axons through the corticospinal tract to connect with motor neurons in the spinal cord. The spinal motor neurons project out of the cord to the correct muscles via the ventral root. These connections control conscious movements, such as writing and running.

Information also flows in the opposite direction resulting in involuntary movement. Sensory neurons provide feedback to the brain via the dorsal root. Some of this sensory information is conveyed directly to lower motor neurons before it reaches the brain, resulting in involuntary, or reflex movements. The remaining sensory information travels back to the cortex.

How the spinal cord and muscles work together

The spinal cord is divided into five sections: the cervical, thoracic, lumbar, sacral, and coccygeal regions. The level of injury determines the extent of paralysis and/or loss of sensation. No two injuries are alike.

This diagram illustrates the connections between the major skeletal muscle groups and each level of the spinal cord. A similar organization exists for the spinal control of the internal organs.

How the spinal cord and internal organs work together

In addition to the control of voluntary movement, the central nervous system contains the sympathetic and parasympathetic pathways that control the “fight or flight” response to danger and regulation of bodily functions. These include hormone release, movement of food through the stomach and intestines, and the sensations from and muscular control to all internal organs.

This diagram illustrates these pathways and the level of the spinal cord projecting to each organ.

What happens following a spinal cord injury?

A common set of biological events take place following spinal cord injury:

  1. Cells from the immune system migrate to the injury site, causing additional damage to some neurons and death to others that survived the initial trauma.
  2. The death of oligodendrocytes causes axons to lose their myelination, which greatly impairs the conduction of action potential, messages, or renders the remaining connections useless. The neuronal information highway is further disrupted because many axons are severed, cutting off the lines of communication between the brain and muscles and between the body’s sensory systems and the brain.
  3. Within several weeks of the initial injury, the area of tissue damage has been cleared away by microglia, and a fluid-filled cavity surrounded by a glial scar is left behind. Molecules that inhibit regrowth of severed axons are now expressed at this site. The cavitation is called a syrinx, which acts as a barrier to the reconnection of the two sides of the damaged spinal cord.

Although spinal cord injury causes complex damage, a surprising amount of the basic circuitry to control movement and process information can remain intact. This is because the spinal cord is arranged in layers of circuitry. Many of the connections and neuronal cell bodies forming this circuitry above and below the site of injury survive the trauma. An important question to research scientists is, how much do these surviving neurons “know?” Can they regenerate and make new, correct connections?

Intervention strategies

Research points to a multiplicity of possible interventions to promote recovery from a spinal injury. Some would be delivered immediately following the injury; others are less time-specific and involve rebuilding and reconnecting the injured cord. Clearly, both approaches are important: limiting degeneration will enhance the probability of greater recovery, while stimulating regeneration will build upon the remaining system to restore lost connectivity and perhaps to prevent further degeneration.

The following are some of the intervention strategies supported by funding from the Christopher & Dana Reeve Foundation. This is not a comprehensive list of all possible interventions.

Treatments immediately following an accident:

  1. Limiting initial degeneration

    Recent research has shown that there are at least three different mechanisms of cell death at play in neuronal and oligodendrocyte loss after injury: necrosis, excitotoxicity, and apoptosis.
  2. Treating inflammation

    Soon after injury, the spinal cord swells and proteins from the immune system invade the injured zone. This swelling and inflammation may foster secondary damage to the cord after the initial injury. So it is important to treat the inflammatory response as quickly as possible. Labs pursuing this approach include the Schwab Lab.

Longer-term treatments:

  1. Stimulating axonal growth

    Nerve fertilizers called neurotrophins can promote cell survival by blocking apoptosis and stimulate axonal growth. Each neurotrophin has a very specific target cell function. Some selectively prevent oligodendrocyte cell death, others promote axon regrowth or neuron survival, and still others serve multiple functions. Labs pursuing this approach include the Black Lab and the Parada Lab.
  2. Promoting new growth through substrate or guidance molecules

    Substrate and guidance molecules may improve targeting once axons have been encouraged to regenerate past the lesion site. These proteins act as roadmaps, steering axons to their correct targets. This is a critical function because even if axons do survive, they must reconnect with the correct targets. Labs pursuing this approach include the Black Lab, the Mendell Lab, and the Parada Lab.
  3. Blocking molecules that inhibit regeneration

    There are molecules within the brain and spinal cord that prevent neurons from dividing and axons from growing. Overcoming inhibition can stimulate axonal regrowth and regeneration and is likely to be an important component of regenerative therapies. The Schwab Lab is pursuing this approach.
  4. Supplying new cells to replace lost ones

    Stem cells, which are isolated from the CNS and can divide to form new cells, may replace lost neurons and gila. These stem cells must be harvested, treated to encourage growth, and then injected into the injured cord. Labs pursuing such an approach include the Bunge Lab and the Gage Lab.
  5. Building bridges to span the lesion cavity

    Bridges may be needed to reconnect the severed sections of the injured spinal cord. Scientists must determine how best to build these bridges and what molecules to use to encourage new growth and enhance survival of new connections. The Bunge Lab is pursuing this approach.

The Central Nervous System

The Central Nervous System

This page outlines the basic physiology of the central nervous system,
including the brain and spinal cord.
Separate pages describe the nervous system in
sensation, control of
skeletal muscle and control of internal

  1. The central nervous system CNS is responsible for integrating sensory
    information and responding accordingly. It consists of two main

    1. The spinal cord serves as a conduit for signals between the brain
      and the rest of the body. It also controls simple musculoskeletal
      reflexes without input from the brain.
    2. The brain is responsible for integrating most sensory
      information and coordinating body function, both consciously and
      unconsciously. Complex functions such as thinking and feeling as
      well as regulation of homeostasis are attributable to different
      parts of the brain.
  2. The brain and spinal cord share some key anatomic features:

    1. Living nervous tissue has the consistency of jelly and requires
      special protection from physical damage. The entire CNS is encased in bone.
      The brain
      is within the cranium, while the spinal cord runs within a
      canal through the vertebrae.
    2. Within its bony case, the entire CNS is bathed in a cerebrospinal
      fluid (CSF)
      , a colorless fluid produced by special structures in the brain.
      CSF provides a special chemical environment for nervous tissue, as well
      as an additional buffer against physical damage.
    3. The special chemical environment of nervous tissue is maintained by the
      relatively impermeable membranes of capillaries in the CNS. This feature
      is known as the blood-brain barrier.
    4. There are two general types of tissue in the CNS:

      1. Gray matter consists of nerve cell bodies, dendrites, and axons.
        Neurons in gray matter organize either in layers, as in the cerebral cortex,
        or as clusters called nuclei.
      2. White matter consists mostly of axons, causing it to look white
        due to the myelin sheathing of the axons.
  3. In the early embryo, the CNS forms as a relatively uniform tube. The
    major regions of the brain develop as enlargements at the head end of
    this tube:

    1. The medulla oblongata appears as a swelling at the upper end of
      the spinal cord. Besides being a conduit for fibers running between the
      spinal cord and higher regions of the brain, it contains control centers
      for involuntary functions such as blood pressure, breathing, swallowing
      and vomiting.
    2. Just above the medulla are the pons and cerebellum. The
      pons relays information between higher regions of the brain and the
      cerebellum, which processes sensory information and helps coordinate movement.
    3. The next segment, the midbrain, is primarily responsible for eye
    4. Above the midbrain lies the diencephalon, which is composed of
      two major parts:

      1. The thalamus processes and integrates all sensory information
        going to the higher regions of the brain.
      2. The hypothalamus is critical for homeostasis, the maintenance of
        the body’s internal environment. It influences nervous control of
        all internal organs and also serves as the master regulator of endocrine
        function by its control over the pituitary gland.
    5. The highest region of the brain is the cerebrum, which includes both
      the cerebral cortex that is visible on the outside of the brain as well
      as other internal structures. The cerebrum is responsible for conscious
      sensation and voluntary movement, as well as advanced functions such
      as thinking, learning and emotion.

Parts of the Nervous System

The two halves of the nervous system work together in order for your body to properly communicate its sensations and needs.

The nervous system has two great divisions: the central nervous system (CNS), which consists of the brain and the spinal cord, and the peripheral nervous system (PNS), which consists of nerves and small concentrations of gray matter called ganglia. The brain sends messages via the spinal cord to the body’s peripheral nerves, which control the muscles and internal organs.

Illustration by Lydia V. Kibiuk, Baltimore, MD

The forebrain, midbrain, hindbrain, and spinal cord form the central nervous system (CNS), which is one of two great divisions of the nervous system as a whole. The brain is protected by the skull, while the spinal cord, which is about 17 inches (43 cm) long, is protected by the vertebral column.

The other great division of the human brain is the peripheral nervous system (PNS), which consists of nerves and small concentrations of gray matter called ganglia, a term specifically used to describe structures in the PNS. Overall the nervous system is a vast biological computing device formed by a network of gray matter regions interconnected by white matter tracts.

The brain sends messages via the spinal cord to peripheral nerves throughout the body that serve to control the muscles and internal organs. The somatic nervous system is made up of neurons connecting the CNS with the parts of the body that interact with the outside world. Somatic nerves in the cervical region are related to the neck and arms; those in the thoracic region serve the chest; and those in the lumbar and sacral regions interact with the legs.

The autonomic nervous system is made of neurons connecting the CNS with internal organs. It is divided into two parts. The sympathetic nervous system mobilizes energy and resources during times of stress and arousal, while the parasympathetic nervous system conserves energy and resources during relaxed states, including sleep.

Messages are carried throughout the nervous system by the individual units of its circuitry: neurons.

The Nervous System | Boundless Psychology

Introduction to the Nervous System

The nervous system controls bodily function by gathering sensory input, integrating that information internally, and communicating proper motor output.

Learning Objectives

Describe the hierarchical structure of the nervous system

Key Takeaways

Key Points
  • The nervous system is the body’s main communication system; it gathers, synthesizes, and uses data from the environment.
  • The most basic unit of the nervous system is the neuron, which serves as both a sensor and communicator of internal and external stimuli.
  • The nervous system can be broken down into two major parts—the central nervous system and the peripheral nervous system.
  • The central nervous system, the main data center of the body, includes the brain and spinal cord.
  • The peripheral nervous system includes all of the neurons that sense and communicate data to the central nervous system.
  • The peripheral nervous system can be further divided into the autonomic system, which regulates involuntary actions, and the somatic system, which controls voluntary actions.
Key Terms
  • central nervous system: In vertebrates, the part of the nervous system comprising the brain, brainstem, and spinal cord.
  • peripheral nervous system: The part of the nervous system comprising a large system of nerves that are linked to the brain and spinal cord; this system is divided into the autonomic and somatic nervous systems.
  • neuron: A cell of the nervous system, which conducts nerve impulses; consisting of an axon and several dendrites. Neurons are connected by synapses.
  • innervate: To supply nerves to a tissue.

The nervous system allows organisms to sense, organize, and react to information in the environment. The basic unit of the nervous system is the neuron. Synapses form between the neurons, allowing them to communicate to other neurons or other systems in the body. The general flow of information is that the peripheral nervous system (PNS) takes in information through sensory neurons, then sends it to the central nervous system (CNS) to be processed. After processing, the CNS “tells” the PNS what to do—what muscles to flex, whether the lungs need more oxygen, which limbs need more blood, any number of biological processes—and the PNS makes it happen through muscle control. The neurons responsible for taking information to the CNS are known as afferent neurons, while the neurons that carry the responses from the CNS to the PNS are known as efferent neurons.

The human nervous system: The nervous system of the human body, including the brain and spinal cord (central nervous system) and all the nerves of the body (peripheral nervous system).

The nervous system can be divided into two major parts—the central nervous system (CNS) and the peripheral nervous system (PNS).

Central Nervous System

The central nervous system includes the spinal cord and the brain. The brain is the body’s main control center. The main function of the CNS is the integration and processing of sensory information. It synthesizes sensory input to compute an appropriate motor response, or output.

Peripheral Nervous System

The peripheral nervous system includes a large system of nerves that are linked to the brain and spinal cord. It is comprised of sensory receptors, which process changes in internal and external stimuli and communicate that information to the CNS. The PNS can be further subdivided into the autonomic nervous system and the somatic nervous system.

Autonomic Nervous System

The autonomic nervous system regulates involuntary actions such as internal-organ function and blood-vessel movement. It supplies nerves to (“innervates”) cardiac and smooth muscle tissue. The autonomic nervous system is made of two components, which work in opposition to one another: the sympathetic nervous system, responsible for the body’s “fight-or-flight” response to danger, and the parasympathetic nervous system, which calms the body back down.

Somatic Nervous System

The somatic nervous system controls voluntary movements such as those in the skin, bones, joints, and skeletal muscles.

Both of these systems within the PNS work together with the CNS to regulate bodily function and provide reactions to external stimuli.

The Central Nervous System (CNS)

The central nervous system is made up of the brain and spinal cord, which process sensory input and provide instructions to the body.

Learning Objectives

Describe the structural elements of the central nervous system

Key Takeaways

Key Points
  • The central nervous system (CNS) and the peripheral nervous system (PNS) comprise the entirety of the body’s nervous system, which regulates and maintains its most basic functions.
  • The CNS is the main control center of the body—it takes in sensory information, organizes and synthesizes this input, then provides instructions for motor output to the rest of the body.
  • The CNS is made up of the brain and spinal cord.
  • The brain is the main data center of the body, consisting of the cerebrum (which regulates higher-level functioning such as thought) and the cerebellum (which maintains coordination).
  • The brain stem includes the midbrain, pons, and medulla, and controls lower-level functioning such as respiration and digestion.
  • The spinal cord connects the brain and the body’s main receptors, and serves as a conduit for sensory input and motor output.
Key Terms
  • cerebrum: In humans it is the largest part of the brain and is the seat of motor and sensory functions, as well as the higher mental functions such as consciousness, thought, reason, emotion, and memory.
  • spinal cord: A thick, whitish cord of nerve tissue that is a major part of the central nervous system. It extends from the brain stem through the spine, with nerves branching off to various parts of the body.
  • cerebellum: Part of the hindbrain in vertebrates. In humans it lies between the brainstem and the cerebrum, and plays an important role in sensory perception, motor output, balance, and posture.
  • brain stem: The part of the brain that connects the spinal cord to the forebrain and cerebrum.

Introduction to the Central Nervous System

The central nervous system (CNS) is one of the two major subdivisions of the nervous system. The CNS includes the brain and spinal cord, which together comprise the body’s main control center. Together with the peripheral nervous system (PNS), the CNS performs fundamental functions that contribute to an organism’s life and behavior.

Activity of the CNS

The nervous system has three main functions: gathering sensory information from external stimuli, synthesizing that information, and responding to those stimuli. The CNS is mainly devoted to the “information synthesizing” function. During this step in the process, the brain and spinal cord decide on appropriate motor output, which is computed based on the type of sensory input. The CNS regulates everything from organ function to high-level thought to purposeful body movement. Thus, the CNS is commonly thought of as the control center of the body.

Structure of the Central Nervous System

The CNS is comprised of the brain, brain stem, and spinal cord.

The central nervous system: The three major components of the central nervous system: 1) the brain, 2) brain stem, and 3) spinal cord.


The brain is found in the cranial cavity and consists of the cerebrum and cerebellum. It houses the nerve centers responsible for coordinating sensory and motor systems in the body. The cerebrum, or the top portion for the brain, is the seat of higher-level thought. It is comprised of two hemispheres, each controlling the opposite side of the body. Each of these hemispheres is divided into four separate lobes:

  • the frontal lobe, which controls specialized motor control, learning, planning, and speech;
  • the parietal lobe, which controls somatic or voluntary sensory functions;
  • the occipital lobe, which controls vision;
  • the temporal lobe, which controls hearing and some other speech functions.

The cerebellum is located underneath the backside of the cerebrum, and governs balance and fine motor movements. Its main function is maintaining coordination throughout the body.

Brain Stem

The brain stem is connected to the underside of the brain. It consists of the midbrain, pons, and medulla. The midbrain is found in between the hindbrain and the forebrain. It regulates motor function and allows motor and sensory information to pass from the brain to the rest of the body. The pons houses the control centers for respiration and inhibitory functions. The medulla also helps regulate respiration, as well as cardiovascular and digestive functioning.

Spinal Cord

The spinal cord connects the brain and brain stem to all of the major nerves in the body. Spinal nerves originate from the spinal cord and control the functions of the rest of the body. Impulses are sent from receptors through the spinal cord to the brain, where they are processed and synthesized into instructions for the rest of the body. This data is then sent back through the spinal cord to muscles and glands for motor output.

The Peripheral Nervous System (PNS)

The peripheral nervous system connects the central nervous system to environmental stimuli to gather sensory input and create motor output.

Learning Objectives

Discuss the organization of the peripheral nervous system

Key Takeaways

Key Points
  • The peripheral nervous system (PNS) provides the connection between internal or external stimuli and the central nervous system to allow the body to respond to its environment.
  • The PNS is made up of different kinds of neurons, or nerve cells, which communicate with each other through electric signaling and neurotransmitters.
  • The PNS can be broken down into two systems: the autonomic nervous system, which regulates involuntary actions such as breathing and digestion, and the somatic nervous system, which governs voluntary action and body reflexes.
  • The autonomic nervous system has two complementary parts: the sympathetic nervous system, which activates the “fight-or-flight-or-freeze” stress response, and the parasympathetic nervous system, which reacts with the “rest-and-digest” response after stress.
  • The somatic nervous system coordinates voluntary physical action. It is also responsible for our reflexes, which do not require brain input.
Key Terms
  • afferent: Leading toward the central nervous system.
  • efferent: Leading away from the central nervous system.
  • polysynaptic reflex: Involves at least one interneuron between the sensory and motor neurons.
  • monosynaptic reflex: Involves a single synapse between the sensory neuron that receives the information and the motor neuron that responds.
  • somatic nervous system: The part of the peripheral nervous system that transmits signals from the central nervous system to skeletal muscle and from receptors of external stimuli to the central nervous system, thereby mediating sight, hearing, and touch.
  • autonomic nervous system: The part of the nervous system that regulates the involuntary activity of the heart, intestines, and glands, including digestion, respiration, perspiration, metabolism, and blood-pressure modulation.
  • sympathetic nervous system: The part of the autonomic nervous system that raises blood pressure and heart rate, constricts blood vessels, and dilates the pupils in situations of stress.
  • parasympathetic nervous system: One of the divisions of the autonomic nervous system; located between the brain and the spinal cord; slows the heart and relaxes the muscles.

The peripheral nervous system (PNS) is one of the two major components of the body’s nervous system. In conjunction with the central nervous system (CNS), the PNS coordinates action and responses by sending signals from one part of the body to another. The CNS includes the brain, brain stem, and spinal cord, while the PNS includes all other sensory neurons, clusters of neurons called ganglia, and connector neurons that attach to the CNS and other neurons.

The nervous system: The human nervous system, including both the central nervous system (in red: brain, brain stem, and spinal cord) and the peripheral nervous system (in blue: all other neurons and receptors).

Divisions of the Peripheral Nervous System

The PNS can also be divided into two separate systems: the autonomic nervous system and the somatic nervous system.

Autonomic Nervous System

The autonomic nervous system regulates involuntary and unconscious actions, such as internal-organ function, breathing, digestion, and heartbeat. This system consists of two complementary parts: the sympathetic and parasympathetic systems. Both divisions work without conscious effort and have similar nerve pathways, but they generally have opposite effects on target tissues.

The sympathetic nervous system activates the “fight or flight” response under sudden or stressful circumstances, such as taking an exam or seeing a bear. It increases physical arousal levels, raising the heart and breathing rates and dilating the pupils, as it prepares the body to run or confront danger. These are not the only two options; “fight or flight” is perhaps better phrased as “fight or flight or freeze,” where in the third option the body stiffens and action cannot be taken. This is an autonomic response that occurs in animals and humans; it is a survival mechanism thought to be related to playing dead when attacked by a predator. Post-traumatic stress disorder (PTSD) can result when a human experiences this “fight or flight or freeze” mode with great intensity or for large amounts of time.

The parasympathetic nervous system activates a “rest and digest” or “feed and breed” response after these stressful events, which conserves energy and replenishes the system. It reduces bodily arousal, slowing the heartbeat and breathing rate. Together, these two systems maintain homeostasis within the body: one priming the body for action, and the other repairing the body afterward.

Somatic Nervous System

The somatic nervous system keeps the body adept and coordinated, both through reflexes and voluntary action. The somatic nervous system controls systems in areas as diverse as the skin, bones, joints, and skeletal muscles. Afferent fibers, or nerves that receive information from external stimuli, carry sensory information through pathways that connect the skin and skeletal muscles to the CNS for processing. The information is then sent back via efferent nerves, or nerves that carry instructions from the CNS, back through the somatic system. These instructions go to neuromuscular junctions—the interfaces between neurons and muscles—for motor output.

The somatic system also provides us with reflexes, which are automatic and do not require input or integration from the brain to perform. Reflexes can be categorized as either monosynaptic or polysynaptic based on the reflex arc used to perform the function. Monosynaptic reflex arcs, such as the knee-jerk reflex, have only a single synapse between the sensory neuron that receives the information and the motor neuron that responds. Polysynaptic reflex arcs, by contrast, have at least one interneuron between the sensory neuron and the motor neuron. An example of a polysynaptic reflex arc is seen when a person steps on a tack—in response, their body must pull that foot up while simultaneously transferring balance to the other leg.

Overview, Gross Anatomy, Microscopic Anatomy

A motor unit consists of an anterior horn cell, its motor axon, the muscle fibers it innervates, and the connection between them (neuromuscular junction). The anterior horn cells are located in the gray matter of the spinal cord and thus are technically part of the CNS. In contrast to the motor system, the cell bodies of the afferent sensory fibers lie outside the spinal cord, in posterior root ganglia.

Nerve fibers outside the spinal cord join to form anterior (ventral) motor roots and posterior (dorsal) sensory root nerve roots. The anterior and posterior roots combine to form a spinal nerve. Thirty of the 31 pairs of spinal nerves have anterior and posterior roots; C1 has no sensory root.

The spinal nerves exit the vertebral column via an intervertebral foramen. Because the spinal cord is shorter than the vertebral column, the more caudal the spinal nerve, the further the foramen is from the corresponding cord segment. Thus, in the lumbosacral region, nerve roots from lower cord segments descend within the spinal column in a near-vertical sheaf, forming the cauda equina. Just beyond the intervertebral foramen, spinal nerves branch into several parts.

Branches of the cervical and lumbosacral spinal nerves anastomose peripherally into plexuses, then branch into nerve trunks that terminate up to 1 μm away in peripheral structures. The intercostal nerves are segmental.

The term peripheral nerve refers to the part of a spinal nerve distal to the nerve roots. Peripheral nerves are bundles of nerve fibers. They range in diameter from 0.3-22 μm. Schwann cells form a thin cytoplasmic tube around each fiber and further wrap larger fibers in a multilayered insulating membrane (myelin sheath).

Peripheral nerves have multiple layers of connective tissue surrounding axons, with the endoneurium surrounding individual axons, perineurium binding axons into fascicles, and epineurium binding the fascicles into a nerve. Blood vessels (vasa vasorum) and nerves (nervi nervorum) are also contained within the nerve. Nerve fibers in peripheral nerves are wavy, such that a length of peripheral nerve can be stretched to half again its length before tension is directly transmitted to nerve fibers. Nerve roots have much less connective tissue, and individual nerve fibers within the roots are straight, leading to some vulnerability.

Peripheral nerves receive collateral arterial branches from adjacent arteries. These arteries that contribute to the vasa nervorum anastomose with arterial branches entering the nerve above and below in order to provide an uninterrupted circulation along the course of the nerve.

Individual nerve fibers vary widely in diameter and may also be myelinated or unmyelinated. Myelin in the peripheral nervous system derives from Schwann cells, and the distance between nodes of Ranvier determines the conduction rate. Because certain conditions preferentially affect myelin, they would be most likely to affect the functions mediated by the largest, fastest, most heavily myelinated axons.

Sensory neurons are somewhat unique, having an axon that extends to the periphery and another axon that extends into the central nervous system via the posterior root. The cell body of this neuron is located in the posterior root ganglion or one of the sensory ganglia of sensory cranial nerves. Both the peripheral and the central axon attach to the neuron at the same point, and these sensory neurons are called “pseudounipolar” neurons.

Before a sensory signal can be relayed to the nervous system, it must be transduced into an electrical signal in a nerve fiber. This involves a process of opening ion channels in the membrane in response to mechanical deformation, temperature or, in the case of nociceptive fibers, signals released from damaged tissue. Many receptors become less sensitive with continued stimuli, and this is termed adaptation. This adaptation may be rapid or slow, with rapidly adapting receptors being specialized for detecting changing signals.

Several structural types of receptors exist in the skin. These fall into the category of encapsulated or nonencapsulated receptors. The nonencapsulated endings include free nerve endings, which are simply the peripheral end of the sensory axon. These mostly respond to noxious (pain) and thermal stimuli. Some specialized free nerve endings around hairs respond to very light touch; also, some free nerve endings contact special skin cells, called Merkel cells.

These Merkel cells (discs) are specialized cells that release transmitter onto peripheral sensory nerve terminals. The encapsulated endings include Meisner corpuscles, Pacinian corpuscles, and Ruffini endings. The capsules that surround encapsulated endings change the response characteristics of the nerves. Most encapsulated receptors are for touch, but the Pacinian corpuscles are very rapidly adapting and, therefore, are specialized to detect vibration. Ultimately, the intensity of the stimulus is encoded by the relative frequency of action potential generation in the sensory axon.

In addition to cutaneous receptors, muscle receptors are involved in detecting muscle stretch (muscle spindle) and muscle tension (Golgi tendon organs). Muscle spindles are located in the muscle bellies and consist of intrafusal muscle fibers that are arranged in parallel with most fibers comprising the muscle (ie, extrafusal fibers). The ends of the intrafusal fibers are contractile and are innervated by gamma motor neurons, while the central portion of the muscle spindle is clear and is wrapped by a sensory nerve ending, the annulospiral ending. This ending is activated by stretch of the muscle spindle or by contraction of the intrafusal fibers (see section V). The Golgi tendon organs are located at the myotendinous junction and consist of nerve fibers intertwined with the collagen fibers at the myotendinous junctions. They are activated by contraction of the muscle (muscle tension).

Both the sympathetic and parasympathetic portions of the autonomic nervous system have a 2-neuron pathway from the central nervous system to the peripheral organ. Therefore, a ganglion is interposed in each of these pathways, with the exception of the sympathetic pathway to the suprarenal (adrenal) medulla. The suprarenal medulla basically functions as a sympathetic ganglion. The 2 nerve fibers in the pathway are termed preganglionic and postganglionic. At the level of the autonomic ganglia, the neurotransmitter is typically acetylcholine. Postganglionic parasympathetic neurons also release acetylcholine, while norepinephrine is the postganglionic transmitter for most sympathetic nerve fibers. The exception is the use of acetylcholine in sympathetic transmission to the sweat glands and erector pili muscles as well as to some blood vessels in muscle.

Sympathetic preganglionic neurons are located between T1 and L2 in the lateral horn of the spinal cord. Therefore, sympathetics have been termed the “thoracolumbar outflow.” These preganglionic visceral motor fibers leave the cord in the anterior nerve root and then connect to the sympathetic chain through the white rami communicans. This chain of connected ganglia follows the sides of the vertebrae all the way from the head to the coccyx. These axons may synapse with postganglionic neurons in these paravertebral ganglia. Alternatively, preganglionic fibers can pass directly through the sympathetic chain to reach prevertebral ganglia along the aorta (via splanchnic nerves).

Additionally, these preganglionics can pass superiorly or inferiorly through the interganglionic rami in the sympathetic chain to reach the head or the lower lumbosacral regions. Sympathetic fibers can go to viscera by 1 of 2 pathways. Some postganglionic can leave the sympathetic chain and follow blood vessels to the organs. Alternatively, preganglionic fibers may pass directly through the sympathetic chain to enter the abdomen as splanchnic nerves. These synapse in ganglia located along the aorta (the celiac, aorticorenal, superior, or inferior mesenteric ganglia) with postganglionic. Again, postganglionics follow the blood vessels.

Sympathetic postganglionics from the sympathetic chain can go back to the spinal nerves (via gray rami communicans) to be distributed to somatic tissues of the limbs and body walls. For example, the somatic response to sympathetic activation will result in sweating, constriction of blood vessels in the skin, dilation of vessels in muscle and in piloerection. Damage to sympathetic nerves to the head results in slight constriction of the pupil, slight ptosis, and loss of sweating on that side of the head (called Horner syndrome). This can happen anywhere along the course of the nerve pathway including the upper thoracic spine and nerve roots, the apex of the lung, the neck or the carotid plexus of postganglionics.

Parasympathetic nerves arise with cranial nerves III, VII, IX, and X, as well as from the sacral segments S2-4. Therefore, they have been termed the “craniosacral outflow.” Parasympathetics in cranial nerve III synapse in the ciliary ganglion and are involved in pupillary constriction and accommodation for near vision. Parasympathetics in cranial nerve VII synapse in the pterygopalatine ganglion (lacrimation) or the submandibular ganglion (salivation), while those in cranial nerve IX synapse in the otic ganglion (salivation from parotid gland).

The vagus nerve follows a long course to supply the thoracic and abdominal organs up to the level of the distal transverse colon, synapsing in ganglia within the organ walls. The pelvic parasympathetics, which appear as the pelvic splanchnic nerves, activate bladder contraction and also supply lower abdominal and pelvic organs.


The myelin sheath enhances impulse conduction. The largest and most heavily myelinated fibers conduct quickly; they convey motor, touch, and proprioceptive impulses. The less myelinated and unmyelinated fibers conduct more slowly; they convey pain, temperature, and autonomic impulses. Because nerves are metabolically active tissues, they require nutrients, supplied by blood vessels called the vasa nervorum.

11.5: Central Nervous System – Biology LibreTexts


Figure \(\PageIndex{1}\) is a very odd-looking drawing and is called a homunculus. The mass represents a cross-sectional wedge of the human brain. The drawing shows some areas of the brain associated with different parts of the body. As you can see, larger areas of the brain in this region are associated with the hands, face, and tongue than the legs and feet. Given the importance of speech, manual dexterity, and face-to-face social interactions in human beings, it is not surprising that relatively large areas of the brain are needed to control these body parts. The brain is the most complex organ in the human body and part of the central nervous system.

Figure \(\PageIndex{1}\): Brain-Body Map. There’s a map of your body on your brain’s cortex, but the map is not proportional to actual space. Sensitive parts like the face and fingers are represented by more areas than less sensitive parts like the legs or back

What Is the Central Nervous System?

The central nervous system (CNS) is the part of the nervous system that includes the brain and spinal cord. Figure \(\PageIndex{2}\) shows the central nervous system as one of the two main divisions of the total nervous system. The other main division is the peripheral nervous system (PNS). The CNS and PNS work together to control virtually all body functions. You can read much more about the PNS in the concept Peripheral Nervous System.

The delicate nervous tissues of the central nervous system are protected by major physical and chemical barriers. Physically, the brain and spinal cord are surrounded by tough meninges, a three-layer protective sheath that also contains cushioning cerebrospinal fluid. The bones of the skull and spinal vertebrae also contribute to physically protecting the brain and spinal cord. Chemically, the brain and spinal cord are isolated from the circulation — and most toxins or pathogens in the blood — by the blood-brain barrier. The blood-brain barrier is a highly selective membrane formed of endothelial cells (a type of glial cells) that separates the circulating blood from the extracellular fluid in the CNS. The barrier allows water, certain gases, glucose, and some other molecules needed by the brain and spinal cord to cross from the blood into the CNS while keeping out potentially harmful substances. These physical and chemical barriers make the CNS less susceptible to injury. However, damage to the CNS is likely to have more serious consequences.

Figure \(\PageIndex{2}\): The two main parts of the central nervous system are the brain and the spinal cord. Ganglions and nerves are part of the peripheral nerve system.

The Brain

Figure \(\PageIndex{3}\): Cerebrum, Cerebellum, and Brain Stem are the major parts of the brain. the medulla is part of the brain stem.

The brain is the control center not only of the rest of the nervous system but of the entire organism. The adult brain makes up only about 2 percent of the body’s weight, but it uses about 20 percent of the body’s total energy. The brain contains an estimated one hundred billion neurons, and each neuron has thousands of synaptic connections to other neurons. The brain also has about the same number of glial cells as neurons. No wonder the brain uses so much energy! In addition, the brain uses mostly glucose for energy. As a result, if the brain is deprived of glucose, it can lead to unconsciousness. The brain is able to store some glucose in the form of glycogen, but in much smaller amounts than are found in the liver and skeletal muscles.

The brain controls such mental processes as reasoning, imagination, memory, and language. It also interprets information from the senses and commands the body how to respond. It controls basic physical processes such as breathing and heartbeat as well as voluntary activities such as walking and writing. The brain has three major parts: the cerebrum, cerebellum, and brain stem (Figure \(\PageIndex{3}\)). The figure shows the brain from the left side of the head. It shows how the brain would appear if the skull and meninges were removed. The brain stem via its medulla links to the spinal cord. The cerebellum is a small section at the back of the brain. The largest part of the brain is the cerebrum.


The cerebrum is the largest part of the brain. It controls conscious, intellectual functions. For example, it controls reasoning, language, memory, sight, touch, and hearing. When you read a book, play a video game, or recognize a classmate, you are using your cerebrum.

Hemispheres and Lateralization of the Cerebrum

The cerebrum is divided from front to back into two halves called the left and right hemispheres. The two hemispheres are connected by a thick bundle of axons, known as the corpus callosum, which lies deep within the brain. The corpus callosum is the main avenue of communication between the two hemispheres. It connects each point in the cerebrum to the mirror-image point in the opposite hemisphere.

The right and left hemispheres of the cerebrum are similar in shape, and most areas of the cerebrum are found in both hemispheres. Some areas, however, show lateralization, or a concentration in one hemisphere or the other. For example, in most people, language functions are more concentrated in the left hemisphere, whereas abstract reasoning and visual-spatial abilities are more concentrated in the right hemisphere.

For reasons that are not yet clear, each hemisphere of the brain interacts primarily with the opposite side of the body. The left side of the brain receives messages from and sends commands to the right side of the body, and the right side of the brain receives messages from and sends commands to the left side of the body. Sensory nerves from the spinal cord to the brain and motor nerves from the brain to the spinal cord both cross the midline of the body at the level of the brain stem.

Cerebral Cortex

Most of the information processing in the brain actually takes place in the cerebral cortex. This is a rind of gray matter and other tissues just a few millimeters thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it that greatly increase the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2(2.5 ft2). The size and importance of the cerebral cortex are far greater in the human brain than the brains of any other vertebrates including nonhuman primates.

Lobes of the Cerebral Cortex

Each hemisphere of the cerebrum is further divided into the four lobes shown in Figure \(\PageIndex{4}\) and described below.

1. The frontal lobes are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions such as attention, self-control, planning, problem-solving, reasoning, abstract thought, language, and personality.

Figure \(\PageIndex{4}\): Each hemisphere of the cerebrum consists of four parts, called lobes. The lobes are associated with multiple functions. The image shows one function of each lobe. Frontal, Parietal, Occipital, and Temporal lobes are associated with reasoning, touch, sight, and hearing, respectively.

2. The parietal lobes are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation, including temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.

3. The temporal lobes are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.

4. The occipital lobes are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to vision.

Inner Structures of the Brain

Several structures are located deep within the brain and are important for communication between the brain and spinal cord or the rest of the body. These structures include the hypothalamus and thalamus. Figure \(\PageIndex{5}\) shows where these structures are located in the brain. The cerebrum, hypothalamus, and thalamus exist in two halves, one in each hemisphere.

Figure \(\PageIndex{5}\): Just below the cerebrum is the thalamus. Hypothalamus is located below the thalamus and a little to the anterior. The pituitary gland is attached to the hypothalamus via a tube called the infundibulum.


The hypothalamus is located just above the brain stem and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the autonomic nervous system, including body temperature, heart rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.

One way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. For example, it synthesizes the hormone oxytocin, which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes the hormone vasopressin (also called antidiuretic hormone), which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see diagram above) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.

The main way the hypothalamus influences body functions is by controlling the pituitary gland, known as the master gland of the endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.


The thalamus, which is located near the hypothalamus (Figure \(\PageIndex{5}\)), is a major hub for information traveling back and forth between the spinal cord and cerebrum. It filters sensory information traveling to the cerebrum. It relays sensory signals to the cerebral cortex and motor signals to the spinal cord. It is also involved in the regulation of consciousness, sleep, and alertness.


The cerebellum is just below the cerebrum and at the back of the brain behind the brain stem (Figure \(\PageIndex{3}\)). It coordinates body movements and is involved in movements that are learned with repeated practice. For example, when you hit a softball with a bat or touch type on a keyboard you are using the cerebellum. Many nerve pathways link the cerebellum with motor neurons throughout the body.

Brain Stem

Sometimes called the “lower brain,” the brain stem is the lower part of the brain that is joined to the spinal cord. There are three parts to the brainstem: the midbrain, the pons, and the medulla oblongata, which are shown in Figure \(\PageIndex{6}\) below. The brain stem is primarily involved in the unconscious autonomic functions as well as several types of sensory information. It also helps coordinate large body movements such as walking and running. The midbrain deals with sight and sound information and translates these inputs before sending them to the forebrain. The pons relays messages to other parts of the brain (primarily the cerebrum and cerebellum) and helps regulate breathing. Some researchers have hypothesized that the pons plays a role in dreaming. Some of the functions of the Pons are shared by the medulla oblongata, also called the medulla. The medulla controls several subconscious homeostatic functions such as breathing, heart and blood vessel activity, swallowing, and digestion.

Figure \(\PageIndex{6}\): Brain stem includes the midbrain, pons, and medulla oblongata

One of the brain stem’s most important roles is that of an “information highway.” That is, all of the information coming from the body to the brain and the information from the cerebrum to the body go through the brain stem. Sensory pathways for such things as pain, temperature, touch, and pressure sensation go upward to the cerebrum, and motor pathways for movement and other body processes go downward to the spinal cord. Most of the axons in the motor pathways cross from one side of the CNS to the other as they pass through the medulla oblongata. As a result, the right side of the brain controls much of the movement on the left side of the body, and the left side of the brain controls much of the movement on the right side of the body.

Spinal Cord

Figure \(\PageIndex{7}\): The spinal cord (yellow) runs from the bottom of the brain to the lower back

The spinal cord is a long, thin, tubular bundle of nervous tissues that extends from the brain stem and continues down the center of the back to the pelvis. It is highlighted in yellow in Figure \(\PageIndex{7}\). The spinal cord is enclosed within but is shorter than, the vertebral column.

Structure of the Spinal Cord

The center of the spinal cord consists of gray matter, which is made up mainly of cell bodies of neurons, including interneurons and motor neurons. The gray matter is surrounded by white matter that consists mainly of myelinated axons of motor and sensory neurons. Spinal nerves, which connect the spinal cord to the PNS, exit from the spinal cord between vertebrae (Figure \(\PageIndex{8}\)).

Figure \(\PageIndex{8}\): This model shows three vertebrae (white) with branching spinal nerves (yellow) emerging from either side of the spinal cord between vertebrae

Functions of the Spinal Cord

Figure \(\PageIndex{9}\): This diagram shows what happens in a long reflex (top), in which sensory nerves carry the message all the way to the spinal cord; and in a short reflex (bottom), in which sensory nerves travel only to a ganglion outside the spinal cord. Note that interneurons are involved in reflexes, connecting sensory and motor neurons, but they are not actually shown in the diagram.

The spinal cord serves as an information superhighway. It passes messages from the body to the brain and from the brain to the body. Sensory (afferent) nerves carry nerve impulses to the brain from sensory receptor cells everywhere in and on the body. Motor (efferent) nerves carry nerve impulses away from the brain to glands, organs, or muscles throughout the body.

The spinal cord also independently controls certain rapid responses called reflexes without any input from the brain. You can see how this may happen in Figure \(\PageIndex{9}\). A sensory receptor responds to a sensation and sends a nerve impulse along a sensory nerve to the spinal cord. In the spinal cord, the message passes to an interneuron and from the interneuron to a motor nerve, which carries the impulse to a muscle. The muscle contracts in response. These neuron connections form a reflex arc, which requires no input from the brain. No doubt you have experienced such reflex actions yourself. For example, you may have reached out to touch a pot on the stove, not realizing that it was very hot. Virtually at the same moment that you feel the burning heat, you jerk your arm back and remove your hand from the pot.

Injuries to the Spinal Cord

Physical damage to the spinal cord may result in paralysis, which is a loss of sensation and movement in part of the body. Paralysis generally affects all the areas of the body below the level of the injury because nerve impulses are interrupted and can no longer travel back and forth between the brain and body beyond that point. If an injury to the spinal cord produces nothing more than swelling, the symptoms may be transient. However, if nerve fibers (axons) in the spinal cord are badly damaged, the loss of function may be permanent. Experimental studies have shown that spinal nerve fibers attempt to regrow, but tissue destruction usually produces scar tissue that cannot be penetrated by the regrowing nerves, as well as other factors that inhibit nerve fiber regrowth in the central nervous system.

Feature: My Human Body

Each year, many millions of people have a stroke, and stroke is the second leading cause of death in adults. Stroke, also known as cerebrovascular accident, occurs when poor blood flow to the brain results in the death of brain cells. There are two main types of strokes:

  • Ischemic strokes occur due to a lack of blood flow because of a blood clot in an artery going to the brain.
  • Hemorrhagic strokes occur due to bleeding from a broken blood vessel in the brain.

Either type of stroke may result in paralysis, loss of the ability to speak or comprehend speech, loss of bladder control, personality changes, and many other potential effects, depending on the part of the brain that is injured. The effects of a stroke may be mild and transient or more severe and permanent. A stroke may even be fatal. It generally depends on the type of stroke and how extensive it is.

Are you at risk of stroke? The main risk factor for stroke is age: about two-thirds of strokes occur in people over the age of 65. There is nothing you can do about your age, but most other stroke risk factors can be reduced with lifestyle changes or medications. The risk factors include high blood pressure, tobacco smoking, obesity, high blood cholesterol, diabetes mellitus, and atrial fibrillation.

Chances are good that you or someone you know is at risk of a stroke, so it is important to recognize a stroke if one occurs. Stoke is a medical emergency, and the more quickly treatment is given, the better the outcome is likely to be. In the case of ischemic strokes, the use of clot-busting drugs may prevent permanent brain damage if administered within 3 or 4 hours of the stroke. Remembering the signs of a stroke is easy.

They are summed up by the acronym FAST, as explained in the chart below.

Figure \(\PageIndex{10}\): The signs of stroke are abbreviated as FAST. Where F, A, S, and T stand for droopy face, arm weakness, slurry speak, and time fo call 911, respectively.


  1. What is the central nervous system?
  2. How is the central nervous system protected?
  3. What is the overall function of the brain?
  4. Identify the three main parts of the brain and one function of each part.
  5. Describe the hemispheres of the brain.
  6. Explain and give examples of lateralization of the brain.
  7. Identify one function of each of the four lobes of the cerebrum.
  8. Summarize the structure and function of the cerebral cortex.
  9. Explain how the hypothalamus controls the endocrine system.
  10. Describe the spinal cord.
  11. What is the main function of the spinal cord?
  12. Explain how reflex actions occur.
  13. Why do severe spinal cord injuries usually cause paralysis?
  14. What do you think are some possible consequences of severe damage to the brain stem? How might this compare to the consequences of severe damage to the frontal lobe? Explain your answer.
  15. Information travels very quickly in the nervous system, but generally, the longer the path between areas, the longer it takes. Based on this, explain why you think reflexes often occur at the spinal cord level and do not require input from the brain.

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More than 40 million people worldwide suffer from Alzheimer’s disease, a brain disorder, and the number is expected to grow dramatically in the coming decades. The disease was discovered more than a century ago, but little progress has been made in finding a cure. Watch this exciting TED talk in which scientist Samuel Cohen shares a new breakthrough in Alzheimer’s research as well as a message of hope that a cure for Alzheimer’s will be found.

90,000 Neurology: consultations, research in Vilnius

Neurology is the science that studies the structure and function of the nervous system. Doctors-neurologists conduct diagnostic studies of brain disorders, disorders of the nervous system, consult and treat patients suffering from diseases of the nervous system.

The most common neurological diseases include headaches, migraines, circulatory disorders of the brain, diseases of the central nervous system (multiple sclerosis, etc.), diseases of the degenerative nervous system (Alzheimer’s disease, Parkinson’s disease), diseases of the spine, epilepsy, insomnia and other diseases of the nervous system.

The central nervous system is represented by the spinal cord and the brain. As a rule, the following signs indicate disorders or damage to the nervous system: headache and dizziness, impaired movement and coordination of movements, impaired speech, memory, swallowing, vision and other senses. A thorough examination by a neurologist, analyzes, anamnesis – all this allows you to diagnose violations, and if any, determine which part of the system is damaged – central or peripheral, and establish the cause of the disease.

According to neurologists, the most common cause of damage to the central nervous system is impaired blood circulation (ischemic strokes or bleeding), tumors, various degenerative diseases (Alzhemer, Parkinson’s, etc.).

Brain damage can cause various inflammatory diseases, as well as diseases caused by external factors such as encephalitis, meningitis, as well as autoimmune diseases such as multiple sclerosis.

The cause of primary diseases of the nervous system (migraines, epilepsy, etc.)are poorly functioning nerve cells.

The peripheral nervous system consists of the cranial and spinal nerves and nerve nodes extending from the brain and spinal cord, pressing against the nerves and spreading to the nodes of the nerve nodes and many countless nerve endings located in the tissues. Nerves connect the central nervous system and spinal cord to other parts of the body and organs.

Disorders of the peripheral nervous system can be caused by both external and internal factors, due to which the blood circulation of the nerves, nutrition, and therefore their functions are impaired.The most common causes of disorders of nerves and their functions include viral infections, malnutrition, chronic diseases such as diabetes, metabolic disorders, inflammatory diseases of the blood vessels, atherosclerotic vascular changes.

Neurological pain can also be triggered by inflammatory processes in the body, a lack of vitamins, especially group B, disorders caused by toxins, ranging from exposure to alcohol and ending with heavy metal poisoning.Quite often, nerve damage causes shifts in the spine, bones, muscles, or blood vessels through or near which a peripheral nerve passes. With contact, friction or compression of the nerve by the bony processes of the spine, between the hernias of the intervertebral disc, thickened ligaments, inflammation of the nerve develops. An uncomfortable position of the spine or limbs for a long time, acute injuries can provoke the development of such inflammation.

90,000 Neuroscientists have learned how to restore spinal cord cells inside a living organism

Professional neuroscientists are well aware that the phrase “nerve cells do not regenerate” is just a naive warning against unnecessary stress, which has little to do with scientific facts.In the brain of even an adult, neurogenesis, that is, the formation of new neurons, still occurs. This ability is enough to keep cognitive functions in order, but not, for example, to restore the spinal cord of a driver who injured his spine in a car accident. After such an injury, a “glial” scar appears in the nervous tissue, and the former functions of the spinal cord cannot be fully restored.

The results of the work were published in an article in the prestigious scientific journal Science.

Still, a group of researchers from the Karolinska Institute and St. Petersburg State University, led by the pioneer in brain stem cell research, Professor Jonas Friesen, was able to take a step towards learning how to restore damaged tissues of the central nervous system inside a living organism. The experiments were carried out on mice using transgenic technologies. Scientists have shown that with various spinal cord injuries in mice, it is possible to controllably trigger the formation of full-fledged oligodendrocytes, which will perform their functions of myelination of the axons of the nerve cells of the damaged tissue.It is oligodendrocytes, wrapping their processes around the axons of nerve cells, form the so-called myelin sheaths – a special “insulating material” that promotes the rapid propagation of nerve impulses in the central nervous system (CNS).

Oligodendrocyte formation was derived from ependymal cells that line the central canal of the spinal cord. For this, in these cells, using genetic technologies, they artificially caused the appearance of a special protein, the transcription factor Olig2, which normally controls the program for the formation of specific properties (differentiation) of oligodendrocyte cells in the central nervous system during embryonic development.

Photo: Science magazine

“Unfortunately, the recovery processes in the nervous system are extremely limited,” said Oleg Shuplyakov, one of the authors of the article in Science, head of the synapse biology laboratory at the Institute of Translational Biomedicine, professor at St. Petersburg State University and the Karolinska Institute. “We know that primitive vertebrates, such as salamanders, have such abilities by nature, but not humans.”

Perhaps, thanks to such scientific research in the future, we will be able to completely restore damage to the central nervous system in humans.

Head of the Laboratory of Synapse Biology, Institute of Translational Biomedicine Oleg Shuplyakov

The next steps of the researchers are a detailed study of programs for triggering the differentiation of nerve cells of various modalities in vertebrates, as well as the development of medical technologies that will help restore the functions of the central nervous system after injuries of the central nervous system and in neurodegenerative diseases in humans.

The study was supported by the St. Petersburg State University grant No. 51132811.

Today, scientists from the Institute of Translational Biomedicine of St. Petersburg State University are actively cooperating with colleagues from the Karolinska Institute, one of the largest medical universities in Europe. Within the framework of a cooperation agreement, they conduct joint research, and also develop programs for the training of young specialists.

“A publication in Science is a good example of scientific international collaboration. The ability to work and think together allows for a broader approach to problem solving, a multidisciplinary approach and world-class results that could not be obtained in one laboratory.For several years now, the Institute of Translational Biomedicine, St. Petersburg State University, has been working to find new methods for restoring the functions of the spinal cord and brain, and to develop new methods for reprogramming and differentiating cells. The unique genetic technologies developed within the framework of this work will give a new impetus to these areas and will allow the Institute’s specialists to solve the key problems of modern biomedicine in a new way, ”says the director of the Institute of Translational Biomedicine, St. Petersburg State University, scientific director of the N.I. Pirogov St. Petersburg State University Professor Raul Gainetdinov.

90,000 Central nervous system disorders, CNS diseases


Depending on the cause, there are 4 types of headache: cluster headache, tension pain, pain from low or high blood pressure, migraine. The approach to treatment is different.

Sleep disorders

The duration of a healthy person’s sleep varies from 5-6 to 9-10 hours.But if difficulties with falling asleep or drowsiness interfere with living and working, you need to contact an experienced neurologist or psychotherapist.

Movement coordination disorder

The central nervous system is responsible for dexterity of gait, smoothness of movements, delicate work of the hands. If these functions are impaired, you need to see a neurologist.


Encephalopathy – non-inflammatory diseases of the brain (due to trauma, intoxication, circulatory disorders), which disrupt its main functions.


Stroke is a sharp disturbance of blood flow in the brain, due to which the nerve tissue dies. The success of treatment depends on the speed of seeking help (this must be done in the first few hours), but modern complex therapy with an experienced rehabilitator can restore many functions of the nervous system.

Traumatic brain injury

Head trauma can have serious consequences: regular severe headache, memory impairment, decreased performance, or even epileptic seizures.For diagnosis and treatment, you need to contact an experienced neurologist in a timely manner.

Age-related neurodegenerative disorders

Neurodegenerative changes are age-related, senile changes in the brain that develop faster than expected, interfere with life and work, and therefore require treatment by a neurologist.

Consequences of removal of a brain tumor

Oncological diseases are a serious pathology that is not easy to cope with even in modern medicine. But an experienced neurologist will always be able to alleviate the symptoms and will do everything to make the patient feel better.

Injuries to the central nervous system –

Injuries to the central nervous system

In most cases, which are common in our country, road traffic accidents occur with serious injuries and damage to the central nervous system. In many parts of the world, central nervous system injuries occur in children, adolescents and young people and in most cases are fatal or disabling. Accidents, a large proportion of which are caused by road traffic accidents, as well as falls, physical shock or other types of injury, can lead to serious injury to the brain, spinal cord, as well as their supporting systems and other structures of the body.

Head injuries

Scalped trauma:

If left untreated, a traumatic brain injury to the head can cause bleeding and later lead to shock. Bleeding can usually be controlled with a dressing or clamps attached to the scalp. Cuts, cuts or stab injuries to the head should be closed as soon as possible. In the event of a penetrating fracture of the skull bones, the tears in the scalp tissue must be cleaned and treated in the operating room.Simple cuts on the scalp must be carefully cleaned and treated. If the wound has a small diameter, then closure or joining of its edges is performed. In the case of extensive injuries, the preferred method is the use of a microsurgical technique, thanks to which it is possible to suture the damaged area.

Injured scalp, if it loses its functionality, grafts can be used with which to close the damaged intact layer of the patient’s periosteum.In such cases, the periosteum should be kept moist before the operation. In the absence of blood supply to the outer layer of the bone, its processing will be significantly difficult. Any cuts or scalped injuries should be assessed or supervised by a neurosurgeon.

Skull fractures

Skull fractures are classified into the following types: a fracture without damage to the skin (closed fracture), or in the case of tissue damage (open or compound fracture), a fracture in only one line (linear fracture), a fracture with multiple branches or lines of fractures (stellate fracture) , or a fragmentary (comminuted fracture) and / or fracture, in which the edges of the damaged segment are below the level of healthy bones (depressed) or the usual level (not depressed).

Simple fractures of the skull (linear, stellate or depressed in places) do not require special treatment. However, these damages to the vascular ducts or intracranial sinuses of the dura mater are potentially dangerous. In the event of rupture of such channels, an epidural or subdural hematoma may occur. Simple fractures of the skull in which the sinuses or mastoid processes, being in contact with air, reach the mastoid air cells, such fractures are called “open”.

For compression or depressed fractures, surgery may be required, mainly aimed at removing bone fragments. In the absence of any neurological signs during the operation, the dura mater should be examined and a planned operation to restore it should be performed.

Open skull fractures require surgical intervention. In case of linear or stellate, (not depressed) non-depressor-open fractures, the damaged area should be cleaned and closed after thorough cleaning.In the case of serious injuries to the lower bones with open fractures, a major operation with appropriate treatment should be performed. The dura mater should be examined in the most careful way. To prevent the risk of infection or leakage of cerebrospinal fluid (CSF), a fascia graft should be placed on the affected area. After examining the dura mater and / or brain tissue, it is necessary to prepare and conduct craniotomy, during which the appropriate procedures for an open fracture will be performed.

Bruising (traumatic glasses) or an effect (bat ears) may occur at the base of the fracture. These clinical signs are observed more often with fractures of the anterior cranial and middle cranial fossa. In this type of fracture, isolated cranial nerve lesions located at the exit openings of the cranial nerves can be observed. Depending on the tear or edema, the facial nerve is most often affected in cranial fractures. Most facial nerve lesions heal on their own and do not require any treatment.On the other hand, if the facial nerve is completely damaged, serious surgical intervention is required.

In cases with rhinorrhea or nasal discharge of watery mucous secretions, treatment is necessary. Traumatic CMF discharge usually subsides within the first 7 to 10 days. Such treatment must necessarily be carried out in a neurosurgical clinic.

Penetrating brain injury (crush):

Penetrating herbs of the brain are formed as a result of slowing down, accelerating, rotating, or all of the above actions at the same time in connection with the impact.During the first impact, neural and axonal breaks can form, which represent the primary damage. Complications that develop later, such as intracranial hematoma, cerebral edema, hypoxia, low blood pressure, hydrocephalus, or endocrine disorders, are secondary damage.

Primary brain injury usually does not accompany mild head trauma, and neurological deficits are limited primarily to temporary loss of consciousness (concussion).On the other hand, with moderate to severe injuries, typical reversible or irreversible neurological deficits can be observed. In addition, trauma of this degree is usually accompanied by secondary brain damage.

Shocks that lead to primary damage can be so severe that they can rupture capillaries, superficial subdural veins, or epidural arteries and veins, resulting in a hematoma in the form of internal bleeding. As a result of vasodilation and disruption of the blood-brain barrier, cerebral edema can occur.Ischemia associated with low blood pressure or oxygen deprivation can lead to cell death and cytotoxic edema. Mixing BOS with blood can lead to malabsorption of BOS and hydrocephalus. The release of antidiuretic hormone or diabetes insipidius disrupts the balance of fluids and electrolytes, and cerebral edema may worsen even more. These changes, taken separately or combined, may result in an increase in ICP.

After a high ICP of cerebral perfusion pressure (CPP) decreases, secondary brain injury may occur.Increased intercranial pressure is one of the most important factors affecting the prognosis of head injuries. Therefore, aggressive treatment must be performed to prevent secondary brain damage when cerebral perfusion pressure drops. If possible, early intervention should be performed at the scene of the accident by monitoring the airways and using hyperventilation.

Ambulance is the basis for the assessment of a victim’s condition. Despite the complexity of the overall neurological assessment of patients who do not respond and do not cooperate, some characteristics of patients are critically important.

Patients who do not have headache, lethargy, or focal neurological deficits are less likely to develop a secondary complication as a result of a head injury. Imaging screening techniques are generally not performed for asemptomatic patients. In this case, in patients with or without focal neurological deficit, but who also have severity of symptoms, computed tomography (CT) should be performed.

Spinal cord injury

Traumatic injuries of the spinal cord, spinal fractures, dislocations with fractures, hyperextension in canals that were narrowed earlier can be observed during intervertebral hernia of disc material into the canal, with gunshot wounds or stab wounds.Neurological deficits can be mild and temporary, or they can be severe and permanent. With or without coma, any head injury or multitrauma should always be suspected of having a fracture or injury to the spine or spinal cord. If at first it is assumed that the spine is unstable, the patient should be placed on a flat surface until a detailed examination and diagnosis is carried out, in this case, a rigid stretcher with a neck fixation is best suited.

Clinical reports for injuries of the spine or spinal cord: sensitivity of the spine, loss of strength in the limbs, convulsions or paresthesia, respiratory failure and low blood pressure. If we are talking about the clamping of the nerve spinal endings, then in the corresponding myotome and dermatome, the loss of movement and sensitivity manifests itself in the form of a characteristic radiculopathy. When it comes to pinching the spinal cord, various symptoms associated with developing myelopathy may appear

Complete tissue damage is expressed as a complete loss of movement and sensitivity below the level of functional damage, this is a manifestation of a complete anatomical or physiological section.Areflexia, flaxity, loss of sensation, and autonomic paralysis appear below the level of damage to acute incisions. For all cuts above T5, there is a constant decrease in blood pressure, which develops in connection with the loss of sympathetic vascular tone.

Incomplete spinal cord injuries below the level of trauma, together with loss of ipsilateral motor function and coordination / vibration sensitivity, as well as loss of pain and temperature sensitivity, may result in Brown Séquard’s syndrome.Anatomically, this is due to the complete transverse lesion of the spinal cord. Central spinal cord syndrome is characterized mainly by paresis of the hands, weakness in the legs is less pronounced, there are varying degrees of severity of sensitivity disorders below the level of the lesion, urinary retention. In some cases, mainly with trauma, accompanied by a sharp bending of the spine, a syndrome of damage to the posterior cords of the spinal cord may develop – loss of deep types of sensitivity.

Damage to the spinal cord (especially with complete damage to its diameter) is characterized by dysregulation of the functions of various internal organs: respiratory disorders in cervical lesions, intestinal paresis, dysfunction of the pelvic organs, trophic disorders with the rapid development of pressure ulcers.

In the acute stage of trauma, cardiovascular disorders and a drop in blood pressure are often observed. With a fracture of the vertebrae, an external examination of the patient and the identification of such changes as concomitant damage to soft tissues, reflex muscle tension, sharp pain when pressing on the vertebrae, and finally, external deformity of the spine can have a certain value in its recognition.

Along with this, there may be obstruction of gastric distention, the treatment of which usually requires nasogastric drainage. Likewise, bladder distention occurs, which occurs due to compression of the muscles in the bladder and pelvic floor. Emptying the bladder negatively affects venous circulation and can lead to increased systemic hypotension of the inferior vena cava or by putting severe pressure on the pelvic veins to prevent excessive bloating.

If the spinal cord injury is above the T5 level, the blood pressure is usually low.At the same time, denervation of the sympathetic nervous system is formed, which causes an increase in clogging of the veins and a weakening of venous circulation.

Tachycardia is a compensatory response to hypotension and is common in cervical spinal cord injury and bradycardia. If patients do not have symptoms of myocardial infarction or are at risk of stroke or paralysis due to other serious illnesses, this type of bradycardia does not need treatment.

After hemodynamic fixation is provided, it is necessary to perform an X-ray of the patient’s spine, who must stand motionless on a special board fixing the spine with a rigid cervical collar fixed.Make sure that the fixation is firm to ensure the accuracy of the resulting images. If the patient has multiple injuries and / or is in a coma, it is necessary to obtain clear images of his spine, which will fully display all segments of the spine. For a more detailed examination of the fracture sites, CT can be performed, as well as axial and sagittal images. If there are no abnormalities on radiographs and, at the same time, if there is a neurological deficit in the background of the spinal cord, then to identify damage to the intervertebral discs or spinal epidural hematoma after CT, the patient can be examined using MRI or myelography.

Treatment is aimed at correcting the structure of the spine, protecting intact nerve tissue, restoring nerve tissue and ensuring long-term stabilization of the spine. In this case, priority is given to the correction and fixation of the displaced vertebrae or the elimination of any fractures or injuries to the segments of the spine.

Displacements of the vertebrae can almost always be corrected in a neutral position using skeletal traction. In order to make sure that the vertebrae are aligned correctly, X-rays are often taken.

In patients with fractures of the lumbar spine, treatment begins primarily with fixation. At the same time, the fixation is not so tight compared to cervical fractures. Avoiding bending, stretching, rotation, the patient should lie motionless on a flat bed. As a rule, there are far fewer systemic complications associated with neurological disorders, and nevertheless, vigilance is necessary to ensure neurological recovery.

Indications for the need for early surgery in patients with spinal cord injury are: fractures / displacement that cannot be cured with closed surgical methods, neurological disorders in patients with local lesions; Penetrating injuries that cause or do not leak CMF or place severe pressure on the spinal cord, or damage channels imaged by MRI or myelography.For open wounds, such as stab wounds and gunshot injuries, although the spine is completely damaged, it is necessary to very thoroughly rinse and clean and close the site of injury. them or bruises. ny places even. whether or not the wounds are cleaned and sealed. The reasons for early surgery to stabilize the spine are justified. Because it provides an opportunity for early mobilization and rehabilitation of the patient. Depending on the nature and degree of spinal injury, arthroscopic or a posteriori methods can be used.

If recovery with closed methods has yielded successful results and fixation of the fracture site has been ensured, then complete recovery may require at least 3 months of using stable external immobilization.

Stable external immobilization is also required for surgical intervention during recovery and / or in cases of urgent need for its use. After the application of arthroscopic or posterior plates, the use of a cervical collar is sufficient.When fixing the lumbar spine, again, it is necessary to ensure the immobility of the spine for at least 3 months using a plastic jacket or a plastic-plaster fixator. Plain radiographs throughout the spinal cord repair process will be examined to monitor the spine.

If any functions of the spinal cord are preserved immediately after the injury, then some functions may be restored provided that there is no secondary damage to the spinal cord and spinal cord.In cases with the occurrence of bone marrow injuries, the functions located below the level of the lesion can be completely restored. Rehabilitation of such patients is carried out in accordance with their daily care and professional adaptation. Long-term skin care problems and recurrent urinary tract infections are the cause of premature death.

90,000 Effect of nicotine on the central nervous system

The human intellect suffers from nicotine, for many without a cigarette mental tasks become beyond their power, memory decreases, logical thinking weakens.Acting on the central nervous system as a drug, nicotine makes a person completely addicted to a bad habit.

The human nervous system is a complex structure that ensures the correct functioning of the whole organism. Its main function is to receive and process information coming from the outside world and from within the body, transmit information about the state of the body to the brain, coordinate voluntary body movements, regulate its involuntary functions – breathing, digestion, heartbeat, maintaining body temperature and others.Considering all this, one can imagine how strongly nicotine and smoking affect the human nervous system.

Anatomically, the human nervous system is divided into the central and peripheral nervous systems – the CNS and PNS. The central nervous system is a tandem of the brain and spinal cord. The nerve centers contained in the cerebral hemispheres constitute the intellectual basis of a person, provide his personality, consciousness, understanding. PNS provides a mutual connection of the central nervous system with all organs and systems of the body.

The involuntary functions of the body are controlled by the autonomic (autonomic) nervous system; its structures are located both in the central nervous system and in the PNS.

Nicotine and the nervous system

Nicotine is a neurotoxic poison that disrupts the harmonious flow of electrochemical processes in the nervous system and causes the death of neurons. When tobacco addiction occurs, the body becomes addicted to nicotine.

Initially, nicotine has an exciting effect on the nervous system, but soon this effect is replaced by oppression due to vasoconstriction.In the process of smoking, nicotine becomes a kind of stimulant for the brain, accelerating the conduction of nerve impulses, but then the brain processes are greatly inhibited, the brain’s need for rest is triggered. As you get used to it, the brain itself begins to demand a “dose”, not wanting to work on its own, without doping. If it is impossible to smoke, a person has anxiety, severe irritability, lack of attentiveness and concentration.

People who smoke are more prone to fatigue of the nervous system and neurasthenia.A vicious circle is formed: the smoker who works hard starts smoking more and more often in order to spur the body, and gets even more overworked. Such people can observe in themselves a memory disorder, sleep disturbance, headache, frequent mood swings, decreased performance. Neuritis, sciatica, polyneuritis – these diseases of the PNS are also common among “hard-core” smokers.

Smoking has a detrimental effect on the autonomic nervous system, worsening the work of internal organs – the activity of the cardiovascular system is upset, the functioning of the digestive system is disrupted.

The senses also receive their “portion” of nicotine influence. With prolonged excessive smoking, disturbances such as decreased visual acuity, impaired hearing, taste, and smell are possible.

However, according to the latest research conducted in the United States, it has been proven that nicotine stimulates cognitive abilities. Also, do not confuse the harm of smoking and the effect of pure nicotine.

From the effects of nicotine, the intellectual activity of a person suffers, many without a cigarette become unable to do mental tasks, memory decreases, logical thinking weakens.Acting on the central nervous system as a drug, nicotine makes a person weak-willed, completely dependent on a bad habit.

How to protect the nervous system from the effects of nicotine

It is necessary to move a lot, muscle activity has a beneficial effect on both the work of the brain and the conduction in the nerve fibers, in addition, improved blood circulation will have a positive effect on the nervous system.

Intellectual activity involves all components of the nervous system, so do crossword puzzles, read more, compose handwritten texts.

Eat properly so that the body receives all the necessary minerals and trace elements. And, of course, quit smoking. Remember that the correct functioning of the body, and, accordingly, a high-quality and full-fledged life is impossible if the nervous system is disrupted.

90,000 Minor injuries of the central nervous system

A cerebral stroke is a disease that is caused by a blockage of a blood vessel (acute ischemic stroke in 75-80% of patients) or when a blood vessel bursts and hemorrhage occurs in or around the brain (acute hemorrhagic stroke in 20-25% of patients).

In our country, stroke is the leading cause of death among women, and the second among men. In addition to the fact that it is a disease with a very high mortality rate (in the first month of the disease it reaches 23% of patients), it is also a neurological disease with the highest level of disability and with a high recurrence rate (every third patient recurs again within five years stroke).

Stroke risk factors that can be affected: high blood pressure, diabetes, heart disease, abnormal blood fat levels, obesity, smoking, sedentary lifestyle, poor diet, alcohol abuse.

Symptoms suggestive of a cerebral stroke: sudden weakness, paralysis and / or numbness in one side of the body (face, arms, legs), sudden confusion with speech impairment, sudden vision problems, sudden difficulty walking, dizziness, loss of balance, sudden headache that is usually accompanied by nausea

Every patient with a cerebral stroke must be urgently taken to the nearest specialized institution.

Early rehabilitation of such patients is used from the very onset of the disease to prevent complications in other body systems (pneumonia, deep vein thrombosis, pulmonary embolism, bedsores, joint stiffness).After a month of rehabilitation, it continues in a specialized rehabilitation center.

Immediate goals of rehabilitation:

  • Teach the patient to walk again. By yourself or with the help of some kind of device
  • Teach the patient to use the upper limb (arm) to maximum use in daily activities
  • Teach the patient himself to perform actions that are necessary for daily life (eating, washing, bathing, shaving, dressing)

The rehabilitation program is adjusted individually for each patient.The physiotherapy treatments we use are kinesitherapy (exercises), functional occupational therapy, manual or underwater massage, hand and foot baths, paraffin wax, electrotherapy and magnetotherapy.

The treatment lasts, depending on the functional state of the patient, from one to three months. In the first year of rehabilitation, the success of recovery is greatest.

Stroke tends to recur and secondary prevention is therefore of great importance (controlling high blood pressure, cholesterol and blood sugar levels, taking prescribed medication regularly, seeing a doctor regularly to monitor the condition, quitting bad habits – smoking, unhealthy eating) , alcohol consumption).

90,000 How can coronavirus affect the brain? | World Events – Estimates and Forecasts from Germany and Europe | DW

Recently, there has been numerous evidence that the new coronavirus SARS-CoV-2 is actively attacking not only the lungs and respiratory tract, but also other organs of the human body. Serious damage can also be done to the heart, blood vessels, nerve tissues, and skin.

British neurologists published shocking data in the journal Brain that the coronavirus can cause serious brain damage, even in patients with mild symptoms of COVID-19 or in those who have already recovered.

Neurologists at University College London have diagnosed acute disseminated encephalomyelitis in over 40 UK patients with COVID-19. This inflammatory disease leads to degenerative destruction of the central nervous system, which affects the so-called myelin sheath of nerve cells in the brain and spinal cord.

Various consequences of COVID-19 disease

Twelve of these patients suffered from inflammation of the central nervous system, ten from transient encephalopathy (brain disease.- Ed. ) with delusions or psychosis, eight had a stroke, another eight had nerve damage, mostly with Guillain-Barré syndrome. It is an autoimmune reaction that attacks nerve cells, causes paralysis, and is fatal in 5 percent of cases. Due to such complications, one of the patients died at the age of 59 years.

“COVID-19 attacks the brain in a way we’ve never seen in any virus before,” said Michael Zandi, lead author of the study and consultant at University College London.Serious brain damage is uncommon, even in patients with mild symptoms.

COVID-19 patients in Brazil

New clinical studies of diseases caused by the coronavirus confirm fears that COVID-19 may cause long-term health problems in some patients. Many patients feel short of breath and fatigue long after they recover. Others who have recovered suffer from limb numbness, weakness, and memory problems.

“From the point of view of biology, acute multiple encephalomyelitis is similar to multiple sclerosis, but it is more severe.Some patients develop long-term health problems, while others recover well, “Zandi noted.

The scale of complications remains to be determined

not even identified, because many patients are in hospitals in too bad shape to do brain examinations or other procedures.

“We would like to draw the attention of doctors around the world to these complications from coronavirus,” Zandi said.According to him, patients with cognitive impairments, memory problems, fatigue, deafness or weakness should definitely consult a neurologist.

Shocking examples from practice

Disturbing isolated cases from practice were also published. For example, a 47-year-old woman, after a week of coughing and high fever, suddenly developed a headache and numbness in her right arm. In the hospital, she became sleepy and did not react to anything. During an emergency operation, she came to remove part of her skull to relieve pressure due to cerebral edema.

A 55-year-old patient, who had not previously suffered from mental illness, began to behave strangely on the day of discharge from the hospital. She put on and took off her coat over and over again, then she began to hallucinate, at home she saw monkeys and lions. She was prescribed antipsychotic medication at the hospital.

Thousands of cases of brain damage in “Spanish flu”

British neurologists fear that in some patients COVID-19 may leave such brain damage that will become noticeable only in the following years.According to the study, patients also had similar complications after the devastating Spanish flu of 1918-1920. Probably nearly a million people also had complications in the form of brain damage.

“Of course, we hope that this will not happen. But since we are faced with a pandemic of this magnitude, which will affect a large part of the population, we must be prepared,” said Michael Zandi.

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