What are the main components of the central nervous system. How does the brain process sensory information. What role does the spinal cord play in reflexes. How do the forebrain, midbrain, and hindbrain work together.

The Central Nervous System: An Overview

The central nervous system (CNS) is a crucial part of the body’s overall nervous system, working in tandem with the peripheral nervous system to control bodily functions and process information. Comprised of the brain, cerebellum, and spinal cord, the CNS is responsible for integrating sensory input, coordinating body functions, and facilitating complex cognitive processes.

Understanding the structure and function of the CNS is essential for grasping how our bodies operate on a fundamental level. Let’s explore the four main parts of the central nervous system and their unique roles.

The Brain: Command Center of the Body

As the most complex organ in the human body, the brain serves as the command center for all bodily functions. It processes sensory information, controls voluntary movements, regulates involuntary functions, and enables higher-order thinking.

Three Major Regions of the Brain

1. Forebrain
2. Midbrain
3. Hindbrain

Each of these regions plays a distinct role in managing various aspects of our physical and cognitive functions.

The Forebrain: Center of Complex Cognition

The forebrain is responsible for processing information required for complex cognitive tasks. Its functions include:

• Sensory processing
• Voluntary motor control
• Speech production
• Critical thinking
• Homeostasis regulation

How does the forebrain maintain homeostasis? It regulates body temperature, blood pressure, and hormone production, as well as managing sensations like pleasure, pain, hunger, and thirst.

The Midbrain: Bridging Communication

Serving as a crucial connector between the forebrain and hindbrain, the midbrain also links the brain to the spinal cord. Its primary functions include:

• Processing auditory and visual information
• Controlling eye movement

The Hindbrain: Regulator of Vital Functions

The hindbrain plays a critical role in maintaining essential bodily functions. It is responsible for:

• Muscular movement coordination
• Respiratory rhythm regulation
• Heart rate and blood pressure control
• Sleep-wake cycle management
• Controlling involuntary reflexes (e.g., sneezing, swallowing)

The Cerebellum: Fine-Tuning Motor Control

While often considered part of the hindbrain, the cerebellum deserves special attention due to its crucial role in motor control and coordination. How does the cerebellum contribute to our movements? It fine-tunes motor activities, ensuring smooth and precise execution of voluntary movements. Additionally, the cerebellum plays a role in balance, posture, and motor learning.

The Spinal Cord: Information Highway and Reflex Center

The spinal cord serves as a vital communication link between the brain and the rest of the body. Its functions include:

• Transmitting signals between the brain and peripheral nervous system
• Processing and integrating sensory information
• Controlling simple reflexes independently of the brain

How can the spinal cord control reflexes without brain input? It contains neural circuits capable of processing sensory information and generating motor responses rapidly, bypassing the need for brain involvement in certain reflexive actions.

Neurotransmission: The Language of the CNS

The central nervous system communicates through a complex network of neurons using electrical and chemical signals. Neurotransmitters play a crucial role in this process, facilitating the transmission of information across synapses.

Key Neurotransmitters in the CNS

• Glutamate: The primary excitatory neurotransmitter
• GABA: The main inhibitory neurotransmitter
• Dopamine: Involved in reward and motivation
• Serotonin: Regulates mood and sleep
• Norepinephrine: Affects alertness and arousal

How do these neurotransmitters influence our behavior and mental states? By binding to specific receptors on neurons, they can either excite or inhibit neural activity, modulating various cognitive and physiological processes.

Protecting the CNS: Barriers and Support Systems

The central nervous system is protected by several layers of defense, ensuring its optimal functioning and safeguarding it from potential harm.

The Blood-Brain Barrier

This selective membrane prevents many substances in the bloodstream from entering the brain tissue. Why is the blood-brain barrier crucial for CNS health? It protects the brain from potentially harmful substances while allowing essential nutrients to pass through.

Cerebrospinal Fluid (CSF)

CSF surrounds the brain and spinal cord, providing cushioning and protection. It also aids in the removal of waste products and helps maintain proper chemical balance in the CNS.

Meninges

These protective membranes envelop the brain and spinal cord, offering an additional layer of defense against physical injury and infection.

CNS Disorders: When the Command Center Falters

Disorders of the central nervous system can have profound effects on a person’s cognitive abilities, motor functions, and overall quality of life. Some common CNS disorders include:

• Alzheimer’s disease
• Parkinson’s disease
• Multiple sclerosis
• Epilepsy
• Stroke
• Brain tumors

What causes CNS disorders? The etiology of these conditions can vary widely, ranging from genetic factors and environmental influences to traumatic injuries and infections. Understanding the underlying mechanisms of these disorders is crucial for developing effective treatments and preventive strategies.

Emerging Therapies for CNS Disorders

Research in neuroscience continues to uncover new potential treatments for CNS disorders. Some promising areas of study include:

• Gene therapy
• Stem cell transplantation
• Neurofeedback techniques
• Brain-computer interfaces
• Targeted drug delivery systems

How might these emerging therapies revolutionize the treatment of CNS disorders? By addressing the root causes of these conditions and providing more precise and personalized interventions, these approaches hold the potential to significantly improve patient outcomes and quality of life.

The CNS and Neuroplasticity: Adapting to Change

One of the most fascinating aspects of the central nervous system is its ability to adapt and reorganize itself throughout life. This phenomenon, known as neuroplasticity, allows the brain to form new neural connections and modify existing ones in response to experiences, learning, and even injury.

Types of Neuroplasticity

• Structural plasticity: Changes in the physical structure of neurons
• Functional plasticity: Alterations in the strength of synaptic connections
• Synaptic plasticity: Modifications in the efficiency of synaptic transmission

How does neuroplasticity benefit the CNS? It enables the brain to adapt to new situations, recover from injuries, and optimize cognitive functions throughout life. This remarkable ability has significant implications for rehabilitation following brain injuries and the development of cognitive enhancement strategies.

Harnessing Neuroplasticity

Understanding and leveraging neuroplasticity can lead to improved treatments for various neurological conditions and cognitive enhancement techniques. Some strategies that capitalize on neuroplasticity include:

• Cognitive training exercises
• Physical therapy for stroke recovery
• Mindfulness meditation practices
• Brain-stimulation techniques

By engaging in activities that promote neuroplasticity, individuals may be able to enhance their cognitive abilities, recover more effectively from brain injuries, and maintain better overall brain health throughout their lives.

The CNS and Consciousness: Unraveling the Mystery

One of the most profound and elusive aspects of the central nervous system is its role in generating consciousness. Despite significant advances in neuroscience, the precise mechanisms underlying conscious experience remain a subject of intense study and debate.

Theories of Consciousness

Several theories attempt to explain how the CNS gives rise to conscious awareness:

• Global Workspace Theory
• Integrated Information Theory
• Higher-Order Thought Theory
• Quantum Consciousness Theory

What do these theories propose about the nature of consciousness? While they differ in their specific mechanisms, most agree that consciousness emerges from the complex interactions of neural networks within the CNS, particularly in the cortical regions of the brain.

Neural Correlates of Consciousness

Researchers have identified several brain areas and processes that appear to be closely associated with conscious experience:

• Thalamo-cortical system
• Prefrontal cortex
• Posterior cingulate cortex
• Claustrum

How do these neural correlates contribute to conscious awareness? They are thought to play crucial roles in integrating sensory information, maintaining attention, and generating the subjective experience of consciousness.

The Future of CNS Research: Expanding Our Understanding

As technology advances and our knowledge of the central nervous system grows, new frontiers in neuroscience research continue to emerge. Some exciting areas of ongoing and future study include:

Connectomics

This field aims to map the complete neural connections within the brain, creating a comprehensive wiring diagram of the CNS. How might connectomics revolutionize our understanding of brain function? By providing a detailed map of neural connections, it could offer unprecedented insights into how information flows through the brain and how different regions interact.

Optogenetics

This innovative technique allows researchers to control specific neurons using light. What potential applications does optogenetics have in CNS research? It could enable more precise studies of neural circuits, potentially leading to new treatments for neurological disorders and a deeper understanding of brain function.

Artificial Intelligence and Machine Learning

The integration of AI and machine learning techniques with neuroscience is opening new avenues for analyzing complex brain data and modeling neural processes. How might AI contribute to our understanding of the CNS? By processing vast amounts of neurological data and identifying patterns that may not be apparent to human researchers, AI could accelerate discoveries in brain function and disease mechanisms.

Brain-Computer Interfaces

Advancements in brain-computer interface technology are bridging the gap between the CNS and external devices. What potential applications do brain-computer interfaces have? They could enable more effective prosthetics for individuals with paralysis, provide new communication methods for those with severe motor disabilities, and even enhance cognitive abilities in healthy individuals.

As research in these and other areas progresses, our understanding of the central nervous system will continue to expand, potentially leading to groundbreaking treatments for neurological disorders and new insights into the nature of cognition and consciousness.

What Do the Different Parts of The Nervous System Do?

Posted on August 17, 2020 Neurology

The body’s nervous system is made up of two major parts, the central nervous system, and the peripheral nervous system. These two parts of the nervous system act jointly to assure your body is communicating all of its sensory information and needs. The central nervous system and the peripheral nervous system each play different roles in controlling your body’s functions.

Central Nervous System

The central nervous system (CNS) is made up of the brain, cerebellum  and the spinal cord

The Spinal Cord

The spinal cord directs signals from the brain to the body and is capable of controlling simple reflexes without transmitting information from the brain. 

The Brain

The brain processes most of the body’s sensory information and is responsible for coordinating conscious and unconscious body functions including feeling, thinking, and maintaining homeostasis, which is the body’s ability to maintain a stable environment. The brain is made up of three regions, the forebrain, the midbrain, and the hindbrain. 

• The Forebrain: The forebrain works to process the information needed to complete complex cognitive tasks. The parts of the forebrain are responsible for sensory functions, voluntary motor skills, speech, and critical thinking. It also controls homeostasis which is maintained through regulation of body temperature, blood pressure, pleasure, pain, hunger, and thirst as well as hormone production. 
• The Midbrain: The midbrain connects the forebrain and the hindbrain and carries the important job of connecting the brain to the spinal cord. It processes sounds and sights and works to control the movement of the eye.
• The Hindbrain: The hindbrain is responsible for muscular movement, respiratory rhythm, heart rate, blood pressure, sleep, and staying alert while awake. Involuntary reflexes like sneezing and swallowing are also controlled by the parts of the hindbrain.

Peripheral Nervous System

Nerves make up the peripheral nervous system (PNS), which works to send signals to and from the CNS, the body’s organs, muscles, and senses. The PNS is broken into the somatic nervous system and the autonomic nervous system.

Somatic Nervous System

The somatic nervous system is made up of motor neurons and sensory neurons that help the body perform voluntary activities. 

Autonomic Nervous System

The autonomic nervous system is made of neurons that work to connect the CNS with the body’s internal organs. It is divided into two parts, the sympathetic nervous system, and the parasympathetic nervous system.

Sympathetic Nervous System

The sympathetic nervous system stimulates what is known as the fight or flight response in the body. It prepares the body’s energy for stressful or energy-exerting activities.

Parasympathetic Nervous System

The parasympathetic nervous system, on the other hand, works to conserve energy. It signals the body to conserve its energy while it sleeps and relaxes.

See a Neurologist

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We do ask that patients experiencing symptoms like fever, cough, or shortness of breath reschedule your appointment or schedule a telemedicine appointment. Please contact our office to change your in-person visit to a Telehealth visit (718) 515-4347. We thank you for your understanding and cooperation. 

Central Nervous System: Definition, Function, Parts

Definition

The central nervous system (CNS) consists of the brain and spinal cord. This body system is responsible for integrating and coordinating the activities of the entire body. Through these physical structures, thought, emotion, and sensation are experienced, and body movements are coordinated.

Overview

The central nervous system can be thought of as the coordination and integration system within organisms. The CNS takes signals from the peripheral nervous system, processes them, then creates new signals to coordinate actions of different body systems. For instance, long-term and short-term metabolism and homeostasis are regulated through close interaction between the central nervous system and the endocrine system.

While the CNS is functionally made of neurons, other cell types such as glial cells play important supporting roles. Some cranial nerves, like the optic and olfactory nerves, are also considered to be a part of the central nervous system. All other nerves are part of the peripheral nervous system, but they still connect to the CNS. As such, the central nervous system is the coordinated processing center of the body.

Central Nervous System Diagram

Central Nervous System Function

Coordination and Movement

The primary function of the central nervous system is integration and coordination. The CNS receives input from a variety of different sources, and implements an appropriate response to the stimuli, in a cohesive manner. For instance, in order to walk the CNS needs visual and integumentary cues – the texture of the surface, its incline, the presence of obstacles, and so forth.

Based on these stimuli, the CNS alters skeletal muscle contraction. Once infants learn to walk, this happens involuntarily, no longer requiring conscious thought or concentration. A similar process of receiving complex stimuli and generating a coordinated response is required for vastly varied activities – whether it is balancing a bicycle, maintaining a conversation or mounting an immune response.

Thought and Processing

The CNS, especially the brain, is considered the physical seat for most higher-order mental functions. Neuronal connections form the basis for thought and retention of memory. The brain plays an important role in the development of speech, language, and communication. These tasks involve an association of abstract symbols and sounds with concrete objects and emotions. Motivation, ambition, reward, and satisfaction are also mediated through neuronal connections in the CNS.

At the same time, the limbic system of the brain also controls the most basic emotions and drives, such as pleasure, fear, anger, hunger, thirst, sleepiness and sexual desire. In addition, involuntary reflexes are mediated by the spinal cord, providing protection and quickly preventing injury.

The CNS directly or indirectly influences nearly every internal organ system, whether related to respiration, digestion, excretion, circulation or reproduction.

Central Nervous System Parts

In vertebrates, the brain and spinal cord are encased in bony cavities, with the brain residing within the skull, and the vertebral column protecting the spinal cord. Three membranous coverings, called the meninges, provide mechanical support and protection to the central nervous system. These meninges are called pia mater, arachnoid mater and dura mater. Pia mater is the layer closest to the nervous tissue and dura mater lies next to the bone.

Additionally, cerebrospinal fluid (CSF), produced in the four ventricular cavities of the brain, flows between the pia mater and arachnoid mater, providing protection from pathogens and mechanical support to the entire central nervous system. Special glial cells called ependymal cells produce CSF.

The Brain

The brain is made of the cerebrum, cerebellum, and brain stem. The cerebrum consists of two large hemispheres demarcated by a thick band of nerve fibers called the corpus callosum. Each of the hemispheres can be divided into four lobes. These are named the frontal, parietal, temporal and occipital lobes.

Each of these lobes is relatively distinct in function, relating to higher levels of cognition (frontal lobe), somatosensory input (parietal lobe), auditory stimuli (temporal lobe), or visual stimuli (occipital lobe). The localization of function to different lobes was initially discovered in patients with brain damage. Further study has indicated a high level of plasticity as well as communication and integration between neurons in different lobes.

The Cerebrum

The outer layer of the cerebrum is called the cerebral cortex and this is usually pinkish grey in color and contains neural cell bodies. It can be divided on the basis of function into sensory, motor and association areas as shown in the image below. For instance, the primary sensory cortex receives sensory input from the body as well as from specialized sense organs. The motor areas are involved in the control and execution of voluntary motor activities. Association areas are necessary for perception, abstract thinking, and associating new sensory input with memory.

Brain Motor and Sensory of the Cerebral Cortex

These demarcations of the cerebral cortex are usually represented bilaterally in both hemispheres as seen in the image below.

Brain Sensory Motor

The Cerebellum

The cerebellum is smaller than the cerebrum, is made of two lobes, and is located behind the brain stem. It is involved in the coordination of different muscle groups to produce smooth movement, controlling posture and balance. The neurons of the inner ear associated with balance relay their information to the cerebellum, which also receives auditory and visual input.

The Brainstem

The brainstem is made of three parts – the midbrain, pons, and the medulla oblongata. The medulla controls most involuntary actions, while the midbrain and pons are associated with sensory functions, excitation, and motivation. The brain stem connects the brain with the spinal cord.

The Spinal Cord

The spinal cord is about 17 inches in length, tapering along the length of the vertebral column in humans, beginning near the occipital bone and ending at the lumbar region of the spine. It connects the brain with most parts of the body while also containing independent neural networks for pattern generation and for executing reflexes.

It can be divided into 31 segments, each giving rise to a pair of spinal nerves. Spinal nerves carry both sensory and motor signals between the body and the spinal cord. The central part of the spinal cord consists of an H-shaped grey column containing the cell bodies of spinal cord neurons. The myelinated axons of these neurons form the white matter.

Example of Central Nervous System Activity

The key to the work of the CNS is integration. It receives input from various sources and creates a cohesive response. This is particularly important for animals in complex social structures, like human beings. For instance, meeting an old friend and catching up over coffee can seem like a relaxing event. However, to facilitate a successful interaction, the CNS needs to be abuzz with activity.

It begins when you see the friend and recognize her – your brain is correlating the neurochemical signals received from the optic nerve with the image you have in memory. It proceeds with the recollection of common experiences and the slipping into the vernacular of an earlier time.

Some research suggests that the CNS can even associate different body language with different sets of people or events. You may find yourself using phrases that haven’t been in your vocabulary for years or changing your accent and posture slightly, without being actively aware of it. The CNS retrieves a memory and correlates the memory with your current situation to generate an emotional and physiological response.

Central Nervous System Disease

Infection

The CNS can be attacked by pathogens – bacteria (bacterial meningitis), viruses (viral encephalitis), fungi (fungal meningitis, abscesses) or parasites (toxoplasmosis, cysticercosis). Alternatively, the CNS could be a secondary site for infection in advanced stages of illness from a different organ, as in tuberculosis or syphilis. The meninges covering the central nervous system are particularly susceptible to infection, especially when head trauma allows pathogens from other organs access to these delicate tissues, through the cerebrospinal fluid.

Lack of Blood Flow

The CNS is also particularly susceptible to changes in the vascular networks supplying critical nutrients, glucose, and oxygen. Blocks in blood vessels or burst capillaries can lead to strokes due to neuronal cell death. Depending on the location of the injury and the kind of medical attention received, the individual could suffer either loss of sensory, motor, cognitive or associative functions. Some people lose language abilities (aphasia), some lose memories while others may lose the full range of voluntary movements (paralysis).

Neurodegenerative Diseases

Ailments that lead to the accumulation of debris or unfolded proteins within cells of the body are particularly debilitating for the nervous system. Ailments like Alzheimer’s and Parkinson’s disease are progressive neurodegenerative disorders. The symptoms become more debilitating with age, and while there is a clear genetic factor involved in some of these ailments (Huntington’s disease) in most other neurodegenerative diseases, both genetic and environmental factors seem to be involved.

The cause for Alzheimer’s disease is still not known, though autopsies of patients who have suffered from the ailment often reveal protein plaques in the brain. There could be the involvement of neurotransmitter deficiency, aggregates of specific proteins, changes to the vascular structure of the brain, enlargement of brain ventricles and a shrinking of active tissue in the cerebral cortex.

Parkinson’s disease involves a progressive loss of motor ability, beginning from fine motor skills, and changes to posture and balance. Over time, all deliberate movements become difficult. The primary region of the brain affected by the disease is the substantia nigra, a region in the midbrain. As in Alzheimer’s, the definitive cause of Parkinson’s disease is not known.

Cancer

The CNS could also be affected by tumors and cancerous growths. The symptoms would depend on the location of the growth, size, malignancy, and the site of origin. Therefore they could lead to headaches, loss in cognitive ability, hearing loss, changes to motor control and autonomic functions. Tumorous growths could arise from different factors – exposure to ionizing radiation, carcinogenic environmental pollutants, retroviral infections, inherited genetic mutations or they could be idiopathic in origin, with no obvious causative agents.

Alcoholism and Addiction

Addiction is a disease of the brain in which the patterns of normal brain function are disrupted by the use of drugs or alcohol. For instance, a stimulant such as cocaine will increase blood flow and neurotransmitter release in the brain, giving it an exaggerated sense of wellbeing. Over time, the brain will become conditioned to expect these massive releases, and without the cocaine, the brain and body will experience withdrawals.

Alcohol is a depressant, meaning it slows body systems such as heart rate and breathing. Like any drug, alcohol changes the way the brain functions. Long-term alcoholics can have violent withdrawal symptoms because their brain and body have become accustomed to being severely depressed. Other depressants, such as heroin, create similar actions and also lead to severe addiction.

Quiz

1. Which of these statements about the CNS is NOT true?

A.The CNS is made of the brain, spinal cord, and cranial nerves

B.The CNS is protected by skeletal structures, three meningeal membranes, and CSF

C.The cerebellum receives auditory and visual stimuli to coordinate autonomic functions

D.None of the above

2. Why do diseases involving abnormally folded proteins preferentially attack the nervous system?

A.There are more proteins in neurons

B.Neurons do not have the capacity to rectify misfolded proteins

C.Neurons have a limited capacity for regeneration

D.All of the Above

3. Which of these pathogen:disease pairs is correct?

A.Fungi: Toxoplasmosis

B.Bacteria: Meningitis

C.Viruses: Cysticercosis

D.All of the above

4. What are the main components of the central nervous system?

A.The brain

B.The spinal cord

C.All of the above

D.None of the Above

5. If your spinal cord is damaged, why might you lose the ability to move your limbs?

A.The spinal cord carries nerve signals from the brain, to the body, and back again.

B.This does not happen when your spinal cord is damaged.

C.You need your spinal cord to send hormonal signals to your arms and legs.

Diseases of the central and peripheral nervous system

Version for the visually impaired

Treatment of diseases of the respiratory system, ENT diseases, circulatory organs, PNS, metabolic disorders, diseases of the eye and its adnexa

Sanatorium treatment after Сovid-19

Asthma school (training in special breathing techniques for bronchial asthma)

Pump-room on the territory of the sanatorium0003

The human nervous system is anatomically divided into two parts: central (CNS) and peripheral (PNS). It is a complex structure that permeates all organs and tissues of our body. It is thanks to it that self-regulation of all vital functions of the body is possible, as well as the perception, storage and processing of the information received. Nerve impulses allow us to feel and perceive the world around us in all its versatility. However, due to the complexity and fragility of the structure of the nervous system, injuries, injuries and diseases (including genetic ones) can disrupt its well-coordinated work.

The most common diseases of the nervous system:

• Acute pathologies affecting the vessels of the brain. These include stroke, dyscirculatory encephalopathy, intracerebral hemorrhages, intracranial arterial aneurysms, etc.
• Sequelae of traumatic brain injury
• CNS infectious diseases: meningitis, encephalitis, brain abscess, poliomyelitis and others
• Multiple sclerosis
• Epilepsy
• Age-related diseases of the nervous system – Parkinson’s disease and Alzheimer’s disease
• Spinal osteochondrosis
• Genetic and inherited diseases of the nervous system. This group includes such pathologies as Leigh’s syndrome, Tourette’s syndrome, spinal muscular atrophy, Huntington’s and Batten’s diseases, etc.
• Various disorders in the work of the peripheral nervous system: neuralgia, neuritis, lumbalgia and others.

Symptoms of diseases of the nervous system

Due to the variety of forms and types of neurological disorders, it is difficult to identify common symptoms, but there are a number of the most common signs that may indicate the development of a disease of the nervous system. These include:

• Sleep disorders – insomnia
• Increased anxiety and irritability
• Decreased performance, lethargy, drowsiness
• Memory problems, decreased alertness
• Occurrence of obsessive thoughts and phobias
• Nervous tics, involuntary muscle contractions
• Headaches, migraines, pain in limbs
• Frequent fluctuations in blood pressure
• Olfactory disorders, taste disorders, vision problems

Treatment of diseases of the nervous system in a sanatorium

In case of disorders in the central or peripheral nervous system, depending on individual indications and contraindications, various procedures can be prescribed to the patient. Most often, the program for the treatment of diseases of the nervous system includes balneotherapy, water and mud therapy, various types of manual and hardware massage, and physiotherapy. In addition, during a holiday in a sanatorium, it is much easier to follow a daily schedule of activity and sleep, follow a diet and other prescriptions of the attending physician.

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AUTONOMIC NERVOUS SYSTEM • Great Russian Encyclopedia

Authors: O. L. Vinogradova, O. S. Tarasova digestion, respiration, excretion, reproduction, metabolism and growth of the organism; plays a leading role in maintaining homeostasis and adaptive reactions of the body. The term “B. n. With.” introduced in 1800 by M. Bichat, based on the fact that this part of the nervous system regulates processes that are characteristic not only of animals, but also of other organisms. Since the functions of V. n. With. cannot be arbitrarily caused or deliberately terminated, Eng. physiologist J. Langley called it autonomous.

Scheme of the structure and connections of the human autonomic nervous system: I – cervical spinal cord, II – thoracic, III – lumbar, IV – sacral. Blue indicates parasympathetic…

Anatomically and functionally V. n. With. It is divided into the sympathetic nervous system (SNS), parasympathetic nervous system (PNS) and metasympathetic nervous system (MNS). In the SNS and PNS, efferent pathways emanating from the central nervous system (CNS) consist of two series-connected neurons. The cell bodies of the first SNS neurons lie in the thoracic and lumbar spinal cord, and the PNS lie in the midbrain and medulla oblongata and in the sacral spinal cord. The second neurons (located outside the CNS) form ganglia near the spine, on the way to the organs (in the SNS), not far from the innervated organ or directly in it (in the PNS). The influence of the PNS on the work of many others. organs (heart, kidneys, etc.) is provided by Ch. arr. through the vagus nerve. For nerve fibers V. n. With. characterized by a low speed of signaling in comparison with the central nervous system. In the ganglia of the SNS and PNS, acetylcholine serves as a signal transmitter; it is also secreted from the postganglionic fibers of the PNS. In the SNS, this role is played by norepinephrine (rarely acetylcholine). Other mediators can be used along with norepinephrine and acetylcholine.

The effects of the SNS and PNS on organs are often opposite. Thus, the activation of the SNS leads to the expansion of the bronchi, an increase in the strength and frequency of contractions of the heart, the expansion of the pupils, the inhibition of the peristalsis of the gastrointestinal tract and the secretion of the digestive tract. juices, relaxation of the bladder, and activation of the PNS causes the opposite effect. The SNS and PNS have tonic (maintained) activity: for example, an increase in the heart rate can be achieved by activation of the SNS or by inhibition of the PNS. The effects may have the same direction, but differ in the features of manifestation: for example, the PNS causes copious secretion of liquid saliva, and the SNS causes a moderate secretion of viscous saliva. For a number of functions, the effects of the two departments may be summed up; thus, the PNS stimulates erection, and the SNS stimulates ejaculation. Some functions are regulated only by the PNS (for example, the work of the lacrimal glands) or the SNS (the breakdown of glycogen and fats, an increase in the efficiency of skeletal muscles, the work of the sweat glands). In many organs (except the brain, tongue, digestive glands, genital organs), vascular tone is also maintained only by the SNS. In general, the PNS is responsible for restoring the resources expended by the body, and the SNS ensures its adaptation to extreme conditions.

MHC (the term was introduced by A.D. Nozdrachev ) innervates internal organs endowed with their own motor activity: stomach and intestines ( Auerbach’s plexus , Meissner’s plexus ), bladder, heart, etc. It has its own sensitive e and intercalary neurons and is extremely diverse in the set of mediators. After damage to the MHC, the organs lose the ability to coordinate rhythmic. abbreviations.

The work of the MTC is autonomous, but is regulated by the SNC and PNC. The activity of the SNS and PNS is controlled by nerve centers (respiratory, cardiovascular, salivary, etc.), which are located in the medulla oblongata. At this level, the work of the centers can change reflexively and independently of others. These reflexes are under the control of the hypothalamus. Signals coming from the cerebral cortex also change V.’s activity. with., which provides a holistic reaction of the body to stimuli.

Parts of the nervous system that coordinate the work of internal organs in invertebrates are called visceral. Their elements are found in lower worms as formations associated with the intestinal tube, and starting with nemerteans and annelids, independent ganglia are formed. In arthropods, the system of ganglia and nerve trunks leading to the heart and stomach muscles is quite clearly identified, but only in insects are the head and tail sections separated, sometimes compared with the PNS of vertebrates, and the trunk section, comparable to the SNS.