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Overview of the Endocrine System

Overview of the Endocrine System

The endocrine system is a system of ductless glands that secrete hormones—chemical messengers that are carried for long distances.

Learning Objectives

Produce a brief overview of the endocrine system

Key Takeaways

Key Points
  • The endocrine system is a system of ductless glands that secrete hormones directly into the circulatory system to be carried long distances to other target organs that regulate key body and organ functions.
  • The major endocrine glands include the pituitary, pineal, ovaries, testes, thyroid, hypothalamus, and adrenal glands.
Key Terms
  • hormone: A molecule released by a cell or a gland in one part of the body that sends out messages affecting cells in other parts of the organism.
  • endocrine system: The system of ductless glands that secretes hormones directly into the circulatory system.

The Endocrine System

The endocrine system is a system of ductless glands that secretes hormones directly into the circulatory system to be carried long distances to other target organs regulating key body and organ functions. For example, the pineal gland, located at the base of the brain, secretes the hormone melatonin, responsible for regulating sleep patterns.

Endocrine glands are typically well vascularized and the cells comprising the tissue are typically rich in intracellular vacuoles or granules that store hormones prior to release. Endocrine signaling is typically slow to initiate but is prolonged in response; this provides a counterpoint to the more rapid and short-lived nervous system signals.

The endocrine system is in contrast to the exocrine system, which features ducted glands that secrete substances onto an epithelial surface; for example, a sweat gland. Additionally the endocrine system is differentiated from shorter distance signaling such as autocrine (a cell affecting itself), juxtacrine (a cell affecting it’s direct neighbors), and paracrine (a cell affecting other nearby cells) signaling.

Key Endocrine Glands

The major endocrine glands include the pituitary, pineal, ovaries, testes, thyroid, hypothalamus and adrenal glands, additionally other tissues such as the kidney and liver also display secondary adrenal functions.

Endocrine glands of the head and neck: The endocrine systems found in the head and neck include the hypothalamus, pineal, pituitary and thyroid glands.

Comparing the Nervous and Endocrine Systems

The nervous system and endocrine system both use chemical messengers to signal cells, but each has a different transmission speed.

Learning Objectives

Distinguish between the nervous system and the endocrine system

Key Takeaways

Key Points
  • The nervous system can respond quickly to stimuli, through the use of action potentials and neurotransmitters.
  • Responses to nervous system stimulation are typically quick but short lived.
  • The endocrine system responds to stimulation by secreting hormones into the circulatory system that travel to the target tissue. 
  • Responses to endocrine system stimulation are typically slow but long lasting.
Key Terms
  • hormone: A molecule released by a cell or a gland in one part of the body that sends out messages affecting cells in other parts of the organism.
  • neurotransmitters: Endogenous chemicals that transmit signals from a neuron to a target cell across a synapse.

The body must maintain a constant internal environment, through a process termed homeostasis, while also being able to respond and adapt to external events. The nervous and endocrine systems both work to bring about this adaptation, but their response patterns are different. The nervous system and the endocrine system use chemical messengers to signal cells, but the speed at which these messages are transmitted and the length of their effects differs.

Nervous System

The nervous system responds rapidly to stimuli by sending electrical action potentials along neurons, which in turn transmit these action potentials to their target cells using neurotransmitters, the chemical messenger of the nervous system. The response to stimuli by the nervous system is near instantaneous, although the effects are often short lived. An example is the recoil mechanism of an arm when touching something hot.

Endocrine System

The endocrine system relies on hormones to elicit responses from target cells. These hormones are synthesized in specialized glands at a distance from their target, and travel through the bloodstream or inter-cellular fluid. Upon reaching their target, hormones can induce cellular responses at a protein or genetic level.

This process takes significantly longer than that of the nervous system, as endocrine hormones must first be synthesized, transported to their target cell, and enter or signal the cell. However, although hormones act more slowly than a nervous impulse, their effects are typically longer lasting. 

Additionally, the target cells can respond to minute quantities of hormones and are sensitive to subtle changes in hormone concentration. For example, the growth hormones secreted by the pituitary gland are responsible for sustained growth during childhood.

15.1A: Overview of the Endocrine System

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  1. Key Points
  2. Key Terms
  3. The Endocrine System
  4. Key Endocrine Glands

The endocrine system is a system of ductless glands that secrete hormones—chemical messengers that are carried for long distances.

Learning Objectives

  • Produce a brief overview of the endocrine system

Key Points

  • The endocrine system is a system of ductless glands that secrete hormones directly into the circulatory system to be carried long distances to other target organs that regulate key body and organ functions.
  • The major endocrine glands include the pituitary, pineal, ovaries, testes, thyroid, hypothalamus, and adrenal glands.

Key Terms

  • hormone: A molecule released by a cell or a gland in one part of the body that sends out messages affecting cells in other parts of the organism.
  • endocrine system: The system of ductless glands that secretes hormones directly into the circulatory system.

The Endocrine System

The endocrine system is a system of ductless glands that secretes hormones directly into the circulatory system to be carried long distances to other target organs regulating key body and organ functions. For example, the pineal gland, located at the base of the brain, secretes the hormone melatonin, responsible for regulating sleep patterns.

Endocrine glands are typically well vascularized and the cells comprising the tissue are typically rich in intracellular vacuoles or granules that store hormones prior to release. Endocrine signaling is typically slow to initiate but is prolonged in response; this provides a counterpoint to the more rapid and short-lived nervous system signals.

The endocrine system is in contrast to the exocrine system, which features ducted glands that secrete substances onto an epithelial surface; for example, a sweat gland. Additionally the endocrine system is differentiated from shorter distance signaling such as autocrine (a cell affecting itself), juxtacrine (a cell affecting it’s direct neighbors), and paracrine (a cell affecting other nearby cells) signaling.

Key Endocrine Glands

The major endocrine glands include the pituitary, pineal, ovaries, testes, thyroid, hypothalamus and adrenal glands, additionally other tissues such as the kidney and liver also display secondary adrenal functions.

Endocrine glands of the head and neck: The endocrine systems found in the head and neck include the hypothalamus, pineal, pituitary and thyroid glands.

Overview of Endocrinology

Overview of Endocrinology

How is it that humans and animals maintain quite constant blood concentrations of glucose throughout their lives despite wildly varying frequencies of meals? If your blood glucose concentration drops much below 1 mg per ml, your neurons will begin to misbehave, leading ultimately to coma and death. Yet skipping breakfast is rarely life-threatening.

The answer is that a battery of chemical messengers – hormones – are secreted into blood in response to rises and falls in blood glucose concentration and stimulate metabolic pathways that pull glucose concentrations back into the normal range.

Two systems control all physiologic processes:

  • The nervous system exerts point-to-point control through nerves, similar to sending messages by conventional telephone. Nervous control is electrical in nature and fast.
  • The endocrine system broadcasts its hormonal messages to essentially all cells by secretion into blood and extracellular fluid. Like a radio broadcast, it requires a receiver to get the message – in the case of endocrine messages, cells must bear a receptor for the hormone being broadcast in order to respond.

As will be repeatedly demonstrated, the nervous and endocrine systems often act together to regulate physiology. Indeed, some neurons function as endocrine cells.

Endocrinology is the study of hormones, their receptors and the intracellular signalling pathways they invoke. Distinct endocrine organs are scattered throughout the body. These are organs that are largely or at least famously devoted to secretion of hormones, and no introduction to endocrinology would be complete without some kind of endocrine organ “map” such as that below:

In addition to the classical endocrine organs, many other cells in the body secrete hormones. Myocytes in the atria of the heart and scattered epithelial cells in the stomach and small intestine are examples of what is sometimes called the “diffuse” endocrine system. If the term hormone is defined broadly to include all secreted chemical messengers, then virtually all cells can be considered part of the endocrine system.

A final introductory comment is warranted. Pursuit of an understanding of endocrinology is complicated by several of its principles:

  • All pathophysiologic events are influenced by the endocrine milieu: There are no cell types, organs or processes that are not influenced – often profoundly – by hormone signaling.
  • All “large” physiologic effects are mediated by multiple hormones acting in concert: Normal growth from birth to adulthood, for example, is surely dependent on growth hormone, but thyroid hormones, insulin-like growth factor-1, glucocorticoids and several other hormones are also critically involved in this process.
  • There are many hormones known and little doubt that others remain to be discovered.

Consequently, endocrinology is presented here in two ways. First, the major endocrine organs and the hormones they produce are introduced, with delineation of major effects. Second, an integrated approach to understanding the multi-hormone control of several important phenomena is provided. Importantly, a considerable amount of endocrinology is incorporated into other sections. Gastrointestinal hormones, for example, are discussed throughout the section on pathophysiology of the digestive system.

Another useful overview of the endocrine system, with links to external sites, is provided at The Endocrine System

Send comments to [email protected]

Human Endocrine System

The human endocrine system modulates several processes of the body by the function of hormones. The endocrine system secretes hormones that control how bodily functions work. Thus, the human endocrine system watches over and coordinates all the systems of the body with the use of hormones.

Pituitary gland

The pituitary gland is located at the base of the human brain. The gland consists of two parts: the anterior lobe (adenohypophysis) and the posterior lobe (neurohypophysis).

The anterior lobe secretes at least seven hormones. One hormone, the human growth hormone (HGH), promotes body growth by accelerating protein synthesis. This hormone is also known as somatotropin. A deficiency of the hormone results in dwarfism; an oversecretion results in gigantism.

Another hormone of the anterior pituitary is prolactin, also called lactogenic hormone (LH). This hormone promotes breast development and milk secretion in females. A third hormone is thyroid-stimulating hormone (TSH). The function of TSH is to control secretions of hormones from the thyroid gland. A fourth hormone is adrenocorticotropic hormone (ACTH). This hormone controls the secretion of hormones from the adrenal glands.

There are three more hormones produced in the anterior lobe of the pituitary gland. The first is follicle-stimulating hormone (FSH). In females, FSH stimulates the development of a follicle, which contains the egg cell; in males, the hormone stimulates sperm production. The next hormone is luteinizing hormone (LH). In females, LH completes the maturation of the follicle and stimulates the formation of the corpus luteum, which temporarily secretes female hormones. In males, LH is interstitial cell-stimulating hormone (ICSH), which stimulates the production of male hormones in the testes. The final hormone is melanocyte-stimulating hormone (MSH), which stimulates production of the pigment melanin.

The posterior pituitary gland stores and then releases two hormones that are produced in the hypothalamus of the brain. The first hormone is antidiuretic hormone (ADH). This hormone stimulates water reabsorption in the kidneys. It is also called vasopressin. The second hormone is oxytocin, which stimulates contractions in the muscles of the uterus during birth.

Thyroid gland

The thyroid gland lies against the pharynx at the base of the neck. It consists of two lateral lobes connected by an isthmus. The gland produces thyroxine, a hormone that regulates the rate of metabolism in the body. It also produces a second hormone, calcitonin, which regulates the level of calcium in the blood.

Thyroxine production depends on the availability of iodine. A deficiency of iodine causes thyroid gland enlargement, a condition called goiter. An undersecretion of thyroxine during childhood development results in a condition known as cretinism (dwarfism with abnormal body proportions and possible mental retardation). In adults, an undersecretion can also result in myxedema (physical and mental sluggishness). Thyroxine oversecretion results in a high metabolic rate and Graves’ disease.

Parathyroid glands

The parathyroid glands are located on the posterior surfaces of the thyroid gland. They are tiny masses of glandular tissue that produce parathyroid hormone, also called parathormone. Parathyroid hormone regulates calcium metabolism in the body by increasing calcium reabsorption in the kidneys and by increasing the uptake of calcium from the digestive system.

Adrenal glands

The adrenal glands are two pyramid-shaped glands lying atop the kidneys. The adrenal glands consist of an outer portion, the adrenal cortex, and an inner portion, the medulla.

The adrenal cortex secretes a family of steroids called corticosteroids. The two main types of steroid hormones are mineralocorticoids and glucocorticoids. Mineralocorticoids such as aldosterone control mineral metabolism in the body. They accelerate mineral reabsorption in the kidneys. Mineralocorticoid secretion is regulated by ACTH from the pituitary gland. Glucocorticoids such as cortisol and cortisone control glucose metabolism and protein synthesis in the body. Glucocorticoids are also anti-inflammatory agents.

The adrenal medulla produces two hormones: epinephrine (adrenaline) and norepinephrine (noradrenaline). Epinephrine increases heart rate, blood pressure, and the blood supply to skeletal muscles. Epinephrine functions in stressful situations to promote the fight-or-flight response. Norepinephrine intensifies the effects of epinephrine. Both hormones prolong and intensify the effects of the sympathetic nervous system.

Pancreas

The pancreas is located just behind the stomach. Its endocrine portion consists of cell clusters called the islets of Langerhans.

The pancreas produces two hormones: insulin and glucagon. Insulin is a protein that promotes the passage of glucose molecules into the body cells and regulates glucose metabolism. In the absence of insulin, glucose is removed from the blood and excreted in the kidney, a condition called diabetes mellitus. Diabetes mellitus is characterized by glucose in the urine, heavy urination, excessive thirst, and a generally sluggish body metabolism.

The second pancreatic hormone, glucagon, stimulates the breakdown of glycogen to glucose in the liver. It also releases fat from the adipose tissue so the fat can be used for the production of carbohydrates.

Other endocrine glands

Among the other endocrine glands are the ovaries and testes. The ovaries secrete estrogens, which encourage the development of secondary female characteristics. The testes secrete androgens, which promote secondary male characteristics. Testosterone is an important androgen.

The pineal gland is a tiny gland in the midbrain. Its functions are largely unknown, but it seems to regulate mating behaviors and day-night cycles. The thymus gland is located in the neck tissues. It secretes thymosins, which influence the development of the T-lymphocytes of the immune system.

Prostaglandins are hormones secreted by various tissue cells. These hormones produce their effects on smooth muscles, on various glands, and in reproductive physiology. Erythropoietin is a hormone produced by the kidney cells. Erythropoietin functions in the production of red blood cells. Gastrin and secretin are hormones produced by digestive glands to influence digestive processes.

9.2 Introduction to the Endocrine System – Human Biology

Created by CK-12 Foundation/Adapted by Christine Miller

Figure 9.2.1 Enzymes, their cellular location, substrates and products in human steroidogenesis.

Your endocrine system is constantly making hormones that will regulate every body system that makes up you!  The endocrine system is an adept chemist; by making a chain of modifications to the steroid cortisol, your body can make a whole host of other hormones at a moment’s notice.

The endocrine system is a system of glands called endocrine glands that release chemical messenger molecules into the bloodstream. The messenger molecules of the endocrine system are called endocrine hormones. Other glands of the body, including sweat glands and salivary glands, also secrete substances, but not into the bloodstream. Instead, they secrete them through ducts that carry them to nearby body surfaces. These other glands are not part of the endocrine system. Instead, they are called exocrine glands.

Endocrine hormones act slowly compared with the rapid transmission of electrical messages in the nervous system. Endocrine hormones must travel through the bloodstream to the cells they affect, and this takes time. On the other hand, because endocrine hormones are released into the bloodstream, they travel throughout the body wherever blood flows. As a result, endocrine hormones may affect many cells and have body-wide effects. The effects of endocrine hormones are also longer lasting than the effects of nervous system messages. Endocrine hormones may cause effects that last for days, weeks, or even months.

The major glands of the endocrine system are shown in Figure 9.2.2. The glands in the figure are described briefly in the rest of this section. Refer to the figure as you read about the glands in the following text.

Figure 9.2.2 The endocrine system.

All of the glands labelled in Figure 9.2.2 are part of the endocrine system. Note that the ovary and testis are the only endocrine glands that differ in males and females.

Pituitary Gland

The pituitary gland is located at the base of the brain. It is controlled by the nervous system via the brain structure called the hypothalamus, to which it is connected by a thin stalk. The pituitary gland consists of two lobes, called the anterior (front) lobe and posterior (back) lobe. The posterior lobe stores and secretes hormones synthesized by the hypothalamus. The anterior lobe synthesizes and secretes its own endocrine hormones, also under the influence of the hypothalamus. One endocrine hormone secreted by the pituitary gland is growth hormone, which stimulates cells throughout the body to synthesize proteins and divide. Most of the other endocrine hormones secreted by the pituitary gland control other endocrine glands. Generally, these hormones direct the other glands to secrete either more or less of their hormones, which is why the pituitary gland is often referred to as the “master gland” of the endocrine system.

Remaining Glands of the Endocrine System

Each of the other glands of the endocrine system is summarized below. Several of these endocrine glands are also discussed in greater detail in other concepts in this chapter.

  • The thyroid gland is a large gland in the neck. Thyroid hormones (such as thyroxine) increase the rate of metabolism in cells throughout the body. They control how quickly cells use energy and make proteins.
  • The four parathyroid glands are located in the neck behind the thyroid gland. Parathyroid hormone helps keep the level of calcium in the blood within a narrow range. It stimulates bone cells to dissolve calcium and release it into the blood.
  • The pineal gland is a tiny gland located near the center of the brain. It secretes the hormone melatonin, which controls the sleep-wake cycle and several other processes. The production of melatonin is stimulated by darkness and inhibited by light. Cells in the retina of the eye detect light and send signals to a structure in the brain called the suprachiasmatic nucleus (SCN). Nerve fibres carry the signals from the SCN to the pineal gland via the autonomic nervous system.
  • The pancreas is located near the stomach. Its endocrine hormones include insulin and glucagon, which work together to control the level of glucose in the blood. The pancreas also secretes digestive enzymes into the small intestine.
  • The two adrenal glands are located above the kidneys. Adrenal glands secrete several different endocrine hormones, including the hormone adrenaline, which is involved in the fight-or-flight response. Other endocrine hormones secreted by the adrenal glands have a variety of functions. The hormone aldosterone, for example, helps regulate the balance of minerals in the body. The hormone cortisol is also an adrenal gland hormone.
  • The gonads include the ovaries in females and the testes in males. They secrete sex hormones, including testosterone (in males) and estrogen and progesterone (in females). These hormones control sexual maturation during puberty and the production of gametes (sperm or egg cells) by the gonads after sexual maturation.
  • The thymus gland is located in front of the heart. It is the site where immune system cells, called T cells, mature. T cells are critical to the adaptive immune system, in which the body adapts to specific pathogens.

Diseases of the endocrine system are relatively common. An endocrine system disease usually involves the secretion of too much or not enough of a hormone. When too much hormone is secreted, the condition is called hypersecretion.  When not enough hormone is secreted, the condition is called hyposecretion.

Hypersecretion and Hyposecretion

Figure 9.2.3 The man on the left, named Martin Van Buren Bates, is depicted in this photo standing next to a man of average size. Bates was a Civil War-era American famed for his incredibly large size. He was at least 7 feet 9 inches tall and weighed close to 500 pounds. He was normal in size at birth, but started to grow very rapidly by about age six years, presumably because of hypersecretion of growth hormone.

Hypersecretion by an endocrine gland is often caused by a tumor. A tumor of the pituitary gland, for example, can cause hypersecretion of growth hormone. If this occurs during childhood and goes untreated, it results in very long arms and legs, and an abnormally tall stature by adulthood (see Figure 9.2.3). This condition is commonly known as gigantism.

Hyposecretion by an endocrine gland is often caused by destruction of the hormone-secreting cells of the gland. As a result, not enough of the hormone is secreted. An example of this is type 1 diabetes, in which the body’s own immune system attacks and destroys cells of the pancreas that secrete insulin. This type of diabetes is generally treated with frequent injections of insulin.

Hormone Resistance

In some cases, an endocrine gland secretes a normal amount of hormone, but target cells do not respond normally to it. This may occur because target cells have become resistant to the hormone. An example of this type of endocrine disorder is type 2 diabetes. In type 2 diabetes, body cells do not respond to normal amounts of insulin. As a result, cells do not take up glucose from the blood, leading to high blood glucose levels. Insulin may or may not be needed to treat type 2 diabetes. Instead, it may be treated with lifestyle changes and non-insulin medications.

  • The endocrine system is a system of glands that release chemical messenger molecules called hormones into the bloodstream. Other glands, called exocrine glands, release substances onto nearby body surfaces through ducts. Endocrine hormones travel more slowly than nerve impulses, which are the body’s other way of sending messages. The effects of endocrine hormones, however, may be much longer lasting.
  • The pituitary gland is the master gland of the endocrine system. Most of the hormones it produces control other endocrine glands. These glands include the thyroid gland, parathyroid glands, pineal gland, pancreas, adrenal glands, gonads (testes and ovaries), and thymus gland.
  • Diseases of the endocrine system are relatively common. An endocrine disease usually involves hypersecretion or hyposecretion of a hormone. Hypersecretion is frequently caused by a tumor. Hyposecretion is often caused by destruction of hormone-secreting cells by the body’s own immune system.
  1. What is the endocrine system? What is its general function?
  2. Describe the role of the pituitary gland in the endocrine system.
  3. List three endocrine glands other than the pituitary gland. Identify their functions.
  4. Which endocrine gland has an important function in the immune system? What is that function?
  5. Name an endocrine disorder in which too much of a hormone is produced.
  6. What are two reasons people with diabetes might have signs and symptoms of inadequate insulin?
  7. Besides location, what is the main difference between the anterior lobe of the pituitary and the posterior lobe of the pituitary?

How do your hormones work? – Emma Bryce, TED-Ed, 2018.

What is congenital adrenal hyperplasia (CAH), Bijniervereniging NVACP, 2014.

Cynthia Kenyon: Experiments that hint of longer lives, TED, 2011.

 

Attributions

Figure 9.2.1

Steroidogenesis.svg by David Richfield (User:Slashme) and Mikael Häggström on Wikimedia Commons is used under a CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0/deed.en) [Derived from previous version by Hoffmeier and Settersr]

Figure 9.2.2

1801_The_Endocrine_System by OpenStax College  on Wikimedia Commons is used under a CC BY 3.0 (https://creativecommons.org/licenses/by/3.0/deed.en) license.

Figure 9.2.3

MartinVanBurenBates by unknown on Wikimedia Commons is believed to be in the public domain

 

References

Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 17.2 Endocrine system [digital image].  In Anatomy and Physiology (Section 17.1). OpenStax. https://openstax.org/books/anatomy-and-physiology/pages/17-1-an-overview-of-the-endocrine-system

Bijniervereniging NVACP. (2014, October 11). What is congenital adrenal hyperplasia (CAH)? YouTube. https://www.youtube.com/watch?v=-gNj5KoWLhE&feature=youtu.be

Häggström M, Richfield D (2014). Diagram of the pathways of human steroidogenesis. WikiJournal of Medicine 1 (1). DOI:10.15347/wjm/2014.005. ISSN 20024436 [Derived from previous version by Hoffmeier and Settersr]

TED. (2011, November 17). Cynthia Kenyon: Experiments that hint of longer lives. YouTube. https://www.youtube.com/watch?v=V48M5j-6zdE&feature=youtu.be

TED-Ed. (2018, June 21). How do your hormones work? – Emma Bryce. YouTube. https://www.youtube.com/watch?v=-SPRPkLoKp8&feature=youtu.be

 

17.1 An Overview of the Endocrine System – Anatomy & Physiology

Learning Objectives

By the end of this section, you will be able to:

  • Distinguish similarities and differences between neural and hormonal communication
  • Identify the major organs of the endocrine system and their location in the body

Communication within the human body involves the transmission of signals to control and coordinate actions in an effort to maintain homeostasis.  There are two major organ systems responsible for providing these communication pathways: the nervous system and the endocrine system.

The nervous system is primarily responsible for rapid communication throughout the body.  As discussed in previous chapters, the nervous system utilizes two types of signals – electrical and chemical (Table 17.1).  Electrical signals are sent via the generation and propagation of action potentials which move along the membrane of a cell.  Once the action potential reaches the synaptic terminal, the electrical signal is converted to a chemical signal as neurotransmitters are released into the synaptic cleft.  When the neurotransmitters binds with receptors on the receiving (post-synaptic) cell, a new electrical signal is generated and quickly continues on to its destination.  In this way, neural communication enables body functions that involve quick, brief actions, such as movement, sensation, and cognition.

In contrast, the endocrine system relies on only a single method of communication: chemical signaling (Table 1).  Hormones are the chemicals released by endocrine cells that regulate other cells in the body.   Hormones are transported primarily via the bloodstream throughout the body, where they bind to receptors on target cells, triggering a response.  Because of this dependence on the cardiovascular system for transport, this type of communication is much slower than that observed for neural signaling.  As such, hormonal communication is usually associated with activities that go on for relatively long periods of time.

External Website

Visit this link to watch an animation of the events that occur when a hormone binds to a cell membrane receptor. What is the secondary messenger made by adenylyl cyclase during the activation of liver cells by epinephrine?

In general, the nervous system involves quick responses to rapid changes in the external environment, and the endocrine system is usually slower acting—taking care of the internal environment of the body, maintaining homeostasis, and controlling reproduction. This does not mean, however, that the two systems are completely independent of one another.  Take for example the release of adrenaline from the adrenal medulla as part of the ‘fight-or-flight’ response.  Although adrenaline uses blood for transportation throughout the body, the effects are evident within seconds after the event has occurred;  how does the response happen so quickly if hormones are usually slower acting?   It occurs so rapidly because the nervous and endocrine system are both involved in the process: it is the fast action of the nervous system responding to the danger in the environment that stimulates the adrenal glands to quickly secrete their hormones.  In such a situation, the nervous system causes a rapid endocrine response to deal with sudden changes in both the external and internal environments when necessary.

Endocrine and Nervous Systems (Table 17.1)
Endocrine system Nervous system
Signaling mechanism(s) Chemical Chemical/electrical
Primary chemical signal Hormones Neurotransmitters
Distance traveled Long or short Always short
Response time Fast or slow Always fast
Environment targeted Internal Internal and external

Hormones are released by secretory cells that are derived from epithelial tissue.  Often, these cells are clustered together, forming endocrine glands.  Unlike exocrine glands, which have a duct for conveying secretions to the outside of the body (e.g., sweat gland), endocrine glands secrete substances directly into the surrounding interstitial fluid.  From there, hormones then enter the bloodstream for distribution throughout the body.

The major endocrine glands found in the human body include the pituitary gland, thyroid gland, parathyroid glands, thymus gland, adrenal glands, pineal gland, testes, and ovaries (Figure 17.1.1). While some of the glands are pure endocrine (e.g., thyroid gland), others serve both endocrine and exocrine function. For example, the pancreas contains cells that secrete digestive enzymes and juices into the small intestine (exocrine function) and cells that secrete the hormones insulin and glucagon, which regulate blood glucose levels.

In addition to the endocrine glands, major organs of the body show endocrine function including the hypothalamus, heart, kidneys, stomach, small intestine, and liver.  Moreover, adipose tissue has long been known to produce hormones, and recent research has revealed a role for bone tissue in hormone production and secretion.

Figure 17.1.1 – Endocrine System: Endocrine glands and cells are located throughout the body and play an important role in homeostasis.

In the classical definition of the endocrine system, hormones are secreted into the interstitial fluid and then diffuse into the blood or lymph for circulation throughout the body to reach target tissues.  However, in certain instances, target cells are local and do not require hormones to enter the blood.  If a chemical signal is released into the interstitial fluid and targets neighboring cells, then the activity is referred to as paracrine.  Neurotransmitter communication between a pre- and post-synaptic neuron is a good example of paracrine activity.  Alternatively, chemicals released by a cell elicit a response in the same cell that secreted it, demonstrating autocrine activity.  An example of this is type of activity is Interleukin-1, signaling molecule released in an inflammatory response that binds to receptors located on the surface of the cell releasing the molecule.

Career Connections – 

Endocrinologist

Endocrinology is a specialty in the field of medicine that focuses on the treatment of endocrine system disorders. Endocrinologists, the medical doctors who specialize in this field, are experts in treating diseases associated with hormonal systems, ranging from thyroid disease to diabetes mellitus.

Patients who are referred to endocrinologists may have signs and symptoms or blood test results that suggest excessive or impaired functioning of an endocrine gland or endocrine cells. The endocrinologist may order additional blood tests to determine whether the patient’s hormonal levels are abnormal, or they may stimulate or suppress the function of the suspect endocrine gland and then have blood taken for analysis. Treatment varies according to the diagnosis. Some endocrine disorders, such as type 2 diabetes, may respond to lifestyle changes such as modest weight loss, adoption of a healthy diet, and regular physical activity. Other disorders may require medication, such as hormone replacement, and routine monitoring by the endocrinologist. These include disorders of the pituitary gland that can affect growth and disorders of the thyroid gland that can result in a variety of metabolic problems.

Some patients experience health problems as a result of the normal decline in hormones that can accompany aging. These patients can consult with an endocrinologist to weigh the risks and benefits of hormone replacement therapy intended to boost their natural levels of reproductive hormones.

In addition to treating patients, endocrinologists may be involved in research to improve the understanding of endocrine system disorders and develop new treatments for these diseases.

Chapter Review

The body coordinates its functions through two major types of communication: neural and endocrine. Neural communication includes both electrical and chemical signaling between neurons and target cells. Endocrine communication involves chemical signaling via the release of hormones which travel through the bloodstream, where they elicit a response in target cells. Endocrine glands are ductless glands that secrete hormones. Many organs of the body with other primary functions—such as the heart, stomach, and kidneys—also have endocrine activity.

Interactive Link Questions

Visit this link to watch an animation of the events that occur when a hormone binds to a cell membrane receptor. What is the secondary messenger made by adenylyl cyclase during the activation of liver cells by epinephrine?

Critical Thinking Questions

1. Describe several main differences in the communication methods used by the endocrine system and the nervous system.

2. Compare and contrast endocrine and exocrine glands.

3. True or false: Neurotransmitters are a special class of paracrines. Explain your answer.

Glossary

autocrine
chemical signal that elicits a response in the same cell that secreted it
endocrine gland
tissue or organ that secretes hormones into the blood and lymph without ducts such that they may be transported to organs distant from the site of secretion
endocrine system
cells, tissues, and organs that secrete hormones as a primary or secondary function and play an integral role in normal bodily processes
exocrine system
cells, tissues, and organs that secrete substances directly to target tissues via glandular ducts
hormone
secretion of an endocrine organ that travels via the bloodstream or lymphatics to induce a response in target cells or tissues in another part of the body
paracrine
chemical signal that elicits a response in neighboring cells; also called paracrine factor

Solutions

Answers for Critical Thinking Questions

  1. The endocrine system uses chemical signals called hormones to convey information from one part of the body to a distant part of the body. Hormones are released from the endocrine cell into the extracellular environment, but then travel in the bloodstream to target tissues. This communication and response can take seconds to days. In contrast, neurons transmit electrical signals along their axons. At the axon terminal, the electrical signal prompts the release of a chemical signal called a neurotransmitter that carries the message across the synaptic cleft to elicit a response in the neighboring cell. This method of communication is nearly instantaneous, of very brief duration, and is highly specific.
  2. Endocrine glands are ductless. They release their secretion into the surrounding fluid, from which it enters the bloodstream or lymph to travel to distant cells. Moreover, the secretions of endocrine glands are hormones. Exocrine glands release their secretions through a duct that delivers the secretion to the target location. Moreover, the secretions of exocrine glands are not hormones, but compounds that have an immediate physiologic function. For example, pancreatic juice contains enzymes that help digest food.
  3. True. Neurotransmitters can be classified as paracrines because, upon their release from a neuron’s axon terminals, they travel across a microscopically small cleft to exert their effect on a nearby neuron or muscle cell.

Endocrine System Anatomy and Physiology

Our body cells have dynamic adventures on microscopic levels all the time. For instance, when insulin molecules, carried passively along in the blood leave the blood and bind tightly to protein receptors of nearby cells, the response it dramatic: blood borne glucose molecules begin to disappear into the cells, and cellular activity accelerates.

Functions of the Endocrine System


Despite the huge variety of hormones, there are really only two mechanisms by which hormones trigger changes in cells.

  1. Water equilibrium. The endocrine system controls water equilibrium by regulating the solute concentration of the blood.
  2. Growth, metabolism, and tissue maturation. The endocrine system controls the growth of many tissues, like the bone and muscle, and the degree of metabolism of various tissues, which aids in the maintenance of the normal body temperature and normal mental functions. Maturation of tissues, which appears in the development of adult features and adult behavior, are also determined by the endocrine system.
  3. Heart rate and blood pressure management. The endocrine system assists in managing the heart rate and blood pressure and aids in preparing the body for physical motion.
  4. Immune system control. The endocrine system helps regulate the production and functions of immune cells.
  5. Reproductive function controls. The endocrine system regulates the development and the functions of the reproductive systems in males and females.
  6. Uterine contractions and milk release. The endocrine system controls uterine contractions throughout the delivery of the newborn and stimulates milk release from the breasts in lactating females.
  7. Ion management. The endocrine system regulates Na+, K+, and Ca2+ concentrations in the blood.
  8. Blood glucose regulator. The endocrine system controls blood glucose levels and other nutrient levels in the blood.
  9. Direct gene activation. Being lipid-soluble molecules, the steroid hormones can diffuse through plasma membranes of their target cells; once inside, the steroid hormone enters the nucleus and binds to a specific receptor protein there; then, the hormone-receptor complex binds to specific sites on the cell’s DNA, activating certain genes to transcribe messenger RNA; the mRNA then is translated in the cytoplasm, resulting in the synthesis of new proteins.
  10. Second messenger system. Water-soluble, nonsteroidal hormones-protein, and peptide hormones- are unable to enter the target cells, so instead, they bind to receptors situated on the target cell’s plasma membrane and utilize a second messenger system.

Anatomy of the Endocrine System

Compared to other organs of the body, the organs of the endocrine system are small and unimpressive, however, functionally the endocrine organs are very impressive, and when their role in maintaining body homeostasis is considered, they are true giants.

Hypothalamus


The major endocrine organs of the body include the pituitary, thyroid, parathyroid, adrenal, pineal and thymus glands, the pancreas, and the gonads.

  • Hypothalamus. The hypothalamus, which is part of the nervous system, is also considered as a major endocrine organ because it produces several hormones. It is an important autonomic nervous system and endocrine control center of the brain located inferior to the thalamus.
  • Mixed functions. Although the function of some hormone-producing glands is purely endocrine, the function of others (pancreas and gonads) is mixed- both endocrine and exocrine.

Pituitary Gland


The pituitary gland is approximately the size of a pea.

  • Location. The pituitary gland hangs by a stalk from the inferior surface of the hypothalamus of the brain, where it is snugly surrounded by the “Turk’s saddle” of the sphenoid bone.
  • Lobes. It has two functional lobes- the anterior pituitary (glandular tissue) and the posterior pituitary (nervous tissue).

Hormones of the Anterior Pituitary

There are several hormones of the anterior pituitary hormones that affect many body organs.

  • Growth hormone (GH). Growth hormone is a general metabolic hormone, however,  its major effects are directed to the growth of skeletal muscles and long bones of the body; it is a protein-sparing and anabolic hormone that causes amino acids to be built into proteins and stimulates most target cells to grow in size and divide.
  • Prolactin (PRL). Prolactin is a protein hormone structurally similar to growth hormone; its only known target in humans is the breast because, after childbirth, it stimulates and maintains milk production by the mother’s breast.
  • Adrenocorticotropic hormone (ACTH). ACTH regulates the endocrine activity of the cortex portion of the adrenal gland.
  • Thyroid-stimulating hormone (TSH). TSH, also called thyrotropin hormone influences the growth and activity of the thyroid gland.
  • Gonadotropic hormones. The gonadotropic hormones regulate the hormonal activity of gonads (ovaries and testes).
  • Follicles-stimulating hormone (FSH). FSH stimulates follicle development in the ovaries; as the follicles mature, they produce estrogen and eggs that are readied for ovulation; in men, FSH stimulates sperm development by the testes.
  • Luteinizing hormone (LH). LH triggers ovulation of an egg from the ovary and causes the ruptured follicle to produce progesterone and some estrogen; in men, LH stimulates testosterone production by the interstitial cells of the testes.

Hormones of the Posterior Pituitary

The posterior pituitary is not an endocrine gland in the strict sense because it does not make the peptide hormones it releases, but it simply acts as a storage area for hormones made by hypothalamic neurons.

  • Oxytocin. Oxytocin is released in significant amount only during childbirth and in nursing women; it stimulates powerful contractions of the uterine muscle during labor, during sexual relations, and during breastfeeding and also causes milk ejection (let-down reflex) in a nursing woman.
  • Antidiuretic hormone (ADH). ADH causes the kidneys to reabsorb more water from the forming of urine; as a result, urine volume decreases and blood volume increases; in larger amounts, ADH also increases blood pressure by causing constriction of the arterioles, so it is sometimes referred to as vasopressin.

Thyroid Gland


The thyroid gland is a hormone-producing gland that is familiar to most people primarily because many obese individuals blame their overweight condition on their “glands” (thyroid).

  • Location. The thyroid gland is located at the base of the throat, just inferior to the Adam’s apple, where it is easily palpated during a physical examination.
  • Lobes. It is a fairly large gland consisting of two lobes joined by a central mass, or isthmus.
  • Composition. Internally, the thyroid gland is composed of hollow structures called follicles, which store a sticky colloidal material.
  • Types of thyroid hormones. Thyroid hormone often referred to as the body’s major metabolic hormone, is actually two active, iodine-containing hormones, thyroxine or T4, and triiodothyronine or T3.
  • Thyroxine. Thyroxine is the major hormone secreted by the thyroid follicles.
  • Triiodothyronine. Most triiodothyronine is formed at the target tissues by conversion of the thyroxine to triiodothyronine.
  • Function. Thyroid hormone controls the rate at which glucose is “burned” oxidized, and converted to body heat and chemical energy; it is also important for normal tissue growth and development.
  • Calcitonin. Calcitonin decreases blood calcium levels by causing calcium to be deposited in the bones; calcitonin is made by the so-called parafollicular cells found in the connective tissues between the follicles.

Parathyroid Glands


The parathyroid glands are mostly tiny masses of glandular tissue.

  • Location. The parathyroid glands are located on the posterior surface of the thyroid gland.
  • Parathormone. The parathyroids secrete parathyroid hormone (PTH) or parathormone, which is the most important regulator of calcium ion homeostasis of the blood; PTH is a hypercalcemic hormone (that is, it acts to increase blood levels of calcium), whereas calcitonin is a hypocalcemic hormone.; PTH also stimulates the kidneys and intestines to absorb more calcium.

Adrenal Glands


Although the adrenal gland looks like a single organ, it is structurally and functionally two endocrine organs in one.

Hormones of the Adrenal Cortex

The adrenal cortex produces three major groups of steroid hormones, which are collectively called corticosteroids– mineralocorticoids, glucocorticoids, and sex hormones.

  • Mineralocorticoids. The mineralocorticoids, primarily aldosterone, are produced by the outermost adrenal cortex cell layer; mineralocorticoids are important in regulating the mineral (or salt) content of the blood, particularly the concentrations of sodium and potassium ions and they also help in regulating the water and electrolyte balance in the body.
  • Renin. Renin, am enzyme produced by the kidneys when the blood pressure drops, also cause the release of aldosterone by triggering a series of reactions that form angiotensin II, a potent stimulator of aldosterone release.
  • Atrial natriuretic peptide (ANP). ANP prevents aldosterone release, its goal being to reduce blood volume and blood pressure.
  • Glucocorticoids. The middle cortical layer mainly produces glucocorticoids, which include cortisone and cortisol; glucocorticoids promote normal cell metabolism and help the body to resist long-term stressors, primarily by increasing blood glucose levels, thus it is said to be a hyperglycemic hormone; it also reduce pain and inflammation by inhibiting some pain-causing molecules called prostaglandins.
  • Sex hormones. Both male and female sex hormones are produced by the adrenal cortex throughout life in relatively small amounts; although the bulk of sex hormones produced by the innermost cortex layer are androgens (male sex hormones), some estrogens (female sex hormones), are also formed.

Hormones of the Adrenal Medulla

The adrenal medulla, like the posterior pituitary, develops from a knot of nervous tissue.

  • Catecholamines. When the medulla is stimulated by sympathetic nervous system neurons, its cells release two similar hormones, epinephrine, also called adrenaline, and norepinephrine (noradrenaline), into the bloodstream; collectively, these hormones are referred to as catecholamines.
  • Function. Basically, the Catecholamines increase heart rate, blood pressure, and blood glucose levels and dilate the small passageways of the lungs; the catecholamines of the adrenal medulla prepare the body to cope with a brief or short-term stressful situation and cause the so-called alarm stage of the stress response.

Pancreatic Islets


The pancreas, located close to the stomach in the abdominal cavity, is a mixed gland.

  • Islets of Langerhans.The islets of Langerhans also called pancreatic islets, are little masses of hormone-producing tissue that are scattered among the enzyme-producing acinar tissue of the pancreas.
  • Hormones. Two important hormones produced by the islet cells are insulin and glucagon.
  • Islet cells. Islet cells act as fuel sensors, secreting insulin and glucagon appropriately during fed and fasting states.
  • Beta cells. High levels of glucose in the blood stimulate the release of insulin from the beta cells of the islets.
  • Alpha cells. Glucagon’s release by the alpha cells of the islets is stimulated by low blood glucose levels.
  • Insulin. Insulin acts on just about all the body cells and increases their ability to transport glucose across their plasma membranes; because insulin sweeps glucose out of the blood, its effect is said to be hypoglycemic.
  • Glucagon. Glucagon acts as an antagonist of insulin; that is, it helps to regulate blood glucose levels but in a way opposite that of insulin; its action is basically hyperglycemic and its primary target organ is the liver, which it stimulates to break down stored glycogen into glucose and release the glucose into the blood.

Pineal Gland


The pineal gland, also called the pineal body, is a small cone-shaped gland.

  • Location. The pineal gland hangs from the roof of the third ventricle of the brain.
  • Melatonin. Melatonin is the only hormone that appears to be secreted in substantial amounts by the pineal gland; the levels of melatonin rise and fall during the course of the day and night; peak levels occur at night and make us drowsy as melatonin is believed to be the “sleep trigger” that plays an important role in establishing the body’s day-night cycle.

Thymus Gland


The thymus gland is large in infants and children and decreases in size throughout adulthood.

  • Location. The thymus gland is located in the upper thorax, posterior to the sternum.
  • Thymosin. The thymus produces a hormone called thymosin and others that appear to be essential for normal development of a special group of white blood cells (T-lymphocytes, or T cells) and the immune response.

Gonads


Main Article: Female Reproductive System and Male Reproductive System

The female and male gonads produce sex hormones that are identical to those produced by adrenal cortex cells; the major difference are the source and relative amount produced.

Hormones of the Ovaries

The female gonads or ovaries are a pair of almond-sized organs.

  • Location. The female gonads are located in the pelvic cavity.
  • Steroid hormones. Besides producing female sex cells, ovaries produce two groups of steroid hormones, estrogen, and progesterone.
  • Estrogen. Alone, the estrogens are responsible for the development of sex characteristics in women at puberty; acting with progesterone, estrogens promote breast development and cyclic changes in the uterine lining (menstrual cycle).
  • Progesterone. Progesterone acts with estrogen to bring about the menstrual cycle; during pregnancy, it quiets the muscles of the uterus so that an implanted embryo will not be aborted and helps prepare breast tissue for lactation.

Hormones of the Testes

The testes of the male are paired oval organs in a sac.

  • Location. The testes are suspended in a sac, the scrotum, outside the pelvic cavity.
  • Male sex hormones. In addition to male sex cells, or sperm, the testes also produce male sex hormones, or androgens, of which testosterone is the most important.
  • Testosterone. At puberty, testosterone promotes the growth and maturation of the reproductive system organs to prepare the young man for reproduction; it also causes the male’s secondary sex characteristics to appear and stimulates male sex drive; Testosterone is also necessary for the continuous production of sperm.

Other Hormone-Producing Tissues and Organs

Besides the major endocrine organs, pockets of hormone-producing cells are found in fatty tissue and in the walls of the small intestine, stomach, kidneys, and heart- organs whose chief functions have little to do with hormone production.

Placenta


The placenta is a remarkable organ formed temporarily in the uterus of pregnant women.

  • Function. In addition to its roles as the respiratory, excretory, and nutrition delivery systems for the fetus, it also produces several proteins and steroid hormones that help to maintain the pregnancy and pave the way for delivery of the baby.
  • Human chorionic gonadotropin. During very early pregnancy, a hormone called human chorionic gonadotropin (hCG) is produced by the developing embryo and then by the fetal part of the placenta; hCG stimulates the ovaries to continue producing estrogen and progesterone so that the lining of the uterus is not sloughed off in the menses.
  • Human placental lactogen (hPL). hPL works cooperatively with estrogen and progesterone in preparing the breasts for lactation.
  • Relaxin. Relaxin, another placental hormone, causes the mother’s pelvic ligaments and the pubic symphysis to relax and become more flexible, which eases birth passage.

Physiology of the Endocrine System

Although hormones have widespread effects, the major processes they control are reproduction, growth, and development; mobilizing the body’s defenses against stressors; maintaining electrolyte, water, and nutrient balance of the blood; and regulating cellular metabolism and energy balance.

The Chemistry of Hormones


The key to the incredible power of the endocrine glands is the hormones they produce and secrete.

  • Hormones. Hormones may be defined as chemical substances that are secreted by endocrine cells into the extracellular fluids and regulate the metabolic activity of other cells in the body.
  • Classification. Although many different hormones are produced, nearly all of them can be classified chemically as either amino acid-based molecules (including proteins, peptides, and amines) or steroids.
  • Steroid hormones. Steroid hormones (made from cholesterol) include the sex hormones made by the gonads and hormones produced by the adrenal cortex.
  • Amino acid-based hormones. All the others are nonsteroidal amino acid derivatives.

Mechanisms of Hormone Action


Although the blood-borne hormones circulate to all the organs of the body, a given hormone affects only certain tissue cells or organs.

  • Target cells. For a target cell to respond to the hormone, specific protein receptors must be present on its plasma membrane or in its interior to which that hormone can attach; only when this binding occurs can the hormone influence the workings of cells.
  • Function of hormones. The hormones bring about their effects on, the body cells primarily by altering cellular activity- that is, by increasing or decreasing the rate of a normal, or usual, metabolic process rather than stimulating a new one.
  • Changes in hormone binding. The precise changes that follow hormone binding depend on the specific hormone and the target cell type, but typically one or more of the following occurs:
  1. Changes in plasma membrane permeability or electrical state.
  2. Synthesis of protein or certain regulatory molecules (such as enzymes) in the cell.’
  3. Activation or inactivation of enzymes.
  4. Stimulation of mitosis.
  5. Promotion of secretory activity.

Control of Hormone Release


What prompts the endocrine glands to release or not release their hormones?

  • Negative feedback mechanisms. Negative feedback mechanisms are the chief means of regulating blood levels of nearly all hormones.
  • Endocrine gland stimuli. The stimuli that activate the endocrine organs fall into three major categories- hormonal, humoral, and neural.
  • Hormonal stimuli. The most common stimulus is a hormonal stimulus, in which the endocrine organs are prodded into action by other hormones; for example, hypothalamic hormones stimulate the anterior pituitary gland to secrete its hormones, and many anterior pituitary hormones stimulate other endocrine organs to release their hormones into the blood.
  • Humoral stimuli. Changing blood levels of certain ions and nutrients may also stimulate hormone release, and this is referred to as humoral stimuli; for example, the release of parathyroid hormone (PTH) by cells of the parathyroid glands is prompted by decreasing blood calcium levels.
  • Neural stimuli. In isolated cases, nerve fibers stimulate hormone release, and the target cells are said to respond to neural stimuli; a classic example is sympathetic nervous system stimulation of the adrenal medulla to release norepinephrine and epinephrine during periods of stress.

Practice Quiz: Endocrine System Anatomy and Physiology


Here’s a 10-item quiz about the study guide. Please visit our nursing test bank page for more NCLEX practice questions.

1. The following are the functions of the endocrine system, except?

A. Regulates immune system
B. Controls reproductive function
C. Regulate heart rate and blood pressure
D. Water balance
E. Direct blood flow

1. Answer: E. Direct blood flow

  • E. This is a function of the peripheral circulation wherein the system directs blood to tissues when increased blood flow is required to maintain homeostasis.
  • A: The endocrine system helps control the production and function of the immune cells.
  • B: The endocrine system helps controls the development and functions of the reproductive systems in males and females.
  • C: The endocrine system helps regulate heart rate and blood pressure and helps prepare the body for physical exertion.
  • D: The endocrine system regulates water balance by controlling the solute concentration of the blood.

2. The primary function of T3 and T4 is to:

A. Reduce blood glucose levels
B. Release calcitonin
C. Regulate bone growth
D. Increase metabolic rate

2. Answer: D. Increase metabolic rate

  • D: T3 and T4 are released throughout the body to direct the body’s metabolism. They stimulate all cells within the body to increase metabolic rate.
  • A: Insulin lowers blood glucose levels, and promotes the formation of glycogen.
  • B: Calcitonin is a hormone that the C-cells in the thyroid gland produces and release.  It opposes the action of the parathyroid hormone, helping to regulate the blood’s calcium and phosphate levels.
  • C: Body growth is controlled by growth hormone (GH), produced by the anterior pituitary gland.

3. Antidiuretic hormone and oxytocin are stored and released by the:

A. Adrenal cortex
B. Posterior pituitary gland
C. Thyroid gland
D. Pineal gland

3. Answer: B. Posterior pituitary gland

  • B: The posterior pituitary gland releases two hormones (antidiuretic hormone and oxytocin).
  • A: The two major hormones produced by the adrenal cortex are the mineralocorticoids and the glucocorticoids.
  • C: The Thyroid gland is involved in the production of the hormones T3 (triiodothyronine) and T4 (thyroxine).
  • D: The main hormone produced and secreted by the pineal gland is melatonin.

4. Which hormone stimulates the male testes to produce sperm and stimulates the development of the follicle in the female on a monthly cycle.

A. Luteinizing hormone
B. Somatostatin
C. Follicle-stimulating hormone
D. Thymosin

4. Answer: C. Follicle-stimulating hormone

  • C: Follicle-stimulating hormone stimulates the growth of ovarian follicles in the ovary in females and acts on the Sertoli cells of the testes to stimulate sperm production (spermatogenesis) in males.
  • A: Luteinizing hormone. For women, the hormone stimulates the ovaries to produce oestradiol. For men, it stimulates the production of testosterone from Leydig cells in the testes
  • B: The primary function of somatostatin is to inhibit the production of other hormones and also prevent the unnatural rapid reproduction of cells (such as those in tumors).
  • D: Thymosin enhances the ability of the immune system to function.

5. A client with a history of hypertension is admitted due to primary hyperaldosteronism. This diagnosis indicates that the client’s hypertension is caused by excessive hormone secretion from which gland?

A. Pancreas
B. Adrenal cortex
C. Thymus gland
D. Adrenal medulla

5. Answer: B. Adrenal cortex

  • B: Excessive aldosterone secretion in the adrenal cortex is responsible for the client’s hypertension.
  • A: Pancreas secretes hormones involved in glucose metabolism.
  • C: Thymus gland secretes thymosin, which stimulates the development of disease-fighting T cells.
  • D: Adrenal medulla secretes the catecholamines (epinephrine and norepinephrine).

6. The mineralocorticoids produced by the adrenal glands are produced within the?

A. Parafollicular cells
B. Zona reticularis
C. Zona glomerulosa
D. Zona fasciculata

6. Answer: C. Zona glomerulosa

  • C: The zona glomerulosa is responsible for synthesis of aldosterone as well as some other corticosteroids such as glucocorticoid.
  • A: Calcitonin is produced by the parafollicular cells found in the connective tissues between the follicles.
  • B&D: Zona reticularis acts in collaboration with the Zona fasciculata and is primarily involved in the synthesis as well as secretion of different sex hormones that work as a substitute for gonadal hormones.

7. Which of the following glands is both an endocrine gland and an exocrine gland, except?

A. Pancreas
B. Kidney
C. Gonads
D. Pituitary gland

7. Answer: D. Pituitary gland

  • D: Pituitary gland has only an endocrine component.
  • A, B, and C: Endocrine component of glands with both an endocrine and an exocrine function. These include the pancreas, kidney, and gonads.

8. Which of the following is not true with melatonin?

A. Melatonin induces heat loss, reduces arousal and related brain activity and delays production of cortisol.
B. It helps regulate biological rhythms such as sleep and wake cycles.
C. The secretion of melatonin is inhibited by darkness and triggered by light.
D. The pineal gland produces and secretes the hormone.

8. Answer: C. The secretion of melatonin is inhibited by darkness and triggered by light.

  • C: Light exposure resets the circadian rhythm of melatonin and acutely inhibits melatonin synthesis while the secretion of melatonin is triggered by darkness.

9. Part of the effect of growth hormone is influenced by a group of protein chemical signals called:

A. Somatomedin-C.
B. Gonadotropins
C. Prostaglandin
D. Prolactin

9. Answer: A. Somatomedin-C.

  • A: Somatomedin C also called, insulin-like growth factor 1 (IGF-1),  is a protein that plays an important role in childhood growth and continues to have anabolic effects in adults.
  • B: Gonadotropins are hormones that bind to membrane-bound receptors on the cells of the gonads.
  • C: Prostaglandins play an important role in regulating smooth muscle contraction and inflammation.
  • D: Prolactin helps promote the development of the breast during pregnancy and stimulates the production of milk in the breast following pregnancy.

10. A client arrived at the emergency department with a possible diagnosis of hyperparathyroidism. The nurse anticipates which serum electrolytes finding would be abnormal? Select all that apply

A. Sodium
B. Calcium
C. Chloride
D. Potassium
E. Phosphorus

10. Answer: B. Calcium, E. Phosphorus

  • B & E: A client with a parathormone deficiency has abnormal calcium and phosphorus values because parathormone regulates these two electrolytes.
  • A, C, & D: Potassium, chloride, sodium have no effect on a parathyroid hormone deficiency

See Also


Other anatomy and physiology study guides:

Further Reading


  1. Nursing Diagnosis Handbook: An Evidence-Based Guide to Planning Care
  2. Medical-Surgical Nursing: Assessment and Management of Clinical Problems
  3. Medical-Surgical Nursing: Patient-Centered Collaborative Care
  4. Saunders Comprehensive Review for the NCLEX-RN Examination
  5. Brunner & Suddarth’s Textbook of Medical-Surgical Nursing

Prokopyevsk | Summary of coronavirus in Kuzbass over the past day

192 cases of coronavirus infection were detected in Kuzbass over the past day:

Novokuznetsk – 36, Kemerovo – 35, Mezhdurechensk – 20, Prokopyevsk – 17, Osinniki – 9, Belovo – 8, Myski – 8, Leninsk-Kuznetskiy – 7, Kaltan – 6, Belovsky MR – 6, Anzhero-Sudzhensk – 5, Yurga – 5, Mariinsky MR – 4, Tashtagolsky MR – 4, Yurginsky MO – 4, Taiga – 3, Guryevsky MO – 3, Kiselevsk – 2, Polysaevo – 2, Prokopyevsky MO – 2, Yashkinsky MO – 2, Krasnobrodsky – 1, Kemerovo MO – 1, Leninsk-Kuznetskiy MO – 1, Tisulskiy MO – 1.

6 patients died. A woman born in 1961 developed bilateral polysegmental pneumonia. The disease proceeded against the background of diabetes mellitus. She lived in Prokopyevsk.

A woman born in 1943 developed bilateral polysegmental pneumonia. The disease proceeded against the background of diabetes mellitus. She lived in Novokuznetsk.

A man born in 1973 developed bilateral polysegmental pneumonia. He lived in Novokuznetsk.

A woman born in 1951 developed bilateral polysegmental pneumonia.The disease proceeded against the background of the pathology of the central nervous system. She lived in Polysaevo.

A man born in 1949 developed bilateral polysegmental pneumonia. The disease proceeded against the background of pathology of the cardiovascular system, central nervous system. He lived in Kiselevsk.

A woman born in 1951 developed bilateral polysegmental pneumonia. The disease proceeded against the background of pathology of the cardiovascular system, diabetes mellitus, chronic diseases of the kidneys, gastrointestinal tract, and pathology of the endocrine system.She lived in Prokopyevsk.

192 patients recovered. Thus, in Kuzbass, 45,312 people have recovered from the coronavirus.

In total, 1,893 patients diagnosed with COVID-19 receive medical care in the region.

12,741 people are in medical hospitals, observatories and 14-day isolation at home. This is reported by the regional operational headquarters for coronavirus.

More news about the event:

A working meeting was held between the Governor of Kuzbass and the Chairman of the Election Commission of the Kemerovo Region – Kuzbass

A little more than a month remains before a single voting day in 2021.
20:56 08/11/2021 Election Commission of the Kemerovo Region – Kemerovo

Preparation for elections 2021

Kuzbass is preparing for elections. They will take place over 3 days – from 17 to 19 September.
18:38 08/11/2021 TVN – Novokuznetsk

90,026 In Kuzbass, 192 new cases of coronavirus infection were detected per day, 6 patients died 90,027

Over the past day, 192 cases of coronavirus infection were detected in Kuzbass: Novokuznetsk – 36, Kemerovo – 35, Mezhdurechensk – 20, Prokopyevsk – 17,
16:50 11.08.2021 Law enforcement portal Kuzbass – Kemerovo

Summary of coronavirus in Kuzbass over the past day

192 cases of coronavirus infection were detected in Kuzbass over the past day:

Novokuznetsk – 36, Kemerovo – 35, Mezhdurechensk – 20, Prokopyevsk – 17,
15:44 11.08.2021 Prokopievsk.ru – Prokopyevsk

Over the past day, 192 cases of coronavirus infection were detected in Kuzbass

August 11 – TOWN.Over the past day, 192 cases of coronavirus infection were detected in Kuzbass: Novokuznetsk – 36, Kemerovo – 35, Mezhdurechensk – 20, Prokopyevsk – 17,
12:51 11.08.2021 Gorodok – Kiselevsk

Coronavirus: Elections in view of the pandemic

We continue to inform the residents of Mezhdurechensk about the news on the topic of coronavirus.***

According to the Headquarters for the protection of public health of Kuzbass at 11.
12:13 11.08.2021 Newspaper Kontakt – Mezhdurechensk

Coronavirus kaleidoscope. 08/11/2021

Today, August 11, marks one year since the registration of the first Russian vaccine “Sputnik V”.
12:12 08/11/2021 KuzPress.Ru – Kemerovo

Operations headquarters: data on people infected with coronavirus in Kuzbass on August 11

Six people died.

On the morning of August 11 in the Kemerovo region, another 192 patients were diagnosed with coronavirus infection.
12:11 11.08.2021 With you – Kemerovo

Synopsis as of 11:00, 11 Aug

Over the past day, 192 cases of coronavirus infection were detected in Kuzbass: Novokuznetsk – 36, Kemerovo – 35, Mezhdurechensk – 20, Prokopyevsk – 17,
11:50 11.08.2021 Belovsky District – Belovo

Coronavirus was detected in another 192 residents of Kuzbass. Novokuznetsk leads

Over the past day, the coronavirus was confirmed in another 192 residents of the Kemerovo region.
11:42 11.08.2021 Newspaper Kuzbass – Kemerovo

Summary as of 11:00 on August 11 from Public Health Headquarters

Over the past day, 192 cases of coronavirus infection were detected in Kuzbass: Novokuznetsk – 36, Kemerovo – 35, Mezhdurechensk – 20, Prokopyevsk – 17,
11:41 11.08.2021 Regional Administration – Kemerovo

Kuzbass summary on coronavirus for August 11 published

Over the past day, 192 cases of coronavirus infection were detected in Kuzbass: Novokuznetsk – 36, Kemerovo – 35, Mezhdurechensk – 20, Prokopyevsk – 17,
11:22 11.08.2021 STRC Kuzbass – Kemerovo

Six people died from coronavirus in Kuzbass per day

Physicians diagnosed COVID-19 in 192 new patients.In Kuzbass, 6 people, four women and two men, have died from coronavirus over the past day.
11:21 11.08.2021 Sibdepo.Ru – Kemerovo

The territory of Kuzbass became known, where 192 new cases of coronavirus were detected

Over the past day, the coronavirus was confirmed in 192 people in 25 cities and regions of Kuzbass.
11:12 11.08.2021 A42.Ru – Kemerovo

More than 1,030 people with confirmed COVID-19 died in Kuzbass

In Kuzbass, the coronavirus claimed the lives of six people per day, the regional operational headquarters said.
11:12 11.08.2021 A42.Ru – Kemerovo

Coronavirus in Kuzbass: 192 people fell ill, 6 patients died

Novokuznetsk became the leader in morbidity

More than 1800 people continue treatment for coronavirus

Photo: Alexey Volkhonsky / V1.RU

192 residents of the Kemerovo region have confirmed coronavirus over the past day.
11:10 11.08.2021 Ngs42.Ru – Kemerovo

A teenager died from coronavirus in Kuzbass

According to the regional headquarters for combating coronavirus infection, as of August 10, 2021, 193 cases were identified.
07:22 08/11/2021 Nk-Tv – Novokuznetsk

Summary as of August 10 (11:00)

Over the past day, 193 cases of coronavirus infection were detected in Kuzbass: Kemerovo – 37, Novokuznetsk – 35, Prokopyevsk – 19, Mezhdurechensk – 19, Yurga – 11,
00:42 11.08.2021 Chastnik-M.Ru – Mezhdurechensk

Related news from neighboring regions:

90,026 69 new cases of covid in Mordovia, three women died 90,027

69 cases of coronavirus were detected in Mordovia per day, 47 people were discharged with recovery.
12:42 08/11/2021 Capital C – Saransk

Three women died in a day from coronavirus in Mordovia

69 cases of coronavirus were detected in Mordovia per day, 47 people were discharged with recovery.
12:31 08/11/2021 Info-rm.Com – Saransk

90,026 In the Bryansk region, 228 people were diagnosed with coronavirus per day 90,027

In 56,524 people have been diagnosed with coronavirus in the Bryansk region since the beginning of the pandemic (in 228 over the past day).
19:31 08/10/2021 IA Nash Bryansk.ru – Bryansk

In the Bryansk region, 10 more people died from coronavirus per day 90 027

In the Bryansk region, another 10 people have died from coronavirus in the last 24 hours.
16:37 08/10/2021 Newspaper Bryanskie Novosti – Bryansk

Two died, 21 patients had pneumonia: all about the situation with covid in the Kaliningrad region on Tuesday

In the Kaliningrad region, 150 patients with coronavirus have the disease in the form of ARVI, 21 were diagnosed with pneumonia.
14:05 10.08.2021 Klops.Ru – Kaliningrad

90,026 398 people became infected with coronavirus per day in the Irkutsk region 90,027

During the day, 398 people were infected with coronavirus in the Irkutsk region. In total, 89,806 cases have been registered in the region since the beginning of the pandemic, according to the headquarters on August 10.
20:04 08/10/2021 LiveAngarsk.Ru – Angarsk

Up-to-date information on coronavirus in Kirovo-Chepetsk on August 10

In the city of Kirovo-Chepetsk, as of August 10, over the past day, 2 hospitalized with coronavirus were registered (total 2080).
13:55 08/10/2021 City of Ch. – Kirovo-Chepetsk

90,026 During the day, 9 Tula residents died from coronavirus

In the Tula region on August 10, the death of 9 patients who had previously contracted coronavirus was confirmed.
12:33 08/10/2021 Our Life is Warm

12 Novosibirsk residents died from coronavirus per day

Photo: Om1.ru, coronavirus 198 patients were diagnosed with COVID-19.

Over the past day in the Novosibirsk region, 198 people have become infected with the coronavirus.
16:25 08/10/2021 Om1.Ru – Omsk

90,026 More than 20 people died from coronavirus in the Samara region per day 90,027

The data is provided by the federal operational headquarters on August 10, 2021.

In the Samara region, 21 people with a diagnosis of coronavirus died per day.
12:04 08/10/2021 RegionSamara.Ru – Samara

24 more covid patients died in the Voronezh region

The disease has given complications.

During the day in the Voronezh region, another 24 covid patients died from coronavirus.
11:47 08/10/2021 State Television and Radio Broadcasting Company Voronezh – Voronezh

Three more Novgorodians died from coronavirus

Over the past day, three deaths of coronavirus were registered in the Novgorod region.
12:43 08/10/2021 Novgorod.Ru – Veliky Novgorod

90,026 12 residents of the Novosibirsk region died from coronavirus per day 90,027

Photo: pixabay.com

In the Novosibirsk region, on the morning of August 10, 54 693 cases of coronavirus were registered.
14:25 08/10/2021 4S-Info.Ru – Novosibirsk

Five elderly chicken women died due to coronavirus

Since the beginning of the pandemic in the Kursk region, 1,152 people have died due to the coronavirus.
10:37 08/10/2021 Kurskaya Pravda – Kursk

COVID-19 and diabetes: doctors talked about the risks for patients

Photo from progorod archive Patients with such a disease should be under the special control of doctors

On the risk of active development of pre-existing diabetes mellitus in patients who have recovered from the new COVID-19 virus,
09:02 10.08.2021 ProGorod.Ru – Kirov

90,026 398 people became infected with coronavirus per day in the Irkutsk region 90,027

During the day, 398 people were infected with coronavirus in the Irkutsk region. In total, 89,806 cases have been registered in the region since the beginning of the pandemic, according to the headquarters on August 10.
14:21 08/10/2021 Irk.Ru – Irkutsk

Voronezh.Coronavirus. August 9, 2021

In the last 24 hours, 17 patients with covid have died.

Over the past 24 hours, coronavirus has been confirmed in 471 residents of the Voronezh region.
18:42 08/09/2021 State TV and Radio Company Voronezh – Voronezh

90,026 In the Orenburg region, the number of patients on mechanical ventilation decreased by a third 90,027

The number of patients with coronavirus in hospitals in the Orenburg region exceeds 1,700 people.
16:01 09.08.2021 Orenburg.Media – Orenburg

In Russia, coronavirus was confirmed in several thousand patients 90,027

Operational information on the situation with the coronavirus as of August 9 of this year.
12:48 09.08.2021 Penza-Post.Ru – Penza

90,000 In the Volgograd region, 5 deaths were registered per day

A woman, 34 years old, lived in Volzhsky.

Feeling the first signs of malaise, she did not seek medical help, she was treated on her own. A few days later, due to the deterioration of her condition, she asked for medical help. Hospitalized in GBUZ “GKB No. 3”.

Diagnosed with COVID-19 with bilateral pneumonia.

Concomitant diseases: chronic diseases of the cardiovascular system, endocrine system; chronic autoimmune disease.

Man, 59 years old, lived in the Oktyabrsky district.

Feeling the first signs of malaise, he sought medical help. He was treated on an outpatient basis, without positive dynamics, in connection with which the man was hospitalized in the GBUZ “VOKND”.

Diagnosed with COVID-19 with bilateral pneumonia.

Concomitant diseases: chronic diseases of the cardiovascular system.

Woman, 80 years old, lived in Surovikino.

Feeling the first signs of malaise, she sought medical help. Hospitalized in the Kalachevskaya Central Regional Hospital.

Diagnosed with COVID-19 with bilateral pneumonia.

Concomitant diseases: chronic diseases of the cardiovascular system.

A man, 60 years old, lived in the Gorodishchensky district.

Feeling the first signs of malaise, he called the ambulance team. He refused the proposed hospitalization. After 4 days, he called an ambulance again. Hospitalized in the State Institution “KB No. 4”.

Diagnosed with COVID-19 with bilateral pneumonia.

Concomitant diseases: chronic diseases of the cardiovascular system, endocrine system; respiratory organs.

Woman, 84 years old, lived in the Svetloyarsk region.

Feeling the first signs of malaise, she asked for medical help at the place of residence after 3 days. Based on the results of the examination, she was hospitalized in the State Healthcare Institution “Hospital No. 22”.

Diagnosed with COVID-19 with bilateral pneumonia.

Concomitant diseases: chronic diseases of the cardiovascular system.

More than a hundred. Summary of coronavirus for the last day

Over the past day, 102 cases of coronavirus infection were detected in Kuzbass: Kemerovo – 33, Novokuznetsk – 12, Mezhdurechensk – 9, Yurga – 9, Osinniki – 8, Prokopyevsk – 7, Kemerovo Municipal District – 4, Guryevsky municipal district – 3, Belovo – 2, Kaltan – 2, Myski – 2, Tashtagolsky municipal district – 2, Anzhero-Sudzhensk – 1, Leninsk-Kuznetskiy – 1, Krapivinsky municipal district – 1, Mariinsky municipal district – 1, Prokopyevsky municipal District – 1, Promyshynovsky Municipal District – 1, Topkinsky Municipal District – 1, Yurginsky Municipal District – 1, Yashkinsky Municipal District – 1.

5 patients died. A woman born in 1941 developed bilateral polysegmental pneumonia. The disease proceeded against the background of pathology of the cardiovascular system, diabetes mellitus. She lived in Novokuznetsk.

A man born in 1967 developed bilateral polysegmental pneumonia. The disease proceeded against the background of the pathology of the endocrine system, diseases of the gastrointestinal tract. He lived in Kemerovo.

A man born in 1949 developed bilateral polysegmental pneumonia.The disease proceeded against the background of pathology of the cardiovascular system, blood disease. He lived in Novokuznetsk.

A man born in 1945 developed bilateral polysegmental pneumonia. The disease proceeded against the background of concomitant pathology of the cardiovascular system, chronic kidney disease. He lived in Anzhero-Sudzhensk.

A woman born in 1933 developed bilateral polysegmental pneumonia. The disease proceeded against the background of the pathology of the central nervous system. She lived in Kemerovo.

71 patients recovered. Thus, in Kuzbass, 36,842 people have recovered from the coronavirus.

In total, 718 patients diagnosed with COVID-19 receive medical care in the region.