Adrenal Glands and The Autonomic Nervous System Adrenal Glands and The Autonomic Nervous System Add Remove The question: The adrenal glands are in part controlled by the sympathetic and parasympathetic branches of the autonomic nervous system . Name the hormones involved in this regulation and the functions of each I know that the sympathetic is adrenaline and noradrenaline. I can't find what the parasympathetic hormones are. I know they slow heart rate and reduce blood pressure and induce a state of relaxation. I can find the functions of the hormones if someone could point me in the direction of where to find out which hormones I need to write about! Thanks Solution Preview To find the answer, we must find out the anatomy of the adrenal glands which will give you the innervation, and then look for the physiology which will give you what they secret and the effects. The adrenal glands are divided into medulla (inner part) and cortex (outer part). The innervation of the medulla derives from the sympathetic ganglions. In fact the adrenal medulla cells are considered modified sympathetic postganglionic neurons (McCorryl,. 2007).

The medulla produces epinephrine (adrenaline), norepinephrine (noradrenaline) and dopamine. "Norepinephrine causes a marked increase in peripheral vascular resistance as a result of ... Solution Summary Discussion of the relationship between the hormones secreted by the adrenal glands and the sympathetic and parasympathetic branches of the autonomic nervous system. $2.19 Adrenal Glands | Johns Hopkins Medicine Health Library Adrenal Glands: What You Need to Know Adrenal glands, also known as suprarenal glands, are small, triangular-shaped glands located on top of both kidneys. Adrenal glands produce hormones that help regulate your metabolism, immune system, blood pressure, response to stress and other essential functions. Adrenal glands are composed of two parts — the cortex and the medulla — which are each responsible for producing different hormones. When adrenal glands don’t produce enough hormones, this can lead to adrenal insufficiency (Addison’s disease). Adrenal glands may develop nodules that can be benign or malignant. These nodules may produce excessive amounts of certain hormones leading to various health issues.

Anatomy of the Adrenal Glands An adrenal gland is made of two main parts: The adrenal cortex is the outer region and also the largest part of an adrenal gland. It is divided into three separate zones: zona glomerulosa, zona fasciculata and zona reticularis. Each zone is responsible for producing specific hormones. The adrenal medulla is located inside the adrenal cortex in the center of an adrenal gland. It produces several “stress hormones,” including adrenaline. The adrenal cortex and adrenal medulla are enveloped in an adipose capsule that forms a protective layer around an adrenal gland. Hormones of the Adrenal Glands The role of the adrenal glands in your body is to release certain hormones directly into the bloodstream. Many of these hormones have to do with how the body responds to stress, and some are vital to existence. Both parts of the adrenal glands — the adrenal cortex and the adrenal medulla — perform distinct and separate functions. Each zone of the adrenal cortex secretes a specific hormone. The key hormones produced by the adrenal cortex include: Cortisol Cortisol is a glucocorticoid hormone produced by the zona fasciculata that plays several important roles in the body.

It helps control the body’s use of fats, proteins and carbohydrates; suppresses inflammation; regulates blood pressure; increases blood sugar; and can also decrease bone formation. This hormone also controls the sleep/wake cycle. It is released during times of stress to help your body get an energy boost and better handle an emergency situation. How Adrenal Glands Work to Produce Cortisol Adrenal glands produce hormones in response to signals from the hypothalamus and the pituitary gland in the brain. For example, for the adrenal gland to produce cortisol: The hypothalamus produces corticotropin-releasing hormone (CRH) that stimulates the pituitary gland to secrete adrenocorticotropin hormone (ACTH). The ACTH then stimulates the adrenal glands to make and release cortisol hormones into the blood. Normally, both the hypothalamus and the pituitary gland can sense whether the blood has the right amount of cortisol in it. If there is too much or too little cortisol, these glands respectively change the amount of CRH and ACTH that gets released. Excess cortisol production can occur from nodules in the adrenal gland or excess production of ACTH from a tumor in the pituitary gland or other source.

Aldosterone This mineralocorticoid hormone produced by the zona glomerulosa plays a central role in regulating blood pressure and certain electrolytes (sodium and potassium). Aldosterone sends signals to the kidneys, resulting in the kidneys absorbing more sodium into the bloodstream and releasing potassium into the urine. This means that aldosterone also helps regulate the blood pH by controlling the levels of electrolytes in the blood. DHEA and Androgenic Steroids These hormones produced by the zona reticularis are weak male hormones. They are precursor hormones that are converted in the ovaries into female hormones (estrogens) and in the testes into male hormones (androgens). However, estrogens and androgens are produced in much larger amounts by the ovaries and testes. Epinephrine (Adrenaline) and Norepinephrine (Noradrenaline) The adrenal medulla, the inner part of an adrenal gland, controls hormones that help you cope with physical and emotional stress. The main hormones secreted by the adrenal medulla include epinephrine (adrenaline) and norepinephrine (noradrenaline), which have similar functions.

Among other things, these hormones are capable of increasing the heart rate and force of heart contractions, increasing blood flow to the muscles and brain, relaxing smooth muscles, and assisting in sugar metabolism. They also control the squeezing of the blood vessels (vasoconstriction), helping maintain blood pressure and increasing it in response to stress. Like several other hormones produced by the adrenal glands, epinephrine and norepinephrine are often activated in stressful situations when your body needs additional resources and energy to endure unusual strain. Adrenal Gland Disorders The two common ways in which adrenal glands cause health issues are by producing too little or too much of certain hormones, which leads to hormonal imbalances. These abnormalities of the adrenal function can be caused by various diseases of the adrenal glands or the pituitary gland. Adrenal Insufficiency Adrenal insufficiency is a rare disorder. It may be caused by disease of the adrenal glands (primary adrenal insufficiency, Addison’s disease) or by diseases in the hypothalamus or the pituitary (secondary adrenal insufficiency). It is the opposite of Cushing syndrome and is characterized by low levels of cortisol (and aldosterone in the primary form).

The symptoms include weight loss, poor appetite, nausea and vomiting, fatigue, darkening of skin (only in primary adrenal insufficiency), abdominal pain, etc. The causes of primary adrenal insufficiency may include autoimmune disorders, fungal and other infections, cancer (rarely), and genetic factors. Although adrenal insufficiency usually develops over time, it can also appear suddenly as an acute adrenal failure (adrenal crisis). It has similar symptoms, but the consequences are more serious, including coma, shock and seizures. These may develop if the condition is left untreated. Congenital Adrenal Hyperplasia Adrenal insufficiency can also result from a genetic disorder called congenital adrenal hyperplasia. Children who are born with this disorder are missing an essential enzyme necessary to produce cortisol, aldosterone or both. At the same time, they often experience excess of androgen, which may lead to male characteristics in girls and precocious puberty in boys. Congenital adrenal hyperplasia can remain undiagnosed for years depending on the severity of the enzyme deficiency. In more severe cases, infants may suffer from dehydration, vomiting and failure to thrive. Overactive Adrenal Glands Sometimes, adrenal glands may develop nodules that produce too much of certain hormones.

Nodules 4 centimeters or larger and nodules that show certain features on imaging may be cancerous. Both benign and cancerous nodules may produce excessive amounts of certain hormones, which often is referred to as an overactive adrenal gland . Excess of Cortisol: Cushing Syndrome Cushing syndrome results from excessive production of cortisol from the adrenal glands. The symptoms may include weight gain and fatty deposits in certain areas of the body, such as the face, below the back of the neck and in the abdomen; thinning arms and legs; purple stretch marks on the abdomen; facial hair; fatigue; muscle weakness; easily bruised skin; high blood pressure; diabetes; and other health issues. Excess cortisol production can also be triggered by overproduction of ACTH by a benign tumor in the pituitary gland. This is known as Cushing Disease.

Another common cause of Cushing syndrome is excessive and prolonged consumption of external steroids, such as prednisone or dexamethasone, which are prescribed to treat many autoimmune or inflammatory diseases (e.g., lupus, rheumatoid arthritis, asthma, inflammatory bowel disease, multiple sclerosis, etc.) Excess of Aldosterone: Hyperaldosteronism Hyperaldosteronism results from overproduction of aldosterone from one or both adrenal glands. This is characterized by increase in blood pressure that often requires many medications to control. Some people can develop low potassium levels in the blood, which can cause muscle aches, weakness and spasms. When the cause is a benign tumor in one adrenal gland, the disease is called Conn syndrome. Excess of Adrenaline or Noradrenaline: Pheochromocytoma Pheochromocytoma is a tumor that results in excess production of adrenaline or noradrenaline by the adrenal medulla that often happens in bursts. Occasionally, neural crest tissue, which is similar to the adrenal medulla, may be the cause of overproduction of these hormones. This condition is called a paraganglioma.

Pheochromocytomas may cause persistent or sporadic high blood pressure that may be difficult to control with regular medications. Other symptoms include headaches, sweating, tremors, anxiety and rapid heartbeat. Some people are genetically predisposed to developing this type of tumor. Adrenal Cancer Malignant adrenal tumors (adrenal cancer), such as adrenocortical carcinoma, are rare and often have spread to other organs and tissues by the time they are diagnosed. These tumors tend to grow fairly large and can reach several inches in diameter. Adrenal cancer may cause adrenal glands to produce excess of one or more hormones accompanied by corresponding symptoms, as listed above. You may also experience abdominal pain or flank pain and a feeling of fullness if the adrenal tumor gets very large. Not all cancers found in adrenal glands start there. Most adrenal cancers are secondary cancers that start elsewhere in the body and spread to the adrenal glands. Experience Our Care Adrenal Glands About Watch and Favorite Watch Watching this resources will notify you when proposed changes or new versions are created so you can keep track of improvements that have been made. Favorite Favoriting this resource allows you to save it in the “My Resources” tab of your account.

There, you can easily access this resource later when you’re ready to customize it or assign it to your students. Adrenal Glands Adrenal glands are composed of the adrenal cortex and medulla; both produce hormones that control essential body functions and responses. Learning Objective Distinguish between the hormones produced by the adrenal cortex and adrenal medulla and the functions they regulate Key Points The two major hormones produced by the adrenal cortex are the mineralocorticoids , which regulate the salt and water balance, and the glucocorticoids , which can regulate blood glucose and the body's inflammatory response. There are three main glucocorticoids: cortisol, corticosterone, and cortisone. The adrenal medulla produces the hormones epinephrine and norepinephrine ; these hormones regulate heart rate, breathing rate, cardiac muscle contractions, blood pressure, and blood glucose levels. Terms Full Text Adrenal Glands Adrenal glands are a pair of ductless glands located above the kidneys . Through hormonal secretions , the adrenal glands regulate many essential functions in the body, including biochemical balances that influence athletic training and general stress response. The adrenal glands consist of an outer adrenal cortex and an inner adrenal medulla, which secrete different hormones.

Adrenal glands are located on top of the kidneys. These glands are composed of the adrenal cortex and the adrenal medulla. Adrenal Cortex The adrenal cortex is made up of layers of epithelial cells and associated capillary networks. These layers form three distinct regions: an outer zona glomerulosa that produces mineralocorticoids; a middle zona fasciculata that produces glucocorticoids; and an inner zona reticularis that produces androgens , which are sex hormones that promote masculinity. Androgens are produced in small amounts by the adrenal cortex in both males and females. They do not affect sexual characteristics and may supplement sex hormones released from the gonads . The hormones made by the adrenal cortex supply long-term responses to stress. The two major hormones produced are the mineralocorticoids and the glucocorticoids. The mineralocorticoids regulate the salt and water balance, leading to the increase of blood volume and blood pressure. The main mineralocorticoid is aldosterone , which regulates the concentration of sodium ions in urine, sweat, pancreas, and saliva. Aldosterone release from the adrenal cortex is stimulated by a decrease in blood concentrations of sodium ions, blood volume, or blood pressure, or by an increase in blood potassium levels.

The glucocorticoids regulate increases in blood glucose and also reduce the body's inflammatory response. The three main glucocorticoid hormones are cortisol, corticosterone, and cortisone. The glucocorticoids stimulate the synthesis of glucose and gluconeogenesis (converting a non-carbohydrate to glucose) by liver cells. They also promote the release of fatty acids from adipose tissue. These hormones increase blood glucose levels to maintain levels within a normal range between meals. Cortisol is one of the most active glucocorticoids. It usually reduces the effects of inflammation or swelling throughout the body. It also stimulates the production of glucose from fats and proteins , which is a process referred to as gluconeogenesis. Aldosterone is one example of a mineralcorticoid. It signals the tubules in the kidney nephrons to reabsorb sodium while secreting or eliminating potassium. If sodium levels are low in the blood, the kidney secretes more renin , an enzyme that stimulates the formation of angiotensin from a molecule made from the liver. Angiotensin stimulates aldosterone secretion. As a result, more sodium is reabsorbed as it enters the blood.

Aldosterone, the major mineralcorticoid, stimulates the cells of the distal convoluted tubules of the kidneys to decrease re-absorption of potassium and increase re-absorption of sodium. This in turn leads to an increased re-absorption of chloride and water. These hormones, together with such hormones as insulin and glucagon , are important regulators of the ionic environment of the internal fluid. Adrenal Medulla The adrenal medulla contains large, irregularly-shaped cells that are closely associated with blood vessels. These cells are innervated by pre-ganglionic autonomic nerve fibers from the central nervous system . The adrenal medulla contains two types of secretory cells: one that produces epinephrine (adrenaline) and another that produces norepinephrine (noradrenaline). Epinephrine is the primary adrenal medulla hormone, accounting for 75 to 80 percent of its secretions. Epinephrine and norepinephrine increase heart rate, breathing rate, cardiac muscle contractions, blood pressure, and blood glucose levels. They also accelerate the breakdown of glucose in skeletal muscles and stored fats in adipose tissue.

The release of epinephrine and norepinephrine is stimulated by neural impulses from the sympathetic nervous system . Secretion of these hormones is stimulated by acetylcholine release from pre-ganglionic sympathetic fibers innervating the adrenal medulla. These neural impulses originate from the hypothalamus in response to stress to prepare the body for the fight-or-flight response. What is the Stress Response | Simply Psychology What is the Stress Response? Stress is a biological and psychological response experienced on encountering a threat that we feel we do not have the resources to deal with. A stressor is the stimulus (or threat) that causes stress, e.g. exam, divorce, death of loved one, moving house, loss of job. Sudden and severe stress generally produces: Increase in heart rate Increase in breathing (lungs dilate) Decrease in digestive activity (don’t feel hungry) Liver released glucose for energy Firstly, our body judges a situation and decides whether or not it is stressful. This decision is made based on sensory input and processing (i.e. the things we see and hear in the situation) and also on stored memories (i.e. what happened the last time we were in a similar situation).

If the situation is judged as being stressful, the hypothalamus (at the base of the brain) is activated. The hypothalamus in the brain is in charge of the stress response. When a stress response is triggered, it sends signals to two other structures: the pituitary gland, and the adrenal medulla. These short term responses are produced by The Fight or Flight Response via the Sympathomedullary Pathway (SAM). Long term stress is regulated by the Hypothalamic Pituitary-Adrenal (HPA) system. The Hypothalamic Pituitary-Adrenal (HPA) System The stressor activates the Hypothalamic Pituitary Axis The hypothalamus stimulates the pituitary gland The pituitary gland secretes adrenocorticotropic hormone (ACTH) ACTH stimulates the adrenal glands to produce the hormone corticosteroid Cortisol enables the body to maintain steady supplies of blood sugar Adequate and steady blood sugar levels help person to cope with prolonged stressor, and helps the body to return to normal The adrenal cortex releases stress hormones called cortisol. This have a number of functions including releasing stored glucose from the liver (for energy) and controlling swelling after injury.

The immune system is suppressed while this happens. Sympathomedullary Pathway (SAM) The hypothalamus also activates the adrenal medulla. The adrenal medulla is part of the autonomic nervous system (ANS). The ANS is the part of the peripheral nervous system that acts as a control system, maintaining homeostasis in the body. These activities are generally performed without conscious control. The adrenal medulla secretes the hormone adrenaline. This hormone gets the body ready for a fight or flight response. Physiological reaction includes increased heart rate. Adrenaline lead to the arousal of the sympathetic nervous system and reduced activity in the parasympathetic nervous system. Adrenaline creates changes in the body such as decreases (in digestion) and increases (sweating, increased pulse and blood pressure). Once the ‘threat’ is over the parasympathetic branch takes control and brings the body back into a balanced state. No ill effects are experienced from the short-term response to stress and it further has survival value in an evolutionary context. Evaluation Measuring stress hormones gives an objective measure of stress. Fight/flight response can be seen in all mammals in response to threats.

Weakness There is considerable variation in level and type of hormones released by different people and in response to different stressors  not a simple physiological process. People without adrenal glands need hormonal supplements to survive stress. Symington (1955) found that conscious dying patients showed different stress reactions to unconscious ones. Suggests that psychological factors play a role. References Currie, A. R., & Symington, T. (1955). The pathology of the pituitary and adrenal glands in systemic disease in man. Proceedings of the Royal Society of Medicine, 48(11), 908. How to cite this article: McLeod, S. A. (2010). What is the Stress Response. Retrieved from NDRF Anatomical Structure of the System The nervous system comprises the brain and various types of nerves, including afferent nerves (from the Latin, ad = towards; ferro = I carry), which carry sensory impulses from all parts of the body to the brain and efferent nerves (ex = from; ferro = I carry) through which "messages" are conducted from the brain to the muscles and all of the organs of the body.

The somatic part of the nervous system has sensory components which convey sensations from the eyes, the nose and other sensory organs to the brain (mainly the cerebral cortex) where most of the impulses reach our awareness, and motor components transmitting impulses to the skeletal muscles in the limbs and trunk permitting voluntary control of movements. The autonomic nervous system conveys sensory impulses from the blood vessels, the heart and all of the organs in the chest, abdomen and pelvis through nerves to other parts of the brain (mainly the medulla, pons and hypothalamus). These impulses often do not reach our consciousness, but elicit largely automatic or reflex responses through the efferent autonomic nerves, thereby eliciting appropriate reactions of the heart, the vascular system, and all the organs of the body to variations in environmental temperature, posture, food intake, stressful experiences and other changes to which all individuals are exposed. There are two major components of the autonomic nervous system, the sympathetic and the parasympathetic systems. The afferent nerves subserving both systems convey impulses from sensory organs, muscles, the circulatory system and all the organs of the body to the controlling centers in the medulla, pons and hypothalamus.

From these centers efferent impulses are conveyed to all parts of the body by the parasympathetic and sympathetic nerves. The impulses of the parasympathetic system reach the organs of the body through the cranial nerves # 3, 7, 9, & 10, and some sacral nerves to the eyes, the gastrointestinal system, and other organs. The sympathetic nerves reach their end-organs through more devious pathways down the spinal cord to clusters of sympathetic nerve bodies (ganglia) alongside the spine where the messages are relayed to other nerve bodies (or neurons) that travel to a large extent with the blood vessels to all parts of the body. Through these nervous pathways, the autonomic nerves convey stimuli resulting in largely unconscious, reflex, bodily adjustments such as in the size of the pupil, the digestive functions of the stomach and intestines, the rate and depth of respiration and dilatation or constriction of the blood vessels. Transmission of Autonomic Stimuli Like other nerves, those of the autonomic nervous system convey their messages to the appropriate end organs (blood vessels, viscera, etc.) by releasing transmitter substances to which the receptors of the target cells are responsive.

The most important of these transmitters in the autonomic nervous system are acetylcholine and norepinephrine. In the parasympathetic system, acetylcholine is responsible for most of these transmissions between the afferent and efferent nerves of the system and between the efferent nerve endings and the cells or organs that they subserve. Acetylcholine also serves to transmit nerve-to-nerve messages in the afferent nerves and the brain centers of the sympathetic nervous system. However, the final transmission of messages from the sympathetic nerves to the end-organs or cells that they innervate is conveyed by the release of norepinephrine (noradrenaline) with at least one important exception, namely the sympathetically conveyed stimulus to the sweat glands which is transmitted by acetylcholine. A stimulus to contraction of the blood vessels is required in order to maintain the blood pressure when we arise from bed in the morning, so as to prevent fainting from excessive pooling of blood in the lower body. This stimulus is conveyed by norepinephrine release within the walls of the blood vessels from the nerve endings of the sympathetic nerves that innervate each blood vessel.

(a) The Parasympathetic System When a stimulus arises in an organ, such as a bright light shone into the eyes, the message is conducted through sensory fibers to the midbrain to give rise to an appropriate stimulus that travels through the parasympathetic fibers of the oculomotor (third cranial) nerves to the pupils, resulting in automatic contraction of the pupillary muscles to constrict the aperture and so reduce the amount of light reaching the sensory cells in the retinae of the eyes. Similarly, the stimuli associated with the entry of food into the stomach are conveyed by afferent fibers of the vagus nerve to the command station or nucleus of the vagus in the brain whence messages are automatically conveyed through efferent fibers of the vagus back to the stomach. These stimulate the secretion of gastric juices and peristaltic contractions of the stomach to mix the food with the secreted digestive juices and gradually to convey the gastric contents into the intestines where a similar process is initiated through essentially the same parasympathetic nerve pathways. Fortunately, emptying of the rectum and of the urinary bladder is not entirely automatic but is subject to parasympathetic impulses that are voluntarily controlled.

Thus, filling of the urinary bladder with urine stimulates stretch-sensitive receptors in the wall of the bladder whence the message is conveyed to the midbrain where the stimulus to bladder contraction and opening of the sphincters is voluntarily initiated to allow the discharge of the contained urine. Similarly the very complex requirements of giving birth to a baby are initiated by stimuli to dilatation of the cervix, and involuntary contractions of the uterine musculature with delivery of the fetus assisted by voluntary contraction of the abdominal muscles. (b) The Sympathetic Nervous System The sympathetic nervous system is even more automatic and only exceptionally susceptible to any voluntary control. When the environmental temperature is raised on a hot summers day, the increased temperature initiates several automatic responses. Thermal receptors convey stimuli to sympathetic control centers of the brain from which inhibitory messages travel along the sympathetic nerves to the blood vessels of the skin resulting in dilatation of the cutaneous blood vessels, thereby greatly increasing the flow of blood to the surface of the body from where heat is lost by radiation from the surface of the body.

Dilatation of the blood vessels in this way tends to lower the blood pressure and to promote oozing or transudation of the fluid from the capillaries which may result in swelling of the dependent limbs. Thus, fine adjustments in sympathetic control of vascular contraction and "tone" are required to prevent excessive vascular dilatation and undue reduction in blood pressure. Otherwise, this might result in severe gravitational pooling of blood in the lower limbs thereby reducing blood flow to the brain and causing fainting spells, to which individuals with impaired sympathetic nervous functions are very susceptible. The sympathetic nervous system responds to environmental heat in another important way. The rise in body temperature is sensed by the hypothalamic center from which stimuli emanate via sympathetic nerves to the sweat glands, resulting in appropriate sweating. This serves to cool the body by the loss of heat resulting from evaporation of the sweat, aided by a cool breeze. The only really voluntary input that we have to facilitate cooling in a warm environment is to get into a pool, a cold shower, or an air-conditioned room! We cannot voluntarily influence the dilatation of our blood vessels or the adequacy of our sweating in response to heat in other ways.

Control of the rate and strength of cardiac contractions is also under the predominant control of the sympathetic nervous system. Thus, a fall in blood pressure resulting from traumatic injury causing blood loss is sensed by pressure-sensitive parts of the arteries called baroreceptors. Evidence of reduced arterial distension is sensed by these baroreceptors and conveyed by the parasympathetic (mainly the glossopharyngeal) nerves to the cardiovascular control center in the medulla, called the nucleus tractus solitarii. From these nuclei sympathetic stimuli conveyed by the cardiac nerves cause acceleration of the heart rate, probably complemented by simultaneous reduction in the parasympathetic stimuli via the vagus nerves which slow the heart rate. Although pain, anxiety, fear and injuries or blood loss would involuntarily increase the sympathetic stimulation to cardiac acceleration, most of us are unable to influence either this effect or the consequences of blood loss per se on cardiac acceleration. (c) The Adrenal Medulla The central part of the adrenal glands (the adrenal medulla) contains a collection of sympathetic nerve cells specialized in at least two important respects.

Because of their proximity to the adrenal cortex which surrounds the medulla and secretes hydrocortisone (or cortisol), the neurons of the medulla are able to synthesize not only norepinephrine but also, by attaching a methyl group to this compound, epinephrine (or adrenaline). The adrenal medulla is the only source of more than trivial amounts of epinephrine that enters the blood stream. The second aspect of specialization of the adrenal medulla is in its responses, via the sympathetic efferent nerves that reach it, to specific types of stimuli that have little or no effect on the rest of the autonomic nervous system. Thus, whereas changing from recumbency to the upright posture activates mainly the sympathetic neurons of the blood vessels where norepinephrine is released with resulting elevation mainly of plasma norepinephrine levels, a fall in blood sugar induced by an injection or excessive release of insulin causes a predominant increase in plasma epinephrine, the concentration of which may rise to 3 or 4 times the concomitant level of plasma norepinephrine.

Situations such as emotional excitement, fear, apprehension, psychic distress, panic reactions, sexual activity and fight-or-flight stimuli probably activate many parts of the sympathetic nervous systems including the adrenal medullae. It is evident, therefore, that while we are not constantly aware of the activity of the autonomic nervous system as we are of unusual sensory and motor events, the normal functioning of the autonomic nervous system day and night, from heart-beat to heart-beat, plays a largely unconscious but vital role in our livelihood. It is not surprising, therefore, that autonomic abnormalities, though they are usually more difficult to recognize than a severe pain, a sensory loss or paralysis of a limb, may be even more important in impairing the quality and even jeopardizing the continuation of life. David H.P. Streeten, MB, DPhil, FRCP, FACP Emeritus Professor of Medicine Endocrine System: Discover the Anatomy and Function of Glands Oxytocin Antidiuretic hormone (ADH) All of the releasing and inhibiting hormones affect the function of the anterior pituitary gland. TRH stimulates the anterior pituitary gland to release thyroid-stimulating hormone.

GHRH and GHIH work to regulate the release of growth hormone—GHRH stimulates growth hormone release, GHIH inhibits its release. GnRH stimulates the release of follicle stimulating hormone and luteinizing hormone while CRH stimulates the release of adrenocorticotropic hormone. The last two hormones—oxytocin and antidiuretic hormone—are produced by the hypothalamus and transported to the posterior pituitary, where they are stored and later released. Pituitary Gland The pituitary gland , also known as the hypophysis, is a small pea-sized lump of tissue connected to the inferior portion of the hypothalamus of the brain. Many blood vessels surround the pituitary gland to carry the hormones it releases throughout the body. Situated in a small depression in the sphenoid bone called the sella turcica, the pituitary gland is actually made of 2 completely separate structures: the posterior and anterior pituitary glands. Posterior Pituitary: The posterior pituitary gland is actually not glandular tissue at all, but nervous tissue instead.

The posterior pituitary is a small extension of the hypothalamus through which the axons of some of the neurosecretory cells of the hypothalamus extend. These neurosecretory cells create 2 hormones in the hypothalamus that are stored and released by the posterior pituitary: Oxytocin triggers uterine contractions during childbirth and the release of milk during breastfeeding. Antidiuretic hormone (ADH) prevents water loss in the body by increasing the re-uptake of water in the kidneys and reducing blood flow to sweat glands. Anterior Pituitary: The anterior pituitary gland is the true glandular part of the pituitary gland. The function of the anterior pituitary gland is controlled by the releasing and inhibiting hormones of the hypothalamus. The anterior pituitary produces 6 important hormones: Thyroid stimulating hormone (TSH), as its name suggests, is a tropic hormone responsible for the stimulation of the thyroid gland. Adrenocorticotropic hormone (ACTH) stimulates the adrenal cortex, the outer part of the adrenal gland, to produce its hormones.

Follicle stimulating hormone (FSH) stimulates the follicle cells of the gonads to produce gametes—ova in females and sperm in males. Luteinizing hormone (LH) stimulates the gonads to produce the sex hormones—estrogens in females and testosterone in males. Human growth hormone (HGH) affects many target cells throughout the body by stimulating their growth, repair, and reproduction. Prolactin (PRL) has many effects on the body, chief of which is that it stimulates the mammary glands of the breast to produce milk. Pineal Gland The pineal gland is a small pinecone-shaped mass of glandular tissue found just posterior to the thalamus of the brain. The pineal gland produces the hormone melatonin that helps to regulate the human sleep-wake cycle known as the circadian rhythm. The activity of the pineal gland is inhibited by stimulation from the photoreceptors of the retina. This light sensitivity causes melatonin to be produced only in low light or darkness. Increased melatonin production causes humans to feel drowsy at nighttime when the pineal gland is active.

Thyroid Gland The thyroid gland is a butterfly-shaped gland located at the base of the neck and wrapped around the lateral sides of the trachea. The thyroid gland produces 3 major hormones: Calcitonin Triiodothyronine (T3) Thyroxine (T4) Calcitonin is released when calcium ion levels in the blood rise above a certain set point. Calcitonin functions to reduce the concentration of calcium ions in the blood by aiding the absorption of calcium into the matrix of bones. The hormones T3 and T4 work together to regulate the body’s metabolic rate. Increased levels of T3 and T4 lead to increased cellular activity and energy usage in the body. Parathyroid Glands The parathyroid glands are 4 small masses of glandular tissue found on the posterior side of the thyroid gland. The parathyroid glands produce the hormone parathyroid hormone (PTH), which is involved in calcium ion homeostasis. PTH is released from the parathyroid glands when calcium ion levels in the blood drop below a set point. PTH stimulates the osteoclasts to break down the calcium containing bone matrix to release free calcium ions into the bloodstream.

PTH also triggers the kidneys to return calcium ions filtered out of the blood back to the bloodstream so that it is conserved. Adrenal Glands The adrenal glands are a pair of roughly triangular glands found immediately superior to the kidneys. The adrenal glands are each made of 2 distinct layers, each with their own unique functions: the outer adrenal cortex and inner adrenal medulla. Adrenal cortex: The adrenal cortex produces many cortical hormones in 3 classes: glucocorticoids, mineralocorticoids, and androgens. Glucocorticoids have many diverse functions, including the breakdown of proteins and lipids to produce glucose. Glucocorticoids also function to reduce inflammation and immune response. Mineralocorticoids, as their name suggests, are a group of hormones that help to regulate the concentration of mineral ions in the body. Androgens, such as testosterone, are produced at low levels in the adrenal cortex to regulate the growth and activity of cells that are receptive to male hormones. In adult males, the amount of androgens produced by the testes is many times greater than the amount produced by the adrenal cortex, leading to the appearance of male secondary sex characteristics.

Adrenal medulla: The adrenal medulla produces the hormones epinephrine and norepinephrine under stimulation by the sympathetic division of the autonomic nervous system. Both of these hormones help to increase the flow of blood to the brain and muscles to improve the “fight-or-flight” response to stress. These hormones also work to increase heart rate, breathing rate, and blood pressure while decreasing the flow of blood to and function of organs that are not involved in responding to emergencies. Pancreas The pancreas is a large gland located in the abdominal cavity just inferior and posterior to the stomach . The pancreas is considered to be a heterocrine gland as it contains both endocrine and exocrine tissue. The endocrine cells of the pancreas make up just about 1% of the total mass of the pancreas and are found in small groups throughout the pancreas called islets of Langerhans. Within these islets are 2 types of cells—alpha and beta cells. The alpha cells produce the hormone glucagon, which is responsible for raising blood glucose levels. Glucagon triggers muscle and liver cells to break down the polysaccharide glycogen to release glucose into the bloodstream.

The beta cells produce the hormone insulin, which is responsible for lowering blood glucose levels after a meal. Insulin triggers the absorption of glucose from the blood into cells, where it is added to glycogen molecules for storage. Gonads The gonads—ovaries in females and testes in males—are responsible for producing the sex hormones of the body. These sex hormones determine the secondary sex characteristics of adult females and adult males. Testes: The testes are a pair of ellipsoid organs found in the scrotum of males that produce the androgen testosterone in males after the start of puberty. Testosterone has effects on many parts of the body, including the muscles, bones, sex organs, and hair follicles. This hormone causes growth and increases in strength of the bones and muscles, including the accelerated growth of long bones during adolescence. During puberty, testosterone controls the growth and development of the sex organs and body hair of males, including pubic, chest, and facial hair. In men who have inherited genes for baldness testosterone triggers the onset of androgenic alopecia, commonly known as male pattern baldness. Ovaries: The ovaries are a pair of almond-shaped glands located in the pelvic body cavity lateral and superior to the uterus in females.

The ovaries produce the female sex hormones progesterone and estrogens. Progesterone is most active in females during ovulation and pregnancy where it maintains appropriate conditions in the human body to support a developing fetus. Estrogens are a group of related hormones that function as the primary female sex hormones. The release of estrogen during puberty triggers the development of female secondary sex characteristics such as uterine development, breast development, and the growth of pubic hair. Estrogen also triggers the increased growth of bones during adolescence that lead to adult height and proportions. Thymus The thymus is a soft, triangular-shaped organ found in the chest posterior to the sternum. The thymus produces hormones called thymosins that help to train and develop T-lymphocytes during fetal development and childhood. The T-lymphocytes produced in the thymus go on to protect the body from pathogens throughout a person’s entire life. The thymus becomes inactive during puberty and is slowly replaced by adipose tissue throughout a person’s life. Other Hormone Producing Organs In addition to the glands of the endocrine system, many other non-glandular organs and tissues in the body produce hormones as well.

Heart: The cardiac muscle tissue of the heart is capable of producing the hormone atrial natriuretic peptide (ANP) in response to high blood pressure levels. ANP works to reduce blood pressure by triggering vasodilation to provide more space for the blood to travel through. ANP also reduces blood volume and pressure by causing water and salt to be excreted out of the blood by the kidneys. Kidneys: The kidneys produce the hormone erythropoietin (EPO) in response to low levels of oxygen in the blood. EPO released by the kidneys travels to the red bone marrow where it stimulates an increased production of red blood cells. The number of red blood cells increases the oxygen carrying capacity of the blood, eventually ending the production of EPO. Digestive System: The hormones cholecystokinin (CCK), secretin, and gastrin are all produced by the organs of the gastrointestinal tract. CCK, secretin, and gastrin all help to regulate the secretion of pancreatic juice, bile, and gastric juice in response to the presence of food in the stomach. CCK is also instrumental in the sensation of satiety or “fullness” after eating a meal.

Adipose: Adipose tissue produces the hormone leptin that is involved in the management of appetite and energy usage by the body. Leptin is produced at levels relative to the amount of adipose tissue in the body, allowing the brain to monitor the body’s energy storage condition. When the body contains a sufficient level of adipose for energy storage, the level of leptin in the blood tells the brain that the body is not starving and may work normally. If the level of adipose or leptin decreases below a certain threshold, the body enters starvation mode and attempts to conserve energy through increased hunger and food intake and decreased energy usage. Adipose tissue also produces very low levels of estrogens in both men and women. In obese people the large volume of adipose tissue may lead to abnormal estrogen levels. Placenta: In pregnant women, the placenta produces several hormones that help to maintain pregnancy. Progesterone is produced to relax the uterus, protect the fetus from the mother’s immune system , and prevent premature delivery of the fetus. Human chorionic gonadotropin (HCG) assists progesterone by signaling the ovaries to maintain the production of estrogen and progesterone throughout pregnancy.

Local Hormones: Prostaglandins and leukotrienes are produced by every tissue in the body (except for blood tissue) in response to damaging stimuli. These two hormones mainly affect the cells that are local to the source of damage, leaving the rest of the body free to function normally. Prostaglandins cause swelling, inflammation, increased pain sensitivity, and increased local body temperature to help block damaged regions of the body from infection or further damage. They act as the body’s natural bandages to keep pathogens out and swell around damaged joints like a natural cast to limit movement. Leukotrienes help the body heal after prostaglandins have taken effect by reducing inflammation while helping white blood cells to move into the region to clean up pathogens and damaged tissues. Physiology of the Endocrine System Endocrine System vs. Nervous System Function The endocrine system works alongside of the nervous system to form the control systems of the body. The nervous system provides a very fast and narrowly targeted system to turn on specific glands and muscles throughout the body. The endocrine system, on the other hand, is much slower acting, but has very widespread, long lasting, and powerful effects.

Hormones are distributed by glands through the bloodstream to the entire body, affecting any cell with a receptor for a particular hormone. Most hormones affect cells in several organs or throughout the entire body, leading to many diverse and powerful responses. Hormone Properties Once hormones have been produced by glands, they are distributed through the body via the bloodstream. As hormones travel through the body, they pass through cells or along the plasma membranes of cells until they encounter a receptor for that particular hormone. Hormones can only affect target cells that have the appropriate receptors. This property of hormones is known as specificity. Hormone specificity explains how each hormone can have specific effects in widespread parts of the body. Many hormones produced by the endocrine system are classified as tropic hormones. A tropic hormone is a hormone that is able to trigger the release of another hormone in another gland. Tropic hormones provide a pathway of control for hormone production as well as a way for glands to be controlled in distant regions of the body. Many of the hormones produced by the pituitary gland, such as TSH, ACTH, and FSH are tropic hormones. Hormonal Regulation The levels of hormones in the body can be regulated by several factors.

The nervous system can control hormone levels through the action of the hypothalamus and its releasing and inhibiting hormones. For example, TRH produced by the hypothalamus stimulates the anterior pituitary to produce TSH. Tropic hormones provide another level of control for the release of hormones. For example, TSH is a tropic hormone that stimulates the thyroid gland to produce T3 and T4. Nutrition can also control the levels of hormones in the body. For example, the thyroid hormones T3 and T4 require 3 or 4 iodine atoms, respectively, to be produced. In people lacking iodine in their diet, they will fail to produce sufficient levels of thyroid hormones to maintain a healthy metabolic rate. Finally, the number of receptors present in cells can be varied by cells in response to hormones. Cells that are exposed to high levels of hormones for extended periods of time can begin to reduce the number of receptors that they produce, leading to reduced hormonal control of the cell. Classes of Hormones Hormones are classified into 2 categories depending on their chemical make-up and solubility: water-soluble and lipid-soluble hormones.

Each of these classes of hormones has specific mechanisms for their function that dictate how they affect their target cells. Water-soluble hormones: Water-soluble hormones include the peptide and amino-acid hormones such as insulin, epinephrine, HGH, and oxytocin. As their name indicates, these hormones are soluble in water. Water-soluble hormones are unable to pass through the phospholipid bilayer of the plasma membrane and are therefore dependent upon receptor molecules on the surface of cells. When a water-soluble hormone binds to a receptor molecule on the surface of a cell, it triggers a reaction inside of the cell. This reaction may change a factor inside of the cell such as the permeability of the membrane or the activation of another molecule. A common reaction is to cause molecules of cyclic adenosine monophosphate (cAMP) to be synthesized from adenosine triphosphate (ATP) present in the cell. cAMP acts as a second messenger within the cell where it binds to a second receptor to change the function of the cell’s physiology.

Lipid-soluble hormones: Lipid-soluble hormones include the steroid hormones such as testosterone, estrogens, glucocorticoids, and mineralocorticoids. Because they are soluble in lipids, these hormones are able to pass directly through the phospholipid bilayer of the plasma membrane and bind directly to receptors inside the cell nucleus. Lipid-soluble hormones are able to directly control the function of a cell from these receptors, often triggering the transcription of particular genes in the DNA to produce "messenger RNAs (mRNAs)" that are used to make proteins that affect the cell’s growth and function. Prepared by Tim Taylor, Anatomy and Physiology Instructor Endocrine Test Review at Glastonbury High School - StudyBlue StudyBlue Last Modified: 2012-02-16 Size: 102 Views: 124 Which of the following systems work closely with the endocrine system to coordinate the body's functions? Nervous system Which of the following is not an endocrine gland? Sebaceous gland Which of the following organs contains hormone producing cells? Stomach, liver and skin A Second messenger in the action of many water soluble hormones such as peptides is...

cAMP Hormones that bind to receptors within the target cells are.... Lipid- Soluble What are the hormones that regulate blood calcium levels? PTH and Calcitonin A hormone that under certain circumstances is regulated by positive feedback is... Oxytocin The pituitary gland is attached to the Hypothalamus by the... Infundibulum Which of the following hormones stimulates testosterone production by the testis? LH Which of the following hormones is released in response to a nerve impulse? Epinephrine All of the following are hormones of the anterior pituitary EXCEPT... Oxytocin The hormone which effects skin pigmentation is.... MSH Which of the following hormones is released in response to Hypoglycemia? GH Insulinlike growth factor is released in response to... human growth hormone All of the following hormones are released in response to releasing hormones EXCEPT Oxytocin Which of the following hormones do neurosecretory cells produce? Antidiuretic hormone Antidiuretic hormone and oxytocin are produced by the... Hypothalamus The hormone which is released in large quantities just prior to childbirth is... Oxytocin Which of the following hormones controls the productions and release of glucocoticoids?

ACTH Calcitonin is a hormone of the.... Thyroid Gland Which of the following cells produce Thyroxine? Follicular Cells The hormone released in response to low blood calcium levels is... Parathyroid Hormone The hormone that inhibits the action of osteoclasts is... Calcitonin Mineralcorticoids... Are produced in the adrenal cortex, are steroid hormones, help regulate the homeostasis of sodium and potassium (All of the above) Glucocorticoids are steroid hormones produced by the... Adrenal gland Which of the following endocrine glands is directly controlled by the autonomic nervous system? Adrenal Medulla Which of the following hormones are responsible for the fight or flight response? Epinepherine and Norepinepherine The gland which can be classified as both an Endocrine and Exocrine gland is the.... Pancreas Cushing's syndrome is due to oversecretion of.... Glucocorticoids A decline in the number of pancreatic beta cells is characteristic for... Type 1 Diabetes Cells that respond to a particular hormone are called.... target cells Hormone secretion is controlled by which of the following?

(all of the above) nerve impulses, circulating chemicals, releasing hormones, inhibiting hormones The activities of the adrenal cortex are controlled by... ACTH Which hormone stimulates cells to grow and divide? Growth hormone Glucagon is produced in the ____ cells of the _____. Alpha, pancreas Insulin is secreted by the pancreas after a meal in order to... Decrease the concentration of blood glucose An adult who over secretes GH doesn't get taller. Why not?

Epiphyseal plates are closed in adults Under normal circumstances, individuals do not produce too much thyroxine because: It is under negative feedback control (t/f) The nervous system and the endocrine system regulate homeostasis True (t/f) Hormones do not regulate the activity of the immune system False (t/f) Steroid hormones are derivatives of cholesterol True (t/f) Most peptide and protein hormones diffuse through the phospholipid bilayer to get into a target cell False (t/f) Hormone secretion is primarily regulated by the negative feedback system True (t/f) Cells of the posterior pituitary produce vasopressin False (t/f) Some glands produce hormones in response to a signal from the autonomic nervous system True (t/f) Prolactin is a hormone involved in the initiation of milk production in the mammary glands True (t/f) Hormones of the Hypothalamus control the release of human growth hormone from the anterior pituitary True (t/f) FSH stimulates the testis to produce testosterone False (t/f) Vasopressin is another name for antidiuretic hormone True (t/f) Alcohol inhibits ADH secretion resulting in an increased urine output True (t/f)

 Calcitonin is a hormone of the Parathyroid gland False (t/f) The renin-angiotensin pathway is involved in the control of aldosterone secretion True (t/f) Androgens are hormones secreted by the male endocrine system only False (t/f) Steroid hormones act by binding to a protein receptor on the cell membrane of the ir target cell False (t/f) The Hypothalamus controls secretion of hormones from the anterior pituitary gland by nervous impulses False (t/f) Some glands produce hormones in response to a signal from the autonomic nervous system True (t/f) A player in the NBA would benefit from an injection of GH False (t/f) All of the hormones of the pituitary gland are actually produced there False The science concerned with the endocrine system is called _______.

endocrinology The endocrine system releases messenger molecules called _____ hormones Hormones that pass from secretory cells into interstitial fluid and then into the blood are called _______ hormones. Circulating The hypothalamus controls the activity of the anterior pituitary by way of _____ and _______ hormones releasing and inhibitory hormones The production of Oocytes by the ovaries is stimulated by ________ follicle stimulating hormone (FSH) Calcitriol is a hormone of the _____ kidneys Hormones that can enter the plasma membrane without a receptor are _____-_____ hormones Lipid Soluble The production and secretion of thyroid hormone is stimulated by _____ _____ hormone. Thyroid Stimulating Hormone (TSH) The formation of corpus Luteum is stimulated by the _______ hormone.

Lutinizing hormone (LH) The release of milk by the mammary glands depends on the hormone _____ oxytocin The receptors in the hypothalamus that detect low water concentration in the blood are _________ Osmoreceptors The inhibition of bone breakdown is the function of _______ Calcitonin Oxyphl cells are found in the _______ gland parathyroid The class of adrenal cortex hormones that deals with the metabolism and resistance to stress are _______ Glucocorticoids Mineralcorticoids are produced in the ____ _______ adrenal cortex The two principal hormones of the adrenal medulla are _____ and _____ Epinepherine and Norepinepherine The endocrine portion of the pancreas consists of clusters of cells called ______ pancreatic islets The conversion of glucose into glycogen is accelerated by ___ insulin Over secretion of hGH during childhood results in ____ giantism An enlarged thyroid gland is called _____ goiter Hormones that influence other endocrine glands are called _____ hormones Tropic Oxytocin and antidiuretic hormones are produced in cells of the _____ hypothalamus Thyroid hormones regulate growth and development, the activity of the nervous system, and ______ metabolism The adrenal gland is composed of the adrenal medulla and the ____ _____ adrenal cortex

Question: What is produced by the cortex of supra-renal glands that stimulates the autonomic nervous system?
Answer: Adrenalin