7.20.F - Quiz: The Endocrine System

Choose the two systems responsible for coordinating and directing body functions.

-Endocrine system and -Nervous system

Which two endocrine glands are located in the brain?

-Pituitary gland and -Pineal gland

Which two regions does the pituitary gland consist of?

-Posterior lobe AND -Anterior lobe

Which three characteristic(s) belong only to endocrine glands?

-Target cells located some distance away from the secreting gland -Utilize chemical messengers called hormones -Secrete directly into the intercellular fluid and bloodstream

Choose the two features that apply to endocrine glands.

-Trigger a cellular response at the molecular or genetic level -Control long-term activities of the body

Check all that apply. Which of the following does the thyroid regulate?

1. Body metabolism 2. Blood calcium levels 3. Synthesis of protein

Which TWO hormones work together to maintain blood calcium homeostasis?

1. Calcitonin 2. Parathyroid hormone

Determine the TWO correct statements that apply to the circle labeled letter E.

1. Endocrine gland stimulated to produce more hormones 2.Control center

Match the bodily change that occurs in fight-or-flight mode with its purpose:

1. Increased heart rate and blood pressure-Delivering glucose, hormones, and oxygen to cells for enhanced energy production 2. Blood flow redistribution-Vasoconstriction/vasodilation shunting blood to skeletal muscles and away from skin, guts, and kidneys 3. Increased sweat production-Regulating body temperature

Determine the TWO correct statements that apply to the diagram.

1. Letter A indicates receptors that sense a hyperhormonal level. 2. Letter F indicates the increase of hormonal secretion to return levels to homeostasis.

Choose the name AND the function of the structure indicated by the letter B. (You will pick TWO answers.)

1. Responds to hormone 2. Target cell

Which statements do NOT refer to type 2 diabetes? Choose all that apply.

1. Sudden onset 2. Ketoacidosis is common

Which TWO of the following functions are triggered by the release of adrenaline?

1.Dilation of the bronchioles in the lungs 2.. Increased heart rate and blood pressure

Which TWO functions does the hormone melatonin regulate?

1.Inhibiting the secretion of gonadotropins 2.Maintaining circadian rhythms

During long-term stress situations, these TWO organs regulate cortisol release.

1.Pituitary gland and 2.Hypothalamus

The Parathyroid Glands Tiny masses of glandular tissue, the parathyroid glands, are located on the thyroid gland's posterior surface. Typically, there are two glands located within each thyroid lobe, but the exact location and number may vary. The four green shaded areas represent the most common position of the parathyroid glands, which are generally four in number and situated behind the lateral lobes of the thyroid gland (shaded orange).

Actions of the Thyroid Hormone Every cell in the body is a target since the thyroid hormone controls the rate at which glucose is converted to chemical energy. The calorgenic, or heat-producing, effect of this hormone results from the increased oxidation of glucose, thus increasing the body's metabolic rate and body heat production. TH is also critical for regulating tissue growth and development, especially in the reproductive and nervous systems. The body's metabolism, the rate of the body's use of energy, synthesis of proteins, and sensitivity to other hormones are all affected by the thyroid hormone. The hormonal output from the thyroid is regulated by thyroid-stimulating hormone (TSH) produced by the anterior pituitary, which itself is regulated by thyrotropin-releasing hormone (TRH) produced by the hypothalamus. The thyroid hormone also provides negative feedback to the hypothalamus and anterior pituitary gland. Elevated thyroid hormone in the blood leads to a reduction in TSH production and TRH production, and vice versa.

Which one of the following is incorrectly matched?

Adrenal cortex - chromaffin cells

These glands affect sex hormone levels, metabolism, kidney function, and the fight-or-flight response.

Adrenal glands

These glands atop your kidneys are responsible for regulating the body's response to stressors such as danger, sports, and the like.

Adrenal glands

This structure is part of the sympathetic nervous system and is more like a knot of nervous tissue than a gland.

Adrenal medulla

Which hormone regulates the electrolyte concentrations in extracellular fluids, particularly Na+ and K+ ions?

Aldosterone

Neurosecretory cell stimulation causes which of the following to occur?

An action potential that initiates the release of the stored hormones into the systemic blood circulation

Which hormone increases the reabsorption of water and inhibits urine production?

Antidiuretic hormone

The Anterior Pituitary Gland and the Hypothalamus The anterior pituitary produces hormones that regulate other endocrine glands. Specialized neurons within the hypothalamus, called neurosecretory cells, release hormones to control the anterior pituitary's secretions. This results in communication between the two glands. These hypothalamic hormones are called releasing hormones and inhibiting hormones, depending on their influence on the anterior pituitary gland. The hypothalamic hormones are secreted into the hypothalamic-hypophyseal portal system of capillaries, which supplies the anterior pituitary. The hormones then diffuse into the anterior pituitary, initiating the production of specific hormones.

Antidiuretic hormone (ADH, also known as vasopressin) stimulates the kidney's collecting ducts to aid in the blood's reabsorption of water. This inhibits urine production as needed to maintain the body's water balance, preventing dehydration or water overload. Drinking large amounts of water or drinking alcoholic beverages inhibits ADH release resulting in increased urine output. Vast amounts of ADH are released under extreme conditions, such as excessive blood loss. In this situation, the ADH targets the smooth muscles of the blood vessels. The resulting vasoconstriction raises the blood pressure to maintain the vital organs. Hyposecretion of ADH can lead to diabetes insipidus, marked by huge urine output and intense thirst. This condition may result from a malfunctioning hypothalamus or posterior pituitary lobe. Hypersecretion of ADH can result in SIADH, syndrome of inappropriate ADH secretion. This condition may result from meningitis, hypothalamic surgery, or lung cancer and is characterized by brain edema, weight gain due to fluid retention, and decreased solute concentration in the blood.

What Is Diabetes? Diabetes mellitus is a term for several conditions that affect how the body turns food into energy. The body does not use insulin as it should, so too much glucose stays in the blood, resulting in a condition called high blood sugar (hyperglycemia). Hyperglycemia can damage the vessels that supply blood to vital organs, increasing the risk of heart disease and stroke, kidney disease, vision problems, and nerve problems. This can cause health problems that may be serious or even life-threatening. With treatment and lifestyle changes, people with diabetes can live long, healthy lives, but there is no cure for diabetes.

Blood Glucose Regulation Regulation of blood glucose is the responsibility of the pancreas' endocrine hormones. The balance of hormones is achieved through a negative feedback loop. As a meal containing carbohydrates is eaten and digested, blood glucose levels rise, and the pancreas turns on insulin production and turns off glucagon production. Glucose from the bloodstream enters liver cells, in which glucose is converted to chains of glycogen for storage as long as both insulin and glucose remain plentiful. After a meal has been digested and blood glucose levels begin to fall, insulin secretion drops, and glycogen synthesis stops. When it is needed for energy, glucagon stimulates the liver to break down glycogen into glucose for easy transport through the bloodstream to the body's cells.

Which one of the following is NOT regulated by the endocrine system?

Body temperature

The reproductive glands and their hormones will be discussed in detail in the Reproductive System Lessons.

Calcitonin Calcitonin, a hormone that regulates blood calcium levels, is also produced by the thyroid. PTH and calcitonin (produced by the thyroid) work together to maintain calcium homeostasis. The secretion of calcitonin is determined by the calcium level in the blood, as indicated at the top of the graphic shown to the left. When levels of calcium in the blood increase (hypercalcemia), calcitonin is secreted in higher quantities. When calcium levels in the blood decrease (hypocalcemia), this causes the amount of calcitonin secreted to decrease. Calcitonin decreases blood calcium levels through the stimulation of osteoblasts, which deposit bone, causing calcium removal from the blood.

Mechanism of Action Receptors for lipid-soluble steroid hormones are inside the target cells because lipid-soluble hormones can diffuse across the phospholipid bilayer of the plasma membrane and directly enter the cell. In turn, this means that these types of hormones can initiate a response through a process called Direct Gene Activation.

Categories of Hormones The power of the endocrine system lies in the hormones it synthesizes and secretes due to the impact these have on specific cells of the body. These chemical messengers regulate the metabolic activity of all other body cells. Many different hormones are produced, but almost all of them can be chemically classified into the following categories: Nonsteroidal hormones such as amines, peptides, glycoproteins, and proteins from various glands in the body. Steroid hormones are synthesized from cholesterol in the adrenal glands, the reproductive glands (gonads), and the placenta. Eicosanoids are not really hormones; these are biologically active lipids found in cell membranes. They function locally and impact nearby cells, so they do not fit the definition of "true hormones."

Which term includes all the other terms?

Corticosteroids

Which hormone regulates the energy metabolism of most body cells and help resist stressors?

Cortisol

Place the listed steps of the Direct Gene Activation mechanism in the order they occur. The synthesized protein produces the steroid hormone's desired effects. The steroid hormone diffuses through the cell membrane to enter the cytoplasm. Depending on the intracellular receptor location, the hormone may need to diffuse through the nuclear membrane to enter the nucleus. The hormone then binds to its specific intracellular receptor protein to form a hormone-receptor complex. The endocrine gland secretes the steroid hormone. The hormone is carried in the bloodstream throughout the body. Steroid hormone-receptor complex will bind to specific sites on the DNA, which initiates transcription of mRNA. This is the first step of protein synthesis. mRNA enters the cytoplasm to direct translation, the second step of protein synthesis.

D, B, C, E, F, A

Features of Nonsteroidal Hormones Most hormones are nonsteroidal and vary greatly in molecular size. Nonsteroidal hormones can be split into three groups based on their size—simple amino acid derivatives, peptides, and proteins. Their names often end with -in (oxytocin or insulin) or -ine (norepinephrine or epinephrine.) Peptide hormones are synthesized in the rough endoplasmic reticulum, transferred to the Golgi apparatus, and packaged into secretory vesicles for export to where they are needed. They are stored in the endocrine cell until signals are received that they should be secreted. Typically, these hormones do not have the lasting effects of lipid-soluble types because they have a shorter half-life and rapid action. Since they freely travel in the blood plasma, they can easily be excreted by the kidneys.

Direct Gene Activation Read through the sequence of steps of Direct Gene Activation. It is aptly named since steroid hormones impact the genes in the cell nucleus directly. The endocrine gland secretes the steroid hormone. The hormone is carried in the bloodstream throughout the body. The steroid hormone diffuses through the cell membrane to enter the cytoplasm. Depending on the intracellular receptor location, the hormone may need to diffuse through the nuclear membrane to enter the nucleus. The hormone then binds to its specific intracellular receptor protein to form a hormone-receptor complex. The steroid hormone-receptor complex will bind to specific sites on the DNA, which initiates the transcription of mRNA. This is the first step of protein synthesis. Messenger RNA (mRNA) enters the cytoplasm to direct translation, the second step of protein synthesis. The synthesized protein produces the steroid hormone's desired effects.

How Hormones Work All hormones circulate in the bloodstream, but they must locate the target cells that they need to influence in order to have an effect. Target cells are the tissue cells that have a specific receptor for a particular hormone and that are altered by the hormone when they meet. These receptors may be inside the cell (intracellular) or on the surface of the cell (extracellular) depending on the type of hormone. Hormones cause effects by altering target cell activity, by either increasing or decreasing the rates of the cell's metabolic processes.

Endocrine vs. Nervous System The endocrine system and the nervous system work together in coordinating and directing body functions. However, they work in very different ways. Observe these feature differences in the chart below. Some of the endocrine glands are also part of the nervous system. This overlap allows the two systems to interact and integrate their responses. The endocrine system response is relatively slower than the response of the nervous system due to the multiple steps of the process. First, endocrine hormones must be synthesized. Second, they must be transported to their target cell through the bloodstream. Third, the hormones must enter the target cell. The hormones are slower to react when compared to a nerve impulse, but their effects last even after the stimulus is removed, unlike a nerve impulse.

Which phase/stage occurs when prolonged exposure to the stressor depletes the body's resources?

Exhaustion

Glucagon balances the action of the two opposing hormones, insulin and somatostatin.

FALSE

The pancreas has two main functions: an endocrine function that helps in digestion, and an exocrine function that regulates blood sugar.

FALSE

Which TWO hormones affect reproductive functions?

FSH and LH

An Exception to Every Rule It seems that there is an exception to every rule! Typically, all lipid-soluble hormones are derived from steroids, BUT there is one exception: thyroid hormones are the only lipid-soluble nonsteroid hormones. Even though they are not derived from steroids or cholesterol, thyroid hormones are soluble in lipids, they also use a direct gene activation mechanism.

Features of Steroid Hormones Steroid hormones include the sex hormones made by the ovaries and testes, the thyroid hormones, and the hormones produced by the adrenal cortex. These hormones are synthesized on the smooth endoplasmic reticulum membranes and immediately released from the endocrine cell after synthesis. Derived from cholesterol - which is a steroid - steroid hormones are lipid-soluble substances. (Remember from your early study of biology that steroids are a type of lipid.) This means that they cannot float freely along in the bloodstream, but must be bound to proteins in the plasma in order to travel. Then, they must bind to proteins on the cell membrane in order to enter into the target cell. Finally, these types of hormones bind to intracellular receptors in the cytoplasm to activate genes inside the nucleus and initiate the synthesis of a particular type of protein necessary for metabolism or body functioning. Steroid or lipid-soluble hormones are long-lasting because they have a slower action and a longer half-life in the body. They also must be metabolized by the liver when they are done working because they are bound to plasma proteins, and can't just be filtered out of the bloodstream by the kidneys. Steroid hormones can be split into five groups based on the type of receptors they bind to: glucocorticoids, mineralocorticoids, androgens, estrogens, and progestogens. Their names usually end in -ol or -one, including cortisol, estradiol, testosterone, and aldosterone. Steroid hormones help regulate metabolism, inflammation, immune functions, ion and water balance, and the sexual characteristics.

The anterior pituitary, a.k.a. adenohypophysis, is considered a primary glandular organ of the endocrine system. Processes such as stress, growth, reproduction, and lactation are all regulated by the anterior pituitary under the hypothalamus's control. The major hormones secreted by the Anterior Pituitary Gland are: ACTH (adrenocorticotropic hormone)- ACTH targets the adrenal cortex to release glucocorticoids, mineralocorticoids, and androgens. Hyposecretion is rare, while hypersecretion can lead to Cushing's disease.

GH (growth hormone)- Growth hormone, also known as somatotropin, is an anabolic hormone that has metabolic and growth-promoting actions. Although GH stimulates most body cells to grow and divide, its major target organs are bones and skeletal muscles. Hyposecretion leads to pituitary dwarfism (shown on the left), and hypersecretion leads to gigantism (shown on the right). LH (luteinizing hormone)- LH regulates the hormonal activity of the gonads (testes and ovaries). In men, it promotes testosterone production. In women, it triggers ovulation and stimulates ovarian production of estrogen and progesterone. Hyposecretion can lead to failure of maturation in both sexes. Hypersecretion has no significant effects. FSH (follicle stimulating hormone)- FSH regulates the gamete (sex cell) production of the gonads (testes and ovaries). In men, it stimulates sperm production. In women, ovarian follicle maturation occurs. Hyposecretion can lead to failure of maturation in both sexes. Hypersecretion has no significant effects. TSH (thyroid stimulating hormone)- TSH influences the growth and activity of the thyroid gland and stimulates the release of thyroid hormones. Hyposecretion may result in hypothyroidism leading to myxedema. Hypersecretion may result in hyperthyroidism with effects similar to Graves' disease. PRL (prolactin)- PRL is similar to growth hormone, but its only known target is breast tissue. After childbirth, it stimulates and maintains milk production (lactation). Hyposecretion may cause poor milk production in nursing women. Hyposecretion may cause galactorrhea (inappropriate milk production in men or women). Impotence in males and cessation of menses in females may also occur.

Take a look at the five releasing hormones of the hypothalamus:

GHRH (growth hormone-releasing hormone)- GHRH targets the anterior pituitary and stimulates it to increase growth hormone (GH) secretion. CRH (corticotropin-releasing hormone)- CRH targets the anterior pituitary and stimulates it to increase adrenocorticotropic hormone (ACTH) secretion. GnRH (gonadotropin releasing hormone)- GnRH targets the anterior pituitary and stimulates it to increase luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion. TRH (thyroid-releasing hormone)- TRH targets the anterior pituitary and stimulates it to increase thyroid-stimulating hormone (TSH) secretion. PRH (prolactin-inhibiting hormone)- PRH targets the anterior pituitary and stimulates it to increase prolactin (PRL) secretion.

Which pancreatic hormone stimulates glycogen's breakdown in the liver to glucose?

Glucagon

An enlarged, protruding yet nonfunctional thyroid gland known as what?

Goiter

This is the medical term for an enlarged thyroid.

Goiter

Which statement does NOT refer to type 1 diabetes?

Gradual onset

Which of the following is NOT a symptom of hypothyroidism?

Graves' disease

Which one of the following does NOT apply to the endocrine system?

Has specific localized effects

Chemical messengers that regulate the metabolic activity of all other body cells are known as what?

Hormones

General Symptoms of Diabetes Mellitus Symptoms of diabetes can be similar in type 1 diabetes, typically diagnosed in children and teens, and type 2 diabetes, which most often occurs in adults. Symptoms of any diabetes are related to high blood and urine glucose levels and include frequent urination (polyuria), nausea, vomiting, blurred vision, weight loss or gain and extreme hunger (polyphagia), dehydration and extreme thirst (polydipsia), fatigue, dry mouth, slow-healing wounds, cuts, or sores, itching skin, and increased susceptibility to infections.

Hormones of the Pancreas The Islets of Langerhans produce three hormones—insulin, glucagon, and somatostatin—from three different kinds of cells, called beta, alpha, and delta cells, respectively. Glucagon is secreted from alpha cells and stimulates glycogen's breakdown in the liver to glucose; thus, it raises sugar levels in the blood. Insulin is secreted from beta cells and enables the cells to absorb glucose and use it or convert it into glycogen. This promotes glucose utilization by the body cells and stimulates the deposition of extra glucose of the blood as glycogen in the liver and skeletal muscles. Somatostatin is secreted from delta cells and balances the secretion of insulin and glucagon. It helps the pancreas alternate in turning on or turning off each opposing hormone.

Hormonal control refers to the release of hormones in response to other hormones released by the hypothalamus. This is the most common type of stimulus. For example, when your metabolism needs a boost, the hypothalamus will release thyrotropin-releasing hormone (TRH) to cause the anterior pituitary to release thyroid-stimulating hormone (TSH), which targets cells in the thyroid, resulting in the secretion and release of T3 and T4. Neural control refers to the release of hormones in response to neural stimulation. The most obvious example is the stress response. Your sympathetic nervous system will signal the adrenal medulla cells, causing the release of adrenaline, the fight-or-flight hormone.

Humoral control refers to the release of hormones in response to altered blood levels of certain critical ions or nutrients. For example, the level of blood glucose rises when you eat. This triggers the pancreas to release insulin, which causes the target cells to take in the glucose, thus lowering your blood sugar back to normal levels. The cells will then use this glucose to make ATP, the body's energy molecule.

When does the sympathetic nervous system activate the fight-or-flight response?

In short-term stress situations

Which hormone is correctly matched to the cell type that it is secreted by?

Insulin - beta cells

This is a simplified diagram of the Second Messenger System Activation mechanism. Which one of the following molecules is NOT a part of this system?

Intracellular receptor protein

The endocrine cells of the pancreas that produce and secrete the hormones insulin and glucagon into the bloodstream are located where?

Islets of Langerhans

Which characteristic only applies to a steroid hormone?

Lipid soluble

The pineal gland is a small endocrine gland located behind the third ventricle on the brain's midline (between the two cerebral hemispheres). Its name refers to its small pinecone shape (Latin, pinea). The pineal gland's main function is to receive information about the amount of light present in the environment and to secrete the hormone melatonin.

Melatonin The hormone melatonin (not to be confused with the pigment melanin) is the only hormone secreted in significant amounts by the pineal gland. This hormone's secretion is dictated by light exposure relayed to the pineal gland by the eyes. Often called the "sleep trigger," its peak levels occur at night and make us drowsy, while lower levels occur during the day to keep us alert. The hormone's primary target organ is the brain's suprachiasmatic nuclei, a tiny region located in the hypothalamus. It is the central regulator of most circadian rhythms in the body. Melatonin is also thought to target the anterior pituitary and affect the secretion of reproductive hormones. So, melatonin has two primary functions in humans: Maintaining circadian rhythms. Regulating reproductive hormones by inhibiting the secretion of gonadotropins (luteinizing hormone and follicle-stimulating hormone) from the anterior pituitary gland.

Which organ consists of hypothalamic tissue that grows downward?

Neurohypophysis

Functions of the Endocrine System The endocrine system consists of several organs and glands that regulate body processes, including: the regulation of cellular metabolism and energy balance, the maintenance of electrolyte, water, and nutrient balance of the blood, the mobilization of the body defenses, and the regulation of reproduction, growth, and development.

Organs of the endocrine system include the pituitary gland, the pineal gland, the thyroid gland, the parathyroid glands, the adrenal glands, the pancreas, and the reproductive glands (testes and ovaries). Endocrine Glands vs. Exocrine Glands Endocrine glands are ductless glands of internal secretions. Chemical messengers called hormones are released directly into the bloodstream. The hormones utilize the bloodstream and intercellular fluid to travel to the target cells, which may be located some distance away from the secreting gland. When the hormones reach the target cells, they will trigger a cellular response at a molecular protein level or a genetic level to control the ongoing or long-term activities of the body. In contrast, exocrine glands are glands of external secretions. Chemical regulators called enzymes are released through a duct or canal to the target cells, which are located very close to the gland. These secretions are carried directly to the site of action (located on the body's surface or in another organ) to create a rapid response to control short-term activities of the body. Exocrine examples include the gastric glands, the sweat glands, the mammary glands, and the lacrimal glands. Exocrine glands are not part of the endocrine system.

The Hypothalamus The hypothalamus, which is part of the nervous system, is also recognized as a major endocrine organ because it produces several hormones. Its main job is to tell the anterior pituitary gland to start or stop making hormones.

Overview of the Pituitary-Hypothalamic Relationships One of the most important hypothalamus functions is to link the nervous system to the endocrine system via the pituitary gland (aka. hypophysis). The pituitary gland consists of two major lobes, the anterior pituitary and the posterior pituitary. The pituitary gland is your endocrine system's master gland. It uses the information it gets from the hypothalamus to tell other glands in your body what to do. It extends from the bottom of the hypothalamus and resides in a small, bony cavity in the skull known as the sella turcica. The infundibulum is the hollow stalk connecting the hypothalamus to the posterior pituitary lobe via the hypothalamic-hypophyseal tract and the anterior pituitary lobe via the hypothalamic-hypophyseal portal system. The hypothalamus controls the release of hormones from the pituitary gland using these two mechanisms.

This is the hormone that acts to increase blood calcium levels through osteoclasts' stimulation, which breaks down the bone, causing a release of calcium into the blood.

PTH

Humans typically have 4 of these glands in their body.

Parathyroid glands

Which general symptom of diabetes mellitus is NOT correctly matched to its description?

Polydipsia - frequent dry mouth

Which organ stores hormones rather than producing them?

Posterior pituitary gland

Which type of diabetes do more than a third of people in the United States have, but most don't know it?

Prediabetes

Which one of the following is NOT a function of the endocrine system?

Providing for sensation, higher mental functioning, and emotional response

Mechanism of Action This hormone category will interact with receptors on the target cell surface. Because they are water-soluble substances they can be transported freely in the blood plasma, but they cannot diffuse through the cell membranes when they arrive at their destination. Instead, they must bind to extracellular receptors on the cell membrane. When they bind, it alerts a second messenger molecule inside the cell that activates enzymes and other cellular proteins or influences gene expression.

Secondary Messenger System Activation 1. The hormone (called an agonist), acting as the first messenger, binds to the extracellular receptor on the target cell membrane. 2 The hormone-receptor complex changes shape and activates the G-protein inside the cell. 3. The activated G protein then binds to an enzyme (adenylate cyclase) called an effector. 4. This complex of G protein and adenylate cyclase then converts ATP to cyclic AMP (cAMP), the second messenger. 5. The cAMP freely diffuses throughout the target cell, activating the protein kinases. The activated protein kinases trigger the response of the target cell. Secondary Messaging involves a series of steps inside the cell to cause the desired effect of the water-soluble hormone.

Which is the correct order of synthesis and release in the regulation of thyroid hormonal output?

TRH, TSH, T3 & T4

Alpha cells of the pancreas release glucagon into the blood in response to hypoglycemia.

TRUE

Which one of the following applies only to the nervous system?

Target cells include muscle cells and glandular cells

What Is Stress? Stress is a bodywide nonspecific response to actual or potential threats to homeostasis. The hypothalamus coordinates this response in both short-term and long-term situations to maintain normal function despite stressors. A stressor is any factor that creates a significant change in the body's internal or external environment. The General Stress Response (GSR) is also known as the General Adaptation Response (GAR) or the General Adaptation Syndrome (GAS). The Three Stages of Stress The general adaptation syndrome (GAS), developed by Hans Selye, describes the pattern of responses that the body goes through after being prompted by a stressor. There are three stages: alarm, resistance, and exhaustion.

The Adrenal Medulla The core of the adrenal glands is the adrenal medulla, which is surrounded by the adrenal cortex. The inner medulla is part of the sympathetic nervous system and is more like a knot of nervous tissue than a gland. The medullary chromaffin cells are modified sympathetic neurons within the medulla that synthesize the catecholamines. Upon receiving sympathetic stimulation, these neuroendocrine cells will release adrenaline and noradrenaline into the bloodstream. These hormones are water-soluble and are the most important hormones of the fight-or-flight response. The secretions of the adrenal medulla are 20% noradrenaline (norepinephrine) and 80% adrenaline (epinephrine). With few exceptions, these two hormones exert the same effects, including: Increased heart rate and blood pressure Blood vessel constriction in the skin and gastrointestinal tract Smooth muscle dilation Dilating bronchioles and capillaries Increased metabolism The catecholamine receptors are found throughout the body, allowing for a system-wide response following release.

Prediabetes Prediabetes is when the blood sugar is consistently higher than it should be, but not high enough for a diagnosis of diabetes. More than a third of people in the United States have prediabetes, but most do not know it. Prediabetes can typically be addressed through diet modifications, exercise, and lifestyle changes; however, some cases do require medication.

The Pancreas The pancreas is about 6 inches long and sits across the back of the abdomen, behind the stomach. The head of the pancreas is toward the right side of the abdomen, close to the midline. The pancreatic duct connects it to the duodenum (the first section of the small intestine). The narrow end of the pancreas, called the tail, extends to the body's left side. The pancreas has two main functions: an exocrine function that helps in digestion and an endocrine function that regulates blood sugar. The islets of Langerhans are the endocrine cells of the pancreas that produce and secrete the hormones insulin and glucagon into the bloodstream. Acinar cells are the exocrine cells of the pancreas that produce and transport enzymes that assist in the digestion of food.

Oxytocin is released during childbirth, stimulating the uterine muscles to cause increasingly strong labor contractions. It also acts on the mammary gland tissue to initiate milk ejection. The effects of hypo- or hypersecretion are unknown. Both of these processes result from a positive feedback mechanism. For example: 1. In childbirth, the head of the baby pushes against the cervix. 2. This stimulates a nerve impulse from the cervix to the brain. 3. The hypothalamus signals the posterior pituitary gland to release oxytocin. 4. Oxytocin is carried in the bloodstream to the uterus. 5. This causes contractions, pushing the baby towards the cervix. This positive feedback mechanism continues until the baby is born.

The Posterior Pituitary Gland and Hypothalamic Hormones The posterior pituitary, a.k.a. the neurohypophysis is derived from hypothalamic tissue that grows downward. A bundle of axons called the hypothalamic-hypophyseal tract runs through the infundibulum, maintaining a neural connection between the hypothalamus and the posterior pituitary. The hypothalamus communicates with the posterior pituitary using the neurosecretory cells of the hypothalamic-hypophyseal tract. These cells produce two hormones that are transported through the axons in vesicles and stored in the axon terminals embedded in the posterior pituitary. Neurosecretory cell stimulation causes an action potential that initiates the release of the stored hormones into the systemic blood circulation. The neurohypophysis stores hormones rather than producing them and is, therefore, a hormone-storage area and not a true endocrine gland.

Response to Stress In short-term stress situations, the sympathetic nervous system activates the fight-or-flight response. This response stimulates the adrenal medulla to release the catecholamines, which dedicate energy to more relevant bodily systems as an acute adaptation to stress. Once the stress is over, the parasympathetic nervous system returns the body to homeostasis. In long-term stress situations, the hypothalamus and pituitary gland regulate cortisol release, which influences many bodily functions such as metabolic, psychological, and immunological.

The alarm stage: Initiated by the hypothalamus, the body activates physiological changes that ready it for fight or flight in response to a perceived threat or danger. These changes will occur in the body regardless of whether the perceived stressor is considered eustress (positive or pleasant) or distress (negative or unpleasant). Here are a few examples of such bodily changes and their purposes: Increased heart rate and blood pressure: increased circulation delivers glucose, hormones, and oxygen to cells for enhanced energy production Increased levels of blood glucose, fatty acids, and glycerol: provides materials for enhanced energy production Increased respiration rate and dilation of bronchioles: increases oxygen intake for energy production Blood flow redistribution occurs: vasoconstriction/vasodilation shunts blood to skeletal muscles and away from skin, guts, and kidneys Dilation of pupils: increases light entry for enhanced vision Increased sweat production: regulates body temperature, which rises due to increased muscular activity and glucose metabolism

The restiance stage: (stress) If the perceived stress continues, the body stays activated at a higher metabolic level in an effort to offset the persistent stress. The body cannot maintain this level indefinitely, and its resources will eventually deplete. Here are a few examples of such bodily changes and their purposes: Stronger sympathetic nervous system effect on the cardiovascular system Decrease in nonessential energy-using activities such as:Reproduction functions, bone formation, blood cell production, and production of other hormones Long-term elevated hormone levelsIncreased corticotropin-releasing hormone (CRH) leads to increased adrenocorticotropic hormone (ACTH).This causes increased cortisol to alter glucose, fat, and protein metabolism to spare glucose for the brain's use.Increased cortisol suppresses inflammatory and immune responses and diverts energy metabolism from tissue maintenance.

The exhaustion stage: Prolonged exposure to the stressor will deplete the body's resources, and the resulting wear and tear will suppress the immune system and cause bodily functions to deteriorate. This can lead to various health issues and illnesses, including heart disease, digestive problems, depression, diabetes, and death. The return to homeostasis may not be possible if: Stressors are extremely severe Multiple stressors exist Pathologic conditions exist Inappropriate behaviors may delay return to homeostasis If the original stressor remains, this can: Prevent an appropriate response to additional stressors Lessen coping abilities Disrupt memory and intellect

The primary means of regulating the levels of hormones in the bloodstream is through negative feedback mechanisms. Remember that negative feedback occurs when the body senses that a particular substance is too high, or something is occurring too often. Signals are sent to reduce the production of the substance or decrease the frequency of the occurrence. A common example of negative feedback is the management of blood glucose levels. When the body senses the increase in blood glucose after a meal, the pancreas released insulin which causes the cells to allow glucose to enter, thereby reducing the levels in the bloodstream and moving the glucose to where it is used to make energy.

The graphic below illustrates how negative feedback can compensate for rising or falling levels of a hormone needed in the body. In each case, the control centers respond to the messages received from the receptors and order the effectors to take appropriate action A few hormones, such as those involved in the reproductive system and blood clotting, use positive feedback mechanisms. In these cases, the body senses that a substance has been secreted or a series of events has begun. This in turn increases or magnifies the response to the event, causing the process to move forward. For example, when a mother is in labor, stretching of the uterine walls will cause the increased release of oxytocin. This hormone encourages uterine contractions and speeds labor to its conclusion. Type of Stimuli Endocrine glands are regulated in three different ways: hormonal control, neural control, and humoral control. These hormonal negative feedback mechanisms prompt a gland to secrete or inhibit a hormone.

Circadian Rhythms Circadian rhythms are physical, mental, and behavioral changes that follow a 24-hour cycle and can influence our bodies' important functions, such as hormone release, eating habits, body temperature, and digestion. Most people notice the effect of circadian rhythms on their sleep patterns. These rhythms respond primarily to the amount of light you are exposed to, which is why your circadian rhythm typically coincides with the sun's cycle. Darkness stimulates the pineal gland to start producing melatonin, while light causes that production to stop.

The thymus gland is a small gland comprised of two identically sized lobes, located behind the sternum but in front of the heart. It plays an important function both in the immune system and endocrine system. Relatively large in infants, it grows until puberty. In adulthood, it starts to shrink and become slowly replaced by fat. The shrinking is due to the reduced immune system role of the thymus in adulthood. The immune system produces most of its T cells during childhood and requires very few new T cells after puberty. Thymosin The thymus produces and secretes thymosin, a hormone necessary for T-cell, a.k.a. T-lymphocyte development and production. T-cells, a type of white blood cell, originate in the bone marrow and migrate to the thymus gland to mature.

The Adrenal Cortex The adrenal cortex is composed of glandular tissue comprising the bulk of the organ. The cortical layers are arranged in three zones or layers. The cortex synthesizes over two dozen steroid hormones collectively called corticosteroids. These steroid hormones are not stored in the cells, so the rate of synthesis determines their rate of release. All steroid hormones are derived from cholesterol

This middle layer is responsible for producing glucocorticoids, primarily cortisol in humans. Glucocorticoids regulate the energy metabolism of most body cells and help resist stressors. Cortisol, like all steroid hormones, acts on target cells by modifying gene activity. Negative feedback regulates cortisol secretion. This innermost layer has a netlike arrangement and produces a small amount of gonadocorticoids (androgens), the adrenal sex hormones. The main ones being dehydroepiandrosterone (DHEA), DHEA sulfate (DHEA-S), and androstenedione (which is the forerunner to testosterone). The amount produced by the cortex is insignificant compared with the amounts made by the gonads during later puberty and adulthood. They contribute to axillary and pubic hair development and account for the estrogen produced after menopause when the ovaries stop production. The control of their secretion is not completely understood. There is some overlap in function with the zona fasciculata.

The Adrenal Glands The endocrine glands that sit on top of the kidneys are known as the adrenal glands, or the suprarenal glands. They are enclosed by a fibrous capsule and a cushion of fat. Each adrenal gland is structurally and functionally two endocrine glands: the inner adrenal medulla and the outer adrenal cortex. Adrenal glands produce hormones that help regulate your metabolism, immune system, blood pressure, response to stress, and other essential functions. The cortex mainly produces mineralocorticoids, glucocorticoids, and gonadocorticoids, while the medulla chiefly produces the catecholamines: adrenaline and noradrenaline.

This superficial layer produces the mineralocorticoids, mainly aldosterone. The essential function is to regulate the electrolyte concentrations in extracellular fluids, particularly Na+ and K+ ions. K+ ion concentration is critical to all cells' resting membrane potential and determines how easily action potentials can be generated in muscle and nerve cells. Changes in Na+ concentration lead to changes in blood volume and blood pressure. Aldosterone reduces Na+ secretion from the body by stimulating the kidney tubules to reabsorb sodium, increasing blood volume and blood pressure. It also causes K+ secretion into the tubules for elimination from the body via urine.

Which of the following is NOT a reproductive hormone?

Thymosin

The Thyroid Gland One of the largest endocrine glands is the thyroid. It is located on the neck's anterior aspect, below the thyroid cartilage that forms the laryngeal prominence, or Adam's apple. The thyroid gland is constructed of two lobes connected by the isthmus, giving the thyroid a butterfly-like shape.

Thyroid Hormone: T3 and T4 The thyroid hormone, often referred to as the body's major metabolic hormone, is actually two active iodine-containing hormones. The thyroid gland takes iodine, found in many foods, and converts it into thyroid hormones: thyroxine (T4) and triiodothyronine (T3). Thyroid cells are the only cells in the body that can absorb iodine. This means that a deficiency of iodine in the diet will cause the thyroid to be incapable of making thyroid hormones. Triiodothyronine (T3) is the active form of thyroid hormone that can readily go into the human body's cells. This means that every cell of the human body has thyroid receptors. Most T3 is formed at the target tissues by the conversion of T4 to T3. The normal thyroid gland produces about 80% T4 and about 20% T3.

Which gland is constructed of two lobes connected by the isthmus and located below the Adam's apple?

Thyroid gland

Gestational Diabetes Pregnancy usually causes some form of insulin resistance during middle or late pregnancy. Because a woman's blood sugars travel through her placenta to the baby, it is important to control gestational diabetes to protect the baby's growth and development. A baby might have unusual weight gain before birth, trouble breathing at birth, or a higher risk of obesity and diabetes later in life. The mother might need a Caesarean section because of an overly large baby, or they might have damage to their heart, kidney, nerves, and eyes. Gestational diabetes usually resolves after birth.

Type 1 Diabetes Type 1 diabetes is also called insulin-dependent diabetes (IDD). It used to be called juvenile-onset diabetes because it often begins in childhood. Type 1 diabetes is an autoimmune condition occurring when the body attacks the pancreas with antibodies. The organ is damaged and doesn't make insulin. This type of diabetes is thought to involve genetics. Many of the health problems that can come with type 1 diabetes happen because of damage to tiny blood vessels in your eyes (called diabetic retinopathy), nerves (diabetic neuropathy), and kidneys (diabetic nephropathy). People with type 1 diabetes also have a higher risk of heart disease and stroke. Anyone who has type 1 diabetes needs lifelong insulin therapy. Also included in the treatment are monitoring carbohydrate, fat, and protein intake, frequently monitoring blood glucose, and exercising regularly to maintain a healthy weight. The goal is to keep the blood sugar level as close to normal as possible to delay or prevent complications.

People with this type of diabetes need lifelong insulin therapy.

Type 1 diabetes

Insulin Resistance REVIEW: Insulin acts as a key for the glucose to enter the cells to be used for energy. Once this happens, blood sugar levels in the blood are regulated back into a normal range. Insulin resistance is a condition in which the cells fail to respond to insulin. As a result, glucose is unable to enter the cells effectively. The pancreas goes into overdrive and produces more and more insulin to attempt to move the glucose out of the bloodstream and into the cells where it is needed. However, the liver does not react to the usual insulin signal, so it manufactures and secretes more glucose than is needed, resulting in hyperglycemia. Physical inactivity and obesity increase insulin resistance, causing the pancreas to work harder to make more insulin. Unfortunately, it is still not enough to keep the blood sugar levels where they should be.

Type 2 Diabetes Type 2 diabetes is also called non-insulin-dependent (NIDD) or adult-onset diabetes. However, it is becoming more common in children and teens, largely because more young people are overweight or obese. About 90% of people with diabetes have type 2. There are two common causes of type 2 diabetes. The pancreas creates some insulin but not a sufficient quantity. The body cells develop a decreased response to insulin, known as insulin resistance. Type 2 diabetes is often milder than type 1. But it can still cause major health complications, especially in the tiny blood vessels in the kidneys, nerves, and eyes. Type 2 also raises the risk of heart disease and stroke. People who are obese—more than 20% over their target body weight for their height—have an especially high risk of type 2 diabetes and the health problems that can follow. Treatment for type 2 diabetes involves keeping a healthy weight, eating right, and exercising. Some people need medication, as well.

Define Circadian rhythms, and describe how they are regulated by light exposure.

WRITE IN YOUR OWN WORDS COPIED FROM LESSON- Circadian rhythms are physical, mental, and behavioral changes that follow a 24-hour cycle and can influence our bodies' important functions, such as hormone release, eating habits, body temperature, and digestion. Most people notice the effect of circadian rhythms on their sleep patterns. These rhythms respond primarily to the amount of light you are exposed to, which is why your circadian rhythm typically coincides with the sun's cycle. Darkness stimulates the pineal gland to start producing melatonin, while light causes that production to stop.

The thyroid and parathyroid glands work together to maintain blood calcium homeostasis. Discuss the actions of these glands in the cases of: Hypercalcemia Hypocalcemia Include the gland, hormone, cell type stimulated, and resulting process in your explanation.

WRITE IN YOUR OWN WORDS FROM LESSON- When levels of calcium in the blood increase (hypercalcemia), calcitonin is secreted in higher quantities. When calcium levels in the blood decrease (hypocalcemia), this causes the amount of calcitonin secreted to decrease.

Contrast the solubility type of steroid hormones vs. nonsteroidal hormones. Then, discuss how this property affects their transport in the blood and their ability to diffuse through the cell membrane.

WRITE IN YOUR OWN WORDS- Steroid hormones are lipid soluble which means they "cannot float freely among the bloodstream but must be bound to proteins in the plasma in order to travel." " Steroid hormones "diffuses through the cell membrane to enter the cytoplasm." Nonsteroidal hormones are water soluble substances which means "can be transported freely in the blood plasma, but they cannot diffuse through the cell membranes when they arrive at their destination. Instead, they must bind to extracellular receptors on the cell membrane."

Provide a brief description of each indicated step (A-F) shown in the hormonal negative feedback graphic.

WRITE IN YOUR OWN WORDS- Step A/Step 1: Receptors- senses that hormone levels have increased in the blood Step B/Step 2: Control Center- inhibits the endocrine gland- causing it to slow down or cease hormone secretion. Step C/Step 3: Effectors- hormone secretion is decreased, and blood levels return to normal Step D/Step 1: Receptors- senses hormones levels have decreased in the blood Step E/ Step 2: Control Center- the control center stimulates the endocrine gland causing it to increase in hormone secretion Step F/ Step 3: Effectors- hormone secretion is increased and blood levels return to normal

PTH and Calcitonin Interaction Bone remodeling is a process that goes on throughout life wherein new bone tissue is formed as mature bone. This is a lifelong process where mature bone tissue is removed from the skeleton and new bone tissue is formed. Bone remodeling is also impacted by the interaction of PTH and calcitonin with each other.

What Is Hyperthyroidism? Hyperthyroidism refers to any condition in which there is too much thyroid hormone produced in the body. The most common hyperthyroid pathology is Graves' disease. With Graves' disease, a person's antibodies attack the thyroid and cause it to secrete too much thyroid hormone. This type of autoimmune hyperthyroidism tends to run in families and occurs more often in young women. Typical hyperthyroidism symptoms include an elevated metabolic rate, rapid, irregular heart rate, nervousness, and sweating. Exophthalmos can result when the tissue behind the eyes becomes edematous and fibrous, causing the eyeballs to protrude. Hyperthyroidism can be permanently cured by surgical removal of all or most of the thyroid gland.

Parathyroid Hormone The parathyroid glands release parathyroid hormone (PTH). PTH is secreted directly into the bloodstream. It travels to target cells in the bones, kidneys, and gastrointestinal system resulting in the release of calcium from the bones and into the extracellular fluid. The parathyroid hormone acts to increase blood calcium levels through osteoclasts' stimulation, which break down the bone, causing calcium release into the blood. PTH and calcitonin (produced by the thyroid) work together to maintain calcium homeostasis.

What Is Hypothyroidism? Hypothyroidism is an abnormally low thyroid gland activity and means that the damaged thyroid gland cannot make enough thyroid hormones to keep the body running normally. The pituitary gland secretes increasing amounts of TSH in a futile attempt to make more TH. This results in an enlarged, protruding yet nonfunctional thyroid gland known as a goiter. Hypothyroidism can result from an autoimmune disease such as Hashimoto's thyroiditis, dietary iodine deficiency, surgical removal of the thyroid, or inadequate TRH or TSH release. It occurs more frequently in women than men. The most common cause of hypothyroidism is Hashimoto's thyroiditis. In this condition, the body produces antibodies that damage the thyroid gland, causing it to be unable to make enough thyroid hormone.

The physical, mental, and behavioral changes that follow a 24-hour cycle and can influence our bodies' important functions, such as hormone release, eating habits, body temperature, and digestion, are known as _________ rhythms.

circadian

The release of _____ is triggered by the condition of hyperglycemia.

insulin