Ch. 16 The Endocrine System

Which organ is considered a "neuroendocrine" organ?

Hypothalamus

How does cortisol function during prolonged stress?

"stress hormone," cortisol causes an increase in your heart rate and blood pressure. It's your natural "flight or fight" response that has kept humans alive for thousands of years.

After hormones have exerted their effects, most hormones are removed from the blood and broken down by the ____________________ and ____________________. The resulting breakdown products are excreted in the ___________________ and _________________.

***Kidneys or liver** The resulting products= urine* or feces

List two things that stimulate the release of thyrotropin releasing hormone (TRH) from the hypothalamus

- exposure to infants to cold ... stimulates the hypothalamus to secrete thyrotropin-releasing hormone (TRH), which stimulates the anterior pituitary to release TSH, which then stimulates TH, body metabolism increases & heat is produced -Thyrotropin-releasing hormone (TRH) from the hypothalamus increases the release of thyroid-stimulating hormone (TSH) from the anterior pituitary gland. TSH stimulates the thyroid gland to release the prohormone thyroxine (T4) alongside the active metabolite triiodothyronine (T3)

What are the most frequent symptoms of an anterior pituitary tumor?

-inappropriate lactation -lack of menses -infertility in females -impotence of males

List several metabolic functions of thyroid hormone.

-increases metabolic rates & heat production - promotes glucose/fat metabolism, protein synthesis, synthesis of cholesterol - regulates tissue growth & development: skeletal, muscular, nervous, reproductive system -promotes normal function of most body systems - maintains cardiac function & blood pressure - promotes normal GI tract - maintains integrity of skin, hair, nails

List three conditions that stimulate aldosterone secretion.

1. Decreasing blood volume 2. Decreasing blood pressure 3. Increasing blood levels of K+

Describe the three types of stimuli that trigger endocrine glands to release their hormones. Give an example of each type of stimulus.

1. Humoral Stimuli: Hormone release caused by altered levels of certain critical ions or nutrients. -ex: a low conc. of calcium in the blood, results in the parathyroid glands to secrete a parathyroid hormone(PTH), which increases blood calcium. -ex: insulin is released to increase blood glucose. -ex: aldosterone is released in response to low Na+ or high K+ blood levels. 2. Neural Stimuli: Nerve fibers stimulate hormone release. -ex: Stress. The sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines (norepinephrine & epinephrine) 3. Hormonal Stimuli: Hormones from one gland stimulate the release of hormones from other endocrine organs. -ex: Hypothalamus hormones stimulate the release of most anterior pituitary hormones. Anterior pituitary hormones stimulate other target endocrine glands to release their hormone

What are the four primary effects of insulin after it enters a cell? Which of these effects is the most important?

1. Insulin receptor is tyrosine kinase enzyme. This enzyme phosphorylates proteins which results in a cascade; causing glucose uptake by cells*** 2. After glucose enter cell, insulin triggers enzymes that CATALYZE OXIDATION OF GLUCOSE FOR ATP PRODUCTION***** (cellular respiration) first priority is energy production. **join glucose molecules to form glycogen *convert excess glucose to fat; particularly in adipose tissue -stimulate amino acids uptake/protein synthesis in muscle 3. ***Lowers blood glucose levels in three ways: - Enhances membrane transport of glucose into cells, especially fat and muscle cells - inhibits glycogenolysis: inhibits breakdown of glycogen to glucose - Inhibits gluconeogenesis: inhibits conversion of amino acids or fats to glucose 4. Removes glucose from blood - to be used for energy (ATP) first*** - to be converted and stored in other forms: Glycogen** & Fats* - promotes protein synthesis in muscle by stimulating amino acid uptake

List the three cardinal signs of diabetes mellitus.

1. Polyuria: excessive urine output -excess glucose in the blood acts as an osmotic diuretic; inhibits water reabsorption by kidneys - causes dehydration and decreased blood volume 2. Polydipsia: excessive thirst -from water loss due to polyuria -from dehydration brought on by vomiting 3. Polyphagia: excessive hunger and food consumption -Glucose is available but cells cannot take up glucose -cells are "starving" -the body uses fat and protein stores for energy metabolism

Describe the two mechanisms of hormone action at target cells. Which class of hormones acts by each mechanism and why does it act by this mechanism?

1. Water-soluble hormones (all amino acid-based hormones except thyroid hormone) -act on plasma membrane receptors -cannot enter cell (so receptors must be in membrane) -Act via G proteins and second messengers 2. Lipid-soluble hormones (steroid & thyroid hormones) -act on intracellular receptors -can enter cell (so receptors are inside the target cell) -directly activate gene

Name the three layers of the adrenal cortex, the hormones produced in each layer, and the major functions of each hormone

1. Zona glomerulosa (superficial layer) - Mineralocorticoids (aldosterone) : controls mineral & water balance of blood 2. Zona Fasciculata (middle layer) - Glucocorticoids (cortisol) : involved in energy metabolism & stress resistance 3. Zona reticularis ( innermost layer ) - Gonadocortiocoids : Adrenal sex hormones (testosterone, estrogen) GO FIND REX. MAKE GOOD SEX.

Hormones that bind to plasma membrane receptors are able to cause their effects at even very low concentrations. How is this possible?

A single amino acid hormone molecule binding to a plasma membrane receptor can generate millions of product molecules. - It triggers a cascade of chemical reactions in cell (amplification effect)

Why is the pancreas classified as both an exocrine and endocrine organ?

Acinar cells (exocrine function): - make up most of the pancreas - produce enzyme-rich juice for digestion; carried by ducts to duodenum of small intestine Pancreatic islets or (Islets of Langerhans): endocrine - Alpha cells: produce glucagon; increases blood glucose - Beta cells: produce insulin; decreases blood glucose

Name the two hormones produced by the pancreas, the specific cells that produce these hormones, and the function of each hormone.

Alpha cells: produce glucagon; increases blood glucose and increase blood pressure - Beta cells: produce insulin; decreases blood glucose and decrease blood pressure

Name the two chemical classes of hormones and the hormones included in each class.

Amino acid bases hormones -Most hormones, amino acid derivatives, peptides, proteins Steroids - Gonadal (sex) hormones: Estrogen, Testosterone, Progesterone -Adrenocortical hormones

How does the hypothalamus communicate with the anterior pituitary? How does the hypothalamus communicate with the posterior pituitary? What are these communication systems called?

Anterior pituitary: Hypothalamic hormones released into special blood vessels (the hypophyseal portal system) control the release of anterior pituitary hormones. Posterior pituitary: Action potentials travel down the axons of hypothalamic neurons, causing hormone release from their axon terminals in the posterior pituitary. Anterior: Hypophyseal portal system Posterior: Hypothalamic-hypophyseal tract

Name the hormones released by the anterior pituitary and posterior pituitary. List the basic functions of these hormones. Which of these hormones are tropic hormones?

Anterior: LH (Lutenizing hormone): Stimulates testes to release testosterone & ovaries TSH(thyroid stimulating hormone): stimulates the thyroid gland to release thyroid hormone FSH (Follicle-stimulating hormone): maturation of the egg, and produces the sperm GH (Growth hormone): Stimulates growth of tissues ACTH (adrenocorticotrophic hormone): stimulates the adrenal cortex to release glucocorticoids. PRL (Prolactin): stimulates milk Posterior: Oxytocin: stimulates contractions during labor, triggers milk ejection(causes release of milk), acts a neurotransmitter in brain (cuddle hormone) ADH (Anti-Diuretic Hormone): inhibits or prevents urine formation to regulate water balance & avoid dehydration TROPIC: ACTH, LH, FSH, TSH

What are the adverse effects of excessive levels of cortisol?

Anti-inflammatory & anti-immune effects - depress cartilage & bone formation - inhibit inflammation & tissue/wound repair - disrupt normal cardiovascular, nervous, & gastrointestinal function - depress immune function which leads to increased infections

Why do blood glucose levels remain high in diabetes mellitus?

Because glucose is unable to enter cells and cannot be used for ATP!!!

Why does drinking alcoholic beverages cause a person to urinate more?

Because it inhibits ADH secretion and causes you to urinate more. The dry mouth & intense thirst of a "hangover" reflect this dehydrating effect.

Why is the posterior pituitary not considered a true endocrine gland

Because, this lobe is a hormone-storage area and not a true endocrine gland that manufactures hormones.

The major targets of growth hormone are ________________ and ___________________.

Bone & Skeletal muscle

What is a hormone?

Chemical messengers secreted by cells into extracellular fluids and transported in blood to specific distant target cells. -Response is SLOW -Duration is LONGER ACTING - Targets are DISTANT

What are the primary functions of cortisol?

Cortisol's function during stress: - glucose, fatty acids, amino acids... Causes gluconeognesis (prime metabolic effect) which is the formation of glucose from fats & proteins (non-carbs). Mobilizes fatty acids from adipose tissue... increases fatty acids use for energy (ATP), saves glucose for brain. Breaks down stores proteins, for repair or enzyme synthesis

What is the difference between diabetes mellitus and diabetes insipidus? What symptoms do they have in common? What would be found in the urine of a patient with diabetes mellitus but not in the urine of a patient with diabetes insipidus?

Diabetes insipidus should not be confused with diabetes mellitus (DM), which results from insulin deficiency or resistance leading to high blood glucose, also called blood sugar. Diabetes insipidus and diabetes mellitus are unrelated, although they can have similar signs and symptoms, like excessive thirst and excessive urination. Diabetes mellitus is far more common than diabetes insipidus and receives more news coverage. Diabetes mellitus has two main forms, type 1 diabetes and type 2 diabetes. Diabetes insipidus is a different form of illness altogether Diabetes insipidus (DI) is a rare disease that causes frequent urination. The large volume of urine is diluted, mostly water. To make up for lost water, a person with diabetes insipidus may feel the need to drink large amounts and is likely to urinate frequently, even at night, which can disrupt sleep and, on occasion, cause bedwetting. Because of the excretion of abnormally large volumes of dilute urine, people with diabetes insipidus may quickly become dehydrated if they do not drink enough water. In urine: -Diabetes mellitus: Glycosuria: excess glucose eliminates in urine & lipidemia (fats in blood) - Diabetes insipidus: ADH is stored in the pituitary gland, which is located behind the bridge of the nose. Patients with diabetes insipidus have high amounts of urine that is diluted (clear) because of this inability to control the amount of water in the urine.

How does growth hormone regulate metabolism and growth?

Direct actions on metabolism: -Mobolizes fats from fat deposits; Encourages use of fatty acids for fuel (ATP) - Decreases rate of glucose uptake/metabolism by cells; keeps blood glucose levels high (anti-insulin effect) -Promotes glycogen breakdown in liver & glucose release to blood; increases blood glucose (anti-insulin effect) - Encourages protein synthesis by increasing amino acid uptake by cells Indirect actions on growth: - Stimulates most body cells to enlarge & divide -Mediates growth via growth-promoting proteins (IGFs): Insulin-like growth facts; liver, skeletal muscle, bone produce IGFs in response to GH IGFs stimulate: -uptake of amino acids from blood and into cells for cell division - Formation of collagen, bone, & skeletal muscle

By what mechanism does thyroid hormone affect its target cells? What other hormones act by this same mechanism?

Direct gene activation 1. TH enters target cell 2. Binds to & activates intracellular receptor 3. Activated receptor-hormone complex binds to specific DNA region (activates gene) 4. Initiates transcription of DNA to mRNA 5. mRNA is translated on cytoplasmic ribosomes 5. Specific proteins are produced Steroid hormones

Name two hormones involved in the stress response. Which glands produce these hormones?

Epinephrine Norepinephrine The adrenal medulla

Name two hormones that increase blood glucose levels. Which glands produce these hormones?

Epinephrine, Glucagon Adrenal medulla, Pancreas

Which gland and hormone is the major regulator of blood calcium homeostasis? What stimulates the release of this hormone? What organs are the major targets of this gland and what effects are produced in these target organs? What is the ultimate effect on blood calcium levels when this hormone is released?

Gland: Parathyroid Gland Hormone: Parathyroid hormone Simulates: controls calcium homeostasis Organs: - Skeleton: stimulates osteoclasts to reabsorb/ dissolve bone matrix - Kidneys: stimulates reabsorption of calcium by kidneys ( and secretion of phosphate), promotes activation of Vitamin D by Kidneys - Intestines: Increases absorption of calcium by intestines by promoting activation of Vitamin D by kidneys (vitamin D requires for absorption of calcium from food) Decreasing blood calcium stimulates PTH release. Increasing blood calcium inhibits PTH release.

What is goiter? What causes goiter?

Goiter: enlarged thyroid gland Cause: due to lack of Iodine. Follicular cells produce colloid but cannot iodinate it --> nonfunctional thyroglobulin -low TH levels cause anterior pituitary to secrete more TSH in attempt to stimulate thyroid gland -This causes thyroid gland to make more unusable thyroglobulin colloid -thyroid gland enlarges due to colloid storage

Which chemical class of hormones do the gonadal hormones belong to? What other endocrine gland secretes hormones belonging to this same chemical class?

Gonads produce steroid sex hormones Ovaries, Testes, Placenta, Adipose tissue, Heart, Kidneys, gastrointestinal tract, skeleton, skin, thymus

Is the stimulus for insulin and glucagon release hormonal, humoral, or neural? What is the specific stimulus for each hormone?

Humoral Stimuli: Hormone release caused by altered levels of certain critical ions or nutrients. -ex: insulin is released to decrease blood glucose. - ex: glucagon is released to increases blood glucose

Name two causes of hypoglycemia. Which one is the most common cause?

Insulin is a hypoglycemic hormone!!! Secreted by beta cells of the pancreas in response to rise in blood sugar after a meal. more common -Hypoglycemia may also happen if you don't eat as much food as usual after taking diabetes medication, or if you exercise more than you normally would.

The brain, liver, kidneys, and red blood cells can use glucose without the help of insulin. Why is insulin necessary for other cells to be able to use glucose?

Insulin removes glucose from blood - to be used for energy (ATP) first*** -To be converted and stored in other forms -Glycogen** - Fats* - promotes protein synthesis in muscle by stimulating amino acid uptake Its important for other cells to use glucose when the body needs more energy after not eating.

What causes lipidemia and ketoacidosis in diabetes mellitus?

Lipidemia: bc goucse unable to enter cells, cannot be used for ATP - fats are mobilized to be used for cellular fuel--> lipidemia (fats in blood) -If severe--> ketones from fatty acid metabolism accumulate --> ketonuria and ketoacidosis Ketoacidosis is life-threatening--> blood pH drops (more acidic) - the nervous system initiates rapid deep breathing to blow off carbon dioxide and increase blood pH - untreated ketoacidosis disrupts heart activity and O2 transport whichList the three cardinal signs of diabetes mellitus depresses the nervous system and leads to coma or death

Describe the location and structure of the adrenal glands.

Location: on top of kidneys Structure: 1. Adrenal medulla (inner part): contains nervous tissue, part of the sympathetic nervous system 2. Adrenal cortex (outer part): 3 layers of glandular tissue, synthesizes & secretes corticosteroids (steroid hormones made from cholesterol)

What hormones are produced by the ovaries and testes? What are the functions of these hormones?

Ovary: Progesterone & Estrogen -Maturation of female reproductive organs (estrogen) • Appearance of secondary sexual characteristics (estrogen) • Breast development (estrogen + progesterone) • Cyclic changes in uterine mucosa (estrogen + progesterone) - Menstrual cycle Testes: Testosterone Maturation of male reproductive organs • Development of male secondary sexual characteristics • Responsible for sex drive • Necessary for normal sperm production • Maintains reproductive organs in functional state

Which organs or glands have both exocrine and endocrine functions?

Pancreas, gonads (testes, ovaries), placenta -Exocrine glands: Ducts, sweat & saliva -Endocrine glands: lack ducts, release hormones into extracellular tissue fluid

How do insulin and glucagon regulate blood glucose levels?

Pancreatic Islets have clusters of endocrine cells. -Alpha cells produce glucagon; increases blood glucose - Beta cells produce insulin; decreases blood glucose

Define permissiveness, synergism, and antagonism. Give an example of each.

Permissiveness: One hormone needs another hormone to produce its full effects. -ex: Reproductive hormones regulate reproductive system development. Thyroid hormone is necessary for normal development of reproductive structures. Synergism: more than one hormone produces the same effects on target cell... combined effects are amplified. -ex: Glucagon from pancreas and epinephrine from adrenal glands cause the liver to release glucose to bloodstream. Amount of glucose released by both hormones acting together is 150% Antagonism: one hormone opposes the action of another hormone. -ex: insulin lowers blood glucose levels & Glucagon raises blood glucose levels.

A tumor of the adrenal medulla that produces episodes of uncontrolled sympathetic nervous system activity is called a _____________________________.

Pheochromocytoma

List the hormones and hormone functions of the following organs: placenta, adipose tissue, gastrointestinal tract, heart, kidneys, skin, thymus

Placenta - Temporary endocrine organ - Fetal nutrition and waste removal - Influences course of pregnancy - Secretes estrogens, progesterone, human chorionic gonadotropin (hCG) • Pregnancy tests detect hCG Adipose tissue - Leptin - appetite control • Produces sensation of satiety (fullness) - Suppresses appetite • Stimulates increased energy expenditure • More fat = more leptin in blood • Plays role in appetite suppression and regulation of body size Enteroendocrine cells of gastrointestinal tract - Gastrin stimulates release of HCl from stomach - Ghrelin from stomach stimulates food intake - Secretin stimulates liver and pancreas to release bicarbonate - Cholecystokinin stimulates pancreas to release enzymes and gallbladder to release bile (don't need to know for test) Heart - Atrial natriuretic peptide (ANP) • Decreases blood Na+ concentration • Therefore decreases blood volume/pressure Kidneys - Erythropoietin stimulates bone marrow produces more red blood cells - Renin initiates the renin-angiotensin-aldosterone mechanism increases blood pressure Skin - Cholecalciferol - precursor of Vitamin D - Produced by exposure to ultraviolet radiation (sunlight) • UV light --> cholecalciferol in skin --> blood -->modified in liver --> activated in kidneys (calcitriol) • Active Vitamin D (calcitriol) needed for intestinal absorption of calcium Thymus - Large in infants and children - Shrinks as age • Then composed of adipose /fibrous connective tissues - Involved in normal development of T lymphocytes and immune response - Thymulin, thymopoietins, thymosins - Classified as hormones, but act as paracrines • Act locally on neighboring cells

How do the anterior and posterior pituitary glands differ anatomically and physiologically? What is meant by adenohypophysis and neurohypophysis?

Posterior pituitary: Neural tissue, releases neurohormones which are produced by the hypothalamus. Hypothalamic-hypophyseal tract. The posterior pituitary just stores hormones and does not manufacture them. Posterior pituitary + infundibulum = neurophyophysis Anterior Pituitary: Adenohypophysis (composed of glandular tissue) Manufactures & releases many hormones. Out-pocketing of oral mucosa (epithelial tissue). - Vascular connection to hypothalamus = Hypophyseal portal system (2 capillary beds, plexuses connected by veins. Carries releasing & inhibiting hormones from hypothalamus to anterior pituitary to regulate hormone secretion from anterior pituitary.

The release of aldosterone in response to low blood volume and blood pressure is regulated by the _________________________________________________________ mechanism. Explain the steps of this mechanism beginning with decreased blood volume and pressure and ending with increased blood volume and pressure.

Renin-angoitension-aldosterone mechanism 1. Decreased blood volume & pressure 2. Kidneys release renin 3. forms angoitension II 4. adrenal cortex releases aldosterone 5. Kidneys reabsorb Na/ H2O 6. blood pressure increases

Name the six tropic hormones released by the hypothalamus. Which gland do these hormones stimulate or inhibit?

TSH: stimulates the thyroid gland to make & release thyroid hormone. ACTH: stimulates the adrenal cortex to release glucocorticoids FSH: stimulates the maturation of eggs and production of sperm. LH: stimulates the release of steroid hormones in gonads-- the ovaries & the testes

Which specific gland intensifies the activities of the sympathetic nervous system during acute, short-term stress? Which hormones are produced by this gland? How do these hormones prolong the fight-or-flight response?

The Adrenal Medulla intensifies the activities of the sympathetic nervous system. Catecholamines: Epinephrine & Norepinephrine Prolong: -Vasoconstriction -Increased heart rate -increased bronchial dilation - increased blood glucose levels - blood diverted to brain, heart, & skeletal muscle

Which organ system can override the endocrine system and make adjustments to maintain homeostasis? Describe a situation in which the endocrine system might be overridden.

The Nervous System can override normal endocrine controls and thus maintain homeostasis. - Under severe stress, hypothalamus and sympathetic nervous system are activated.... Override insulin control of blood glucose levels, blood glucose levels rise which is needed for flight or fight.

Which organ system works with the endocrine system to control or regulate body functions? Compare and contrast these two organ systems.

The Nervous System. Nervous system= response is quick, duration is short acting, targets are local(muscle cells, gland, other neurons) Endocrine is basically the opposite.

Describe the structural and functional relationships between the hypothalamus and the pituitary gland.

The posterior lobe is actually part of the brain. It derives from the hypothalamic tissue that grows downward, maintaining its neural connection with the bundle of axons called the hypothalamic-hypophyseal tract (which runs through the infundibulum). There is no direct neural connection between the anterior lobe and hypothalamus, but there's vascular. The primary & secondary capillary plexus make a portal system that releases & inhibits hormones secreted by neurons in the hypothalamus.

Describe the structure of thyroid hormone. What element is necessary for the production of thyroid hormone?

The thyroid hormone actually have 2 related compounds: (amino acid hormones containing iodine) - T4 (thyroxine): Major hormones secreted by thyroid follicles, 2 tyrosine amino acids + 4 iodine atoms -T3 (triiodothyronine): Formed at target tissues by converting T4 to T3, more active form, 2 tyrosine amino acids + iodine atoms Iodine is necessary!!!

How do autocrines and paracrines differ from hormones?

They are local chemical messengers - not long distance messengers - not considered part of the endocrine system SHORT - DISTANCE MESSENGERS!! Autocrines exert effects on the same cells that secrete them. Paracrine affect local cells but not those that secrete them.

The body's major metabolic hormone is ___________________________________.

Thyroid hormone

Explain the hypothalamic-pituitary-target organ feedback loop as it relates to the following: Thyroid hormone Cortisol FSH and LH

Thyroid hormone: Hypothalamus--> TRH (Thyrotropin-releasing hormone)--> Anterior pituitary--> TSH (Thyroid-stimulating hormone)--> Thyroid gland--> Thyroid hormones--> target cells Cortisol: Hypothalamus --> Anterior pituitary --> Adrenal cortex--> increase in cortisol release of glucocorticoids to help with stressors/ metabolism FSH & LH: Hypothalamus--> Anterior pituitary--> LH & FSH--> testis or ovaries--> which produces testosterone (testis) or Estrogen, Progesterone (ovaries)

Synthesis/release of most hormones is controlled by ____________ feedback mechanisms.

negative

What are gonadocorticoids and what are their effects?

produced by zona reticularis - most are weak androgens (male sex hormones), converted to testosterone ( some estrogen) in tissues May contribute to: - onset of puberty - axillary & pubic hair development - sex drive in women - estrogens in postmenopausal women

Hormones circulate through blood to all body cells, but only cells with __________________ for a specific hormone will respond to that hormone.

receptors

Which specific cells produce thyroid hormone? Which specific cells produce calcitonin?

thyroid hormones= follicular cells calcitonin= parafollicular cells

Synthetic glucocorticoids such as prednisone are often given for arthritis or after tissue transplant surgery. Why?

to decrease the inflammation and help with any allergies or to help the immune system from rejecting the new transplant

Define tropic hormone, and give an example.

tropic hormone= stimulating hormones; they have other endocrine glands as their target. - ex: TSH stimulates the thyroid gland to make and release thyroid hormone.