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A+P II Ch. 18

The Endocrine System

What two systems act together to coordinate functions of all body systems? Differences? Nervous system (neurotransmitters, fast response, brief effect, specific target) and Endocrine system (hormones, slow response, long effect, broad influence).
What is a hormone? A mediator molecule released in one part of the body but regulates activity of cells in other parts.
Name 5 endocrine glands. Pituitary, thyroid, parathyroid, adrenal, and pineal glands.
Name 13 organs and tissues that sometimes act as endocrine glands. Hypothalamus, thalamus, pancreas, ovaries, testes, kidneys, stomach, liver, small intestine, skin, heart, adipose tissue, and placenta.
How do hormones get to target cells? Endocrine gland secretes hormones into interstitial fluid>enter blood and transported by CV system> only cells with receptors (target cells) respond> hormones change target cell activity.
What is a hormone receptor? Terms for change in number? Target cell proteins that bind hormone. Receptors constantly synthesized and broken down. Down-regulation (decreased number of receptors) and up-regulation (increase in number).
Types of hormones based on relative location of targets. Circulating hormones (circulate in blood throughout body) and Local hormones (Paracrine-act on neighboring cells. Autocrine- act on the same cell that secreted them)
Chemical classes of hormones and examples. Lipid-soluble= Steroids, made from cholesterol. (Ex:those from adrenal cortex. Estrogen, Progesterone, Testosterone) Water-soluble= Amine made from amino acids and Peptide/protein made of arachnoid (a fatty) acid (Ex:Prostoglandins (are Eicosanoids,local)
What is the difference in the way hormones are transported in the blood? Water-soluble hormones usually travel free in the blood (not attached to transport proteins). Lipid-soluble hormones are usually attached to transport proteins.
Describe the mechanism of action of lipid-soluble hormones. Hormone diffuses across plasma membrane>binds to receptor in cytoplasm>hormone-receptor complex binds to DNA>specific gene activated>protein (often an enzyme) produced> metabolic activity changed.
Mechanism of action of water-soluble hormones. Hormone (1st messenger) binds to plasma receptor>2nd messenger molecules produced in cell>2nd m. cause changes in activity of cell proteins (like enzymes or transport proteins)>2nd m. quickly inactivated.
What does the responsiveness of the target cell to the hormone depend on (3)? Hormone's concentration. Abundance of target cell receptors. Influence exerted by other hormones.
What are 3 effects different hormones can have on each other? Permissive (hormone action requires a 2nd hormone to be present), synergistic (2 working together produce a greater effect), or antagonistic effects (2 have opposite action, such as glucose and insulin).
Give 3 ways, with examples, that hormone secretion can be simulated. Signals from NS (Ex:nerve signals increase secretion of oxytocin, causing labor contractions). Chemical changes in blood (Ex:Elevated BG stimulate secretion of insulin). Other hormones (Ex:TSH released by pituitary causes secretion of T3 + T4 by thyroid).
How most hormone secretion is inhibited. Negative feedback.
Synthetic form of oxytocin. Pitocin.
Location of pituitary gland and its structure. Connected to what other structure and that structures significance. Located in the sella trucica of the sphenoid bone. 2 parts, anterior and posterior. Connected to hypothalamus by the infundibulum. Hypothalamus is a major link between nervous and endocrine system.
What gland does the hypothalamus regulate? Through what system? Type of inhibition? Hypothalamus connected to anterior pituitary by hypophyseal portal system. "Portal" because blood flows from capillaries to vein to capillaries. Hypothalamic releasing and inhibiting hormones and negative feedback regulate system.
Name 4 anterior pituitary hormones that stimulate other endocrine glands. Give term. Tropic Hormones:1)TSH (thyroid-stiumulating) or thyrotropin 2)ACTH(Adrenocorticotropic) or corticotropin 3)FSH(follicle-stimulating) 4)LH (luteinizing)
Name 3 hormones of the anterior pituitary that stimulate non-endocrine cells. Give term. Non-tropic hormones 1)hGH (human growth) or somatostatin 2)PRL (prolactin) 3)MSH (melanocyte-stimulating
Glands, target cells, effect, and control of TSH. Hypothalamic releasing hormone of hypothalamus stimulates secretion of thyroid-stimulating hormone by pituitary > thyroid secretes thyroid hormones > elevated thyroid hormones inhibit secretion of hypothalamic releasing hormone and TSH.
Glands, target cells, effect, and control of ACTH. Hypothalamic releasing hormone released by hypothalamus > anterior pituitary releases ACTH > adrenal cortex releases cortisol > Elevated cortisol inhibits release of hypothalamic releasing hormone and ACTH.
Glands, target cells, effect, and control of FSH. Hypothalamic releasing hormone > anterior pituitary releases follicle-stimulating hormone > Ovaries develop follicles(oocytes) or testes produce sperm > elevated estrogen or testosterone inhibit release of hypothalamic releasing hormone.
Glands, target cells, effect, and control of LH. Hypothalamic releasing hormone > anterior pituitary releases luteinizing hormone > Ovaries secrete estrogen and progesterone or testes produce testosterone > Elevated sex hormones provides negative feedback to hypothalamus.
Glands, target cells, effect, and control of hGH. Low BG > hypothalamic releasing hormone > anterior pituitary releases hGH > liver, skeletal muscle, cartilage, bone, and other tissues synthesize insulin-like growth factors (IGFs). IGFs up BG, cell growth and division, + tissue repair > BG
Target cells and effect of PRL. Anterior pituitary releases Prolactin, targeting mammary glands to secrete milk if primed by other hormones.
Effect of MSH. Increased levels of melanocyte-stimulating hormone results in darkening of the skin, separate from genetic skin color.
What is the role of the posterior pituitary? Does not synthesize hormones, but stores and releases those made by the hypothalamic neurosecretory cells in the hypothalamus. The hormones are transported down the axons that form the hypothalamohypophyseal tract into the pituitary.
Name two hormones stored in the posterior pituitary. Oxytocin (OT) and Antidiuretic hormone (ADH).
What controls OT secretion? Nerve impulses initiated by uterine distention (increased by uterine contraction) or nursing create positive feedback to increase oxytocin levels. OT is inhibited with the event of childbirth or cessation of nursing NOT negative feedback.
What cells do OT target? Effect? Oxytocin stimulates contraction of the uterus and milk ejection of the mammary glands.
What are the target cells and effects of ADH? Antidiuretic hormone or Vasopressin encourages the kidneys to retain more water and decrease urine output, the suderiferous glands to lose less water, and vasoconstriction to increase blood pressure.
What controls ADH secretion? The hypothalamus is stimulated to secrete ADH when there is high blood osmotic pressure caused by dehydration or decreased blood volume (due to hemorrhage, diarrhea, or excessive sweating). Low blood osmotic pressure provides negative inhibition.
Where is the thyroid gland located? How many lobes? Inferior to the larynx. 2 lobes connected by isthmus.
Describe the microscopic anatomy of the thyroid gland. Follicular cells in walls of follicles synthesize thyroid hormones. Parafollicular cells (C cells) locted between follicles and produce hormone calcitonin.
Name the thyroid hormones (TH). Thyroxine or tetraiodothyronine (T4) and triiodothyronine (T3)
Target cells, effect, and control of TH. Most body cells have thyroid hormone receptors. TH increases metabolic rate, stimulates body growth and development of the nervous system. TSH > TH. High TH> less TSH.
Effect of TH involving body temperature. Term? Calorigenic effect. TH increases the use of ATP. When ATP is broken down for energy, heat is released, helping maintain body temperature.
Target cells, effect, and control of hormone released by C cells. Parafollicular (C) cells of thyroid release calcitonin > inhibit activity of osteoclasts >less bone break down and release of Ca+ into the blood. High blood Ca+ stimulates calcitonin secretion. Low Ca+ levels inhibit secretion (neg. feedback)
Posterior endocrine glands in throat. Number? Hormone? The 4 (usually) parathyroid glands are located on the posterior surface of the lateral lobes of the thyroid gland. They secrete parathyroid hormone (PTH).
What mineral levels do PTH regulate? Calcium, magnesium, and phosphate.
What are the target cells and effects of PTH? Kidneys: Increase synthesis of Vit. D > increases absorption of Ca+ from food. Osteoclasts of bone: Stimulate osteoclasts >break down bone matrix releasing stored Ca+ into the blood.
What controls PTH secretion. Low blood calcium levels stimulate secretion. High levels inhibit (negative feedback).
What is the difference between the effects of the hormones of the thyroid and parathyroid on osteoclasts? Thyroid's calcitonin inhibits the activity of osteoclasts (less release of Ca+ into blood) and parathyroid's PTH stimulates the activity of osteoclasts (more Ca+ into blood).
Where are the adrenal glands located? One superior to each kidney.
What 3 hormones does the adrenal cortex secrete? Examples of each. 1)Mineralocorticoids (affect mineral homeostasis) (ex:Aldosterone)2)Glucocorticoids (affect glucose homeostasis) (ex:cortisol) 3)Androgens (have masculinizing effects) (ex: Dehydroepiandrosterone/DHEA, only important in females)
What is the inner part of the adrenal gland and what does it do? The adrenal medulla is a modified sympathetic ganglion of ANS. It intensifies sympathetic responses by secreting epinephrine and norepinephrine.
Describe the effect of the hormone secreted by the adrenal cortex that targets the kidneys. Effect and control. Aldosterone (a mineralocorticoid) ups reabsorption of Na + H2O from urine + ups secretion of K and H into urine. Stimulated by Angiotensin II (decr. BP from low blood volume) and high levels of extracellular K. Neg. feedback when low K.
What type of hormone is cortisol? A Glucocorticoids (affect glucose homeostasis) from the adrenal cortex.
What effect does cortisol have on muscle and adipose tissue? Helps body respond to stress: up breakdown of protein in muscle to provide amino acids to make new proteins, increasing formation of glucose and increasing lipolysis in adipose tissue to provide energy sources for metabolism.
What are the target cells of cortisol? Targets muscle, liver, adipose tissue, and white blood cells.
How does cortisol affect WBCs? Cortisol inhibits immune and inflammatory responses. This explains why you get sick when you have been stressed for a long time.
What stimulates and what inhibits cortisol secretion? ACTH (from hypothalamic releasing hormone stimulated anterior pituitary) stimulates secretion by the adrenal cortex. Elevated cortisol levels inhibit secretion of ACTH (negative feedback).
What effect does DHEA have on males and females? What is its relationship to other tissues? DHEA can be converted to estrogens by other tissues. Assists in early growth of axillary and pubic hair in both sexes. Contributes to libido. Source of estrogen after menopause.
How do the hormones secreted by the adrenal medulla effect the body? Controlled by what? Controlled by sympathetic nervous system. Augments fight or flight response with release of epinephrine and norepi. to most cells of body. Increased HR, vasoconstriction to up BP, and increase diameter of bronchioles to increase air flow.
What endocrine system related organ is located in the first part of the small intestine? Main role of cells. Major hormones. Pancreas. 99% of cells are exocrine glands, producing digestive enzymes. The remainder are called pancreatic islets and secrete hormones glucagon and insulin.
What are the target cells, effects, and controller of insulin? High BG stimulates the secretion of insulin which targets most cells of the body. It increases facilitated diffusion of glucose into cells, formation of glycogen, and lipogenesis (formation of fatty acids). When BG is low, insulin secretion is inhibited.
What are the target cells, effects, and controller of glucagon? When BG is low, glucagon targets hepatocytes (liver cells) to increase glycogenolysis (breakdown glycogen to glucose) and gluconeogenesis (form glucose from lactic acid and amino acids). High BG inhibits.
What role do the ovaries play in the endocrine system? Secrete estrogen and progesterone that regulate menstrual cycle, maintain pregnancy and prepare mammary glands for lactation, and influence female secondary sex characteristics.
What role do the testes play in the endocrine system? Located within the scrotum, testes secrete testosterone that regulates sperm production and male secondary sex characteristics.
What is the pineal gland and where is it? Roof of third ventricle of brain. Secretes melatonin which helps set body's biological clock.
What endocrine structure atrophies in adults? Where is it and what does it do? The thymus is located behind the sternum between the lungs and secretes thymosin and thymopoietin. These hormones promote the maturation of T cells (immune system cells).
Two types of stress. Eustress is helpful stress. Distress is harmful.
What does the body do with stress? The body's homeostatic mechanisms attempt to counteract stress.
What can result from stressful conditions? Stages of this syndrome. Stress response or general adaptation syndrome (GAS). 3 stages: 1)initial flight-or-fight- fast acting and brief. 2)Resistance reaction- slower, longer, increased ACTH (thus cortisol), hGH, and TSH. 3)Exhaustion- w/prolonged stress.
What can result from prolonged exposure to cortisol? Wasting of muscles, suppression of immune system, ulceration of GI tract, and failure of pancreatic beta cells.
What cells of the pancreas secrete insulin? Beta cells.
Created by: 741879016