16 - Dr. Jerry Cronin

16 - Dr. Jerry Cronin

PowerPoint Lecture Slides prepared by Janice Meeking, Mount Royal College CHAPTER 16 The Endocrine System: Part B Copyright 2010 Pearson Education, Inc. The Posterior Pituitary Contains axons of hypothalamic neurons Stores antidiuretic hormone (ADH) and

oxytocin ADH and oxytocin are released in response to nerve impulses Both use PIP-calcium second-messenger mechanism at their targets Copyright 2010 Pearson Education, Inc. Oxytocin Stimulates uterine contractions during childbirth by mobilizing Ca2+ through a PIP2Ca2+ second-messenger system Also triggers milk ejection (letdown reflex) in women producing milk Plays a role in sexual arousal and orgasm in males and females Copyright 2010 Pearson Education, Inc.

Antidiuretic Hormone (ADH) Hypothalamic osmoreceptors respond to changes in the solute concentration of the blood If solute concentration is high Osmoreceptors depolarize and transmit impulses to hypothalamic neurons ADH is synthesized and released, inhibiting urine formation Copyright 2010 Pearson Education, Inc. Antidiuretic Hormone (ADH) If solute concentration is low ADH is not released, allowing water loss Alcohol inhibits ADH release and causes copious urine output

Copyright 2010 Pearson Education, Inc. Homeostatic Imbalances of ADH ADH deficiencydiabetes insipidus; huge output of urine and intense thirst ADH hypersecretion (after neurosurgery, trauma, or secreted by cancer cells) syndrome of inappropriate ADH secretion (SIADH) Copyright 2010 Pearson Education, Inc. Thyroid Gland Consists of two lateral lobes connected by a median mass called the isthmus Composed of follicles that produce the glycoprotein thyroglobulin

Colloid (thyroglobulin + iodine) fills the lumen of the follicles and is the precursor of thyroid hormone Parafollicular cells produce the hormone calcitonin Copyright 2010 Pearson Education, Inc. Copyright 2010 Pearson Education, Inc. Figure 16.8 Thyroid Hormone (TH) Actually two related compounds T4 (thyroxine); has 2 tyrosine molecules + 4 bound iodine atoms T3 (triiodothyronine); has 2 tyrosines + 3 bound iodine atoms

Copyright 2010 Pearson Education, Inc. Thyroid Hormone Major metabolic hormone Increases metabolic rate and heat production (calorigenic effect) Plays a role in Maintenance of blood pressure Regulation of tissue growth Development of skeletal and nervous systems Reproductive capabilities Copyright 2010 Pearson Education, Inc. Synthesis of Thyroid Hormone Thyroglobulin is synthesized and discharged into the follicle lumen Iodides (I) are actively taken into the cell, oxidized to iodine (I2), and released into the

lumen Iodine attaches to tyrosine, mediated by peroxidase enzymes Copyright 2010 Pearson Education, Inc. Synthesis of Thyroid Hormone Iodinated tyrosines link together to form T3 and T4 Colloid is endocytosed and combined with a lysosome T3 and T4 are cleaved and diffuse into the bloodstream Copyright 2010 Pearson Education, Inc. Thyroid follicle cells Colloid

1 Thyroglobulin is synthesized and discharged into the follicle lumen. Tyrosines (part of thyroglobulin molecule) Capillary 4 Iodine is attached to tyrosine in colloid, forming DIT and MIT. Golgi apparatus Rough ER Iodine 3 Iodide

is oxidized to iodine. 2 Iodide (I) is trapped (actively transported in). Iodide (I) Lysosome T4 T3 DIT (T2) MIT (T1) Thyroglobulin colloid

5 Iodinated tyrosines are linked together to form T3 and T4. T4 T3 T4 T3 6 Thyroglobulin colloid is endocytosed and combined with a lysosome. 7 Lysosomal enzymes cleave T4 and T3 from thyroglobulin colloid and hormones diffuse into bloodstream. Colloid in

lumen of follicle To peripheral tissues Copyright 2010 Pearson Education, Inc. Figure 16.9 Thyroid follicle cells Colloid 1 Thyroglobulin is synthesized and discharged into the follicle lumen. Capillary Tyrosines (part of thyroglobulin molecule)

Golgi apparatus Rough ER Colloid in lumen of follicle Copyright 2010 Pearson Education, Inc. Figure 16.9, step 1 Thyroid follicle cells Colloid 1 Thyroglobulin is synthesized and

discharged into the follicle lumen. Capillary Tyrosines (part of thyroglobulin molecule) Golgi apparatus Rough ER Iodide (I) 2 Iodide (I) is trapped (actively transported in). Colloid in lumen of

follicle Copyright 2010 Pearson Education, Inc. Figure 16.9, step 2 Thyroid follicle cells Colloid 1 Thyroglobulin is synthesized and discharged into the follicle lumen. Capillary Tyrosines (part of thyroglobulin molecule) Golgi apparatus

Rough ER Iodide (I) Iodine 3 Iodide is oxidized to iodine. 2 Iodide (I) is trapped (actively transported in). Colloid in lumen of follicle Copyright 2010 Pearson Education, Inc.

Figure 16.9, step 3 Thyroid follicle cells Colloid 1 Thyroglobulin is synthesized and discharged into the follicle lumen. Capillary Tyrosines (part of thyroglobulin molecule) 4 Iodine is attached to tyrosine in colloid, forming DIT and MIT. Golgi apparatus Rough

ER Iodide (I) Iodine 3 Iodide is oxidized to iodine. DIT (T2) MIT (T1) Thyroglobulin colloid 2 Iodide (I) is trapped (actively transported in). Colloid in

lumen of follicle Copyright 2010 Pearson Education, Inc. Figure 16.9, step 4 Thyroid follicle cells Colloid 1 Thyroglobulin is synthesized and discharged into the follicle lumen. Tyrosines (part of thyroglobulin molecule) Capillary

4 Iodine is attached to tyrosine in colloid, forming DIT and MIT. Golgi apparatus Rough ER Iodide (I) 2 Iodide (I) is trapped (actively transported in). Iodine 3 Iodide is oxidized to iodine. T4 T3

DIT (T2) MIT (T1) Thyroglobulin colloid 5 Iodinated tyrosines are linked together to form T3 and T4. Colloid in lumen of follicle Copyright 2010 Pearson Education, Inc. Figure 16.9, step 5

Thyroid follicle cells Colloid 1 Thyroglobulin is synthesized and discharged into the follicle lumen. Tyrosines (part of thyroglobulin molecule) Capillary 4 Iodine is attached to tyrosine in colloid, forming DIT and MIT. Golgi apparatus Rough ER

Iodide (I) Iodine 3 Iodide is oxidized to iodine. 2 Iodide (I) is trapped (actively transported in). Lysosome T4 T3 6 Thyroglobulin colloid is endocytosed and combined with a lysosome.

Copyright 2010 Pearson Education, Inc. DIT (T2) MIT (T1) Thyroglobulin colloid 5 Iodinated tyrosines are linked together to form T3 and T4. Colloid in lumen of follicle Figure 16.9, step 6 Thyroid follicle cells

Colloid 1 Thyroglobulin is synthesized and discharged into the follicle lumen. Tyrosines (part of thyroglobulin molecule) Capillary 4 Iodine is attached to tyrosine in colloid, forming DIT and MIT. Golgi apparatus Rough ER Iodine

3 Iodide is oxidized to iodine. 2 Iodide (I) is trapped (actively transported in). Iodide (I) Lysosome T4 T3 DIT (T2) MIT (T1) Thyroglobulin colloid

5 Iodinated tyrosines are linked together to form T3 and T4. T4 T3 T4 T3 6 Thyroglobulin colloid is endocytosed and combined with a lysosome. 7 Lysosomal enzymes cleave T4 and T3 from thyroglobulin colloid and hormones diffuse into bloodstream.

Colloid in lumen of follicle To peripheral tissues Copyright 2010 Pearson Education, Inc. Figure 16.9, step 7 Transport and Regulation of TH T4 and T3 are transported by thyroxine-binding globulins (TBGs) Both bind to target receptors, but T3 is ten times more active than T4 Peripheral tissues convert T4 to T3 Copyright 2010 Pearson Education, Inc.

Transport and Regulation of TH Negative feedback regulation of TH release Rising TH levels provide negative feedback inhibition on release of TSH Hypothalamic thyrotropin-releasing hormone (TRH) can overcome the negative feedback during pregnancy or exposure to cold Copyright 2010 Pearson Education, Inc. Hypothalamus TRH Anterior pituitary TSH Thyroid gland Thyroid hormones

Target cells Copyright 2010 Pearson Education, Inc. Stimulates Inhibits Figure 16.7 Homeostatic Imbalances of TH Hyposecretion in adultsmyxedema; endemic goiter if due to lack of iodine Hyposecretion in infantscretinism HypersecretionGraves disease Copyright 2010 Pearson Education, Inc. Copyright 2010 Pearson Education, Inc. Figure 16.10

Calcitonin Produced by parafollicular (C) cells Antagonist to parathyroid hormone (PTH) Inhibits osteoclast activity and release of Ca2+ from bone matrix Copyright 2010 Pearson Education, Inc. Calcitonin Stimulates Ca2+ uptake and incorporation into bone matrix Regulated by a humoral (Ca2+ concentration in the blood) negative feedback mechanism No important role in humans; removal of thyroid (and its C cells) does not affect Ca2+ homeostasis

Copyright 2010 Pearson Education, Inc. Parathyroid Glands Four to eight tiny glands embedded in the posterior aspect of the thyroid Contain oxyphil cells (function unknown) and chief cells that secrete parathyroid hormone (PTH) or parathormone PTHmost important hormone in Ca2+ homeostasis Copyright 2010 Pearson Education, Inc. Pharynx (posterior aspect) Thyroid gland

Parathyroid glands Chief cells (secrete parathyroid hormone) Oxyphil cells Esophagus Trachea (a) Copyright 2010 Pearson Education, Inc. Capillary

(b) Figure 16.11 Parathyroid Hormone Functions Stimulates osteoclasts to digest bone matrix Enhances reabsorption of Ca2+ and secretion of phosphate by the kidneys Promotes activation of vitamin D (by the kidneys); increases absorption of Ca2+ by intestinal mucosa Negative feedback control: rising Ca2+ in the blood inhibits PTH release Copyright 2010 Pearson Education, Inc. Hypocalcemia (low blood Ca2+) stimulates parathyroid glands to release PTH.

Rising Ca2+ in blood inhibits PTH release. Bone 1 PTH activates osteoclasts: Ca2+ and PO43S released into blood. Kidney 2 PTH increases 2+ Ca reabsorption in kidney tubules. 3 PTH promotes kidneys activation of vitamin D,

which increases Ca2+ absorption from food. Intestine Ca2+ ions PTH Molecules Copyright 2010 Pearson Education, Inc. Bloodstream Figure 16.12 Homeostatic Imbalances of PTH Hyperparathyroidism due to tumor Bones soften and deform Elevated Ca2+ depresses the nervous system and contributes to formation of kidney stones Hypoparathyroidism following gland trauma or

removal Results in tetany, respiratory paralysis, and death Copyright 2010 Pearson Education, Inc. Adrenal (Suprarenal) Glands Paired, pyramid-shaped organs atop the kidneys Structurally and functionally, they are two glands in one Adrenal medullanervous tissue; part of the sympathetic nervous system Adrenal cortexthree layers of glandular tissue that synthesize and secrete corticosteroids Copyright 2010 Pearson Education, Inc. Adrenal Cortex

Three layers and the corticosteroids produced Zona glomerulosamineralocorticoids Zona fasciculataglucocorticoids Zona reticularissex hormones, or gonadocorticoids Copyright 2010 Pearson Education, Inc. Capsule Zona glomerulosa Medulla Cortex Cortex Adrenal gland

Zona fasciculata Zona reticularis Medulla Kidney Adrenal medulla (a) Drawing of the histology of the adrenal cortex and a portion of the adrenal medulla Copyright 2010 Pearson Education, Inc.

Figure 16.13a Mineralocorticoids Regulate electrolytes (primarily Na+ and K+) in ECF Importance of Na+: affects ECF volume, blood volume, blood pressure, levels of other ions Importance of K+: sets RMP of cells Aldosterone is the most potent mineralocorticoid Stimulates Na+ reabsorption and water retention by the kidneys Copyright 2010 Pearson Education, Inc. Mechanisms of Aldosterone Secretion 1. Renin-angiotensin mechanism: decreased blood

pressure stimulates kidneys to release renin, triggers formation of angiotensin II, a potent stimulator of aldosterone release 2. Plasma concentration of K+: Increased K+ directly influences the zona glomerulosa cells to release aldosterone 3. ACTH: causes small increases of aldosterone during stress 4. Atrial natriuretic peptide (ANP): blocks renin and aldosterone secretion, to decrease blood pressure Copyright 2010 Pearson Education, Inc. Primary regulators Blood volume and/or blood pressure Other factors

K+ in blood Stress Blood pressure and/or blood volume Hypothalamus Kidney Heart CRH Renin Initiates

cascade that produces Direct stimulating effect Anterior pituitary Atrial natriuretic peptide (ANP) ACTH Angiotensin II

Inhibitory effect Zona glomerulosa of adrenal cortex Enhanced secretion of aldosterone Targets kidney tubules Absorption of Na+ and water; increased K+ excretion Blood volume and/or blood pressure Copyright 2010 Pearson Education, Inc.

Figure 16.14 Homeostatic Imbalances of Aldosterone Aldosteronismhypersecretion due to adrenal tumors Hypertension and edema due to excessive Na + Excretion of K+ leading to abnormal function of neurons and muscle Copyright 2010 Pearson Education, Inc. Glucocorticoids (Cortisol) Keep blood sugar levels relatively constant Maintain blood pressure by increasing the action of vasoconstrictors Copyright 2010 Pearson Education, Inc.

Glucocorticoids (Cortisol) Cortisol is the most significant glucocorticoid Released in response to ACTH, patterns of eating and activity, and stress Prime metabolic effect is gluconeogenesis formation of glucose from fats and proteins Promotes rises in blood glucose, fatty acids, and amino acids Copyright 2010 Pearson Education, Inc. Homeostatic Imbalances of Glucocorticoids HypersecretionCushings syndrome Depresses cartilage and bone formation Inhibits inflammation Depresses the immune system Promotes changes in cardiovascular, neural, and gastrointestinal function

HyposecretionAddisons disease Also involves deficits in mineralocorticoids Decrease in glucose and Na+ levels Weight loss, severe dehydration, and hypotension Copyright 2010 Pearson Education, Inc. Copyright 2010 Pearson Education, Inc. Figure 16.15 Gonadocorticoids (Sex Hormones) Most are androgens (male sex hormones) that are converted to testosterone in tissue cells or estrogens in females May contribute to The onset of puberty The appearance of secondary sex

characteristics Sex drive Copyright 2010 Pearson Education, Inc. Adrenal Medulla Chromaffin cells secrete epinephrine (80%) and norepinephrine (20%) These hormones cause Blood glucose levels to rise Blood vessels to constrict The heart to beat faster Blood to be diverted to the brain, heart, and skeletal muscle Copyright 2010 Pearson Education, Inc. Adrenal Medulla Epinephrine stimulates metabolic activities, bronchial dilation, and blood flow to skeletal

muscles and the heart Norepinephrine influences peripheral vasoconstriction and blood pressure Copyright 2010 Pearson Education, Inc. Short-term stress More prolonged stress Stress Nerve impulses Hypothalamus CRH (corticotropinreleasing hormone) Spinal cord

Corticotroph cells of anterior pituitary To target in blood Preganglionic sympathetic fibers Adrenal medulla (secretes amino acidbased hormones) Catecholamines (epinephrine and norepinephrine) Short-term stress response 1. Increased heart rate 2. Increased blood pressure 3. Liver converts glycogen to glucose and releases glucose to blood

4. Dilation of bronchioles 5. Changes in blood flow patterns leading to decreased digestive system activity and reduced urine output 6. Increased metabolic rate Copyright 2010 Pearson Education, Inc. Adrenal cortex (secretes steroid hormones) ACTH Mineralocorticoids Glucocorticoids Long-term stress response 1. Retention of sodium

and water by kidneys 2. Increased blood volume and blood pressure 1. Proteins and fats converted to glucose or broken down for energy 2. Increased blood glucose 3. Suppression of immune system Figure 16.16 Pineal Gland Small gland hanging from the roof of the third ventricle Pinealocytes secrete melatonin, derived from serotonin

Melatonin may affect Timing of sexual maturation and puberty Day/night cycles Physiological processes that show rhythmic variations (body temperature, sleep, appetite) Copyright 2010 Pearson Education, Inc. Pancreas Triangular gland behind the stomach Has both exocrine and endocrine cells Acinar cells (exocrine) produce an enzyme-rich juice for digestion Pancreatic islets (islets of Langerhans) contain endocrine cells Alpha () cells produce glucagon (a hyperglycemic hormone) Beta () cells produce insulin (a hypoglycemic

hormone) Copyright 2010 Pearson Education, Inc. Pancreatic islet (of Langerhans) (Glucagonproducing) cells (Insulinproducing) cells Pancreatic acinar cells (exocrine) Copyright 2010 Pearson Education, Inc. Figure 16.17

Glucagon Major target is the liver, where it promotes Glycogenolysisbreakdown of glycogen to glucose Gluconeogenesissynthesis of glucose from lactic acid and noncarbohydrates Release of glucose to the blood Copyright 2010 Pearson Education, Inc. Insulin Effects of insulin Lowers blood glucose levels Enhances membrane transport of glucose into fat and muscle cells Participates in neuronal development and learning and memory Inhibits glycogenolysis and gluconeogenesis

Copyright 2010 Pearson Education, Inc. Insulin Action on Cells Activates a tyrosine kinase enzyme receptor Cascade leads to increased glucose uptake and enzymatic activities that Catalyze the oxidation of glucose for ATP production Polymerize glucose to form glycogen Convert glucose to fat (particularly in adipose tissue) Copyright 2010 Pearson Education, Inc. Stimulates glucose uptake by cells Tissue cells

Insulin Pancreas Stimulates glycogen formation Glucose Glycogen Blood glucose falls to normal range. Liver Stimulus Blood glucose level

Stimulus Blood glucose level Blood glucose rises to normal range. Pancreas Liver Glucose Glycogen Stimulates glycogen Glucagon breakdown

Copyright 2010 Pearson Education, Inc. Figure 16.18 Homeostatic Imbalances of Insulin Diabetes mellitus (DM) Due to hyposecretion or hypoactivity of insulin Three cardinal signs of DM Polyuriahuge urine output Polydipsiaexcessive thirst Polyphagiaexcessive hunger and food consumption Hyperinsulinism: Excessive insulin secretion; results in hypoglycemia, disorientation, unconsciousness Copyright 2010 Pearson Education, Inc.

Copyright 2010 Pearson Education, Inc. Table 16.4 Ovaries and Placenta Gonads produce steroid sex hormones Ovaries produce estrogens and progesterone responsible for: Maturation of female reproductive organs Appearance of female secondary sexual characteristics Breast development and cyclic changes in the uterine mucosa The placenta secretes estrogens, progesterone, and human chorionic gonadotropin (hCG) Copyright 2010 Pearson Education, Inc.

Testes Testes produce testosterone that Initiates maturation of male reproductive organs Causes appearance of male secondary sexual characteristics and sex drive Is necessary for normal sperm production Maintains reproductive organs in their functional state Copyright 2010 Pearson Education, Inc. Other Hormone-Producing Structures Heart Atrial natriuretic peptide (ANP) reduces blood pressure, blood volume, and blood Na+ concentration

Gastrointestinal tract enteroendocrine cells Gastrin stimulates release of HCl Secretin stimulates liver and pancreas Cholecystokinin stimulates pancreas, gallbladder, and hepatopancreatic sphincter Copyright 2010 Pearson Education, Inc. Other Hormone-Producing Structures Kidneys Erythropoietin signals production of red blood cells Renin initiates the renin-angiotensin mechanism Skin Cholecalciferol, the precursor of vitamin D Adipose tissue Leptin is involved in appetite control, and stimulates

increased energy expenditure Copyright 2010 Pearson Education, Inc. Other Hormone-Producing Structures Skeleton (osteoblasts) Osteocalcin prods pancreatic beta cells to divide and secrete more insulin, improving glucose handling and reducing body fat Thymus Thymulin, thymopoietins, and thymosins are involved in normal the development of the T lymphocytes in the immune response Copyright 2010 Pearson Education, Inc. Developmental Aspects

Hormone-producing glands arise from all three germ layers Exposure to pesticides, industrial chemicals, arsenic, dioxin, and soil and water pollutants disrupts hormone function Sex hormones, thyroid hormone, and glucocorticoids are vulnerable to the effects of pollutants Interference with glucocorticoids may help explain high cancer rates in certain areas Copyright 2010 Pearson Education, Inc. Developmental Aspects Ovaries undergo significant changes with age and become unresponsive to gonadotropins; problems associated with estrogen deficiency begin to occur Testosterone also diminishes with age, but

effect is not usually seen until very old age Copyright 2010 Pearson Education, Inc. Developmental Aspects GH levels decline with age and this accounts for muscle atrophy with age TH declines with age, contributing to lower basal metabolic rates PTH levels remain fairly constant with age, but lack of estrogen in older women makes them more vulnerable to bone-demineralizing effects of PTH Copyright 2010 Pearson Education, Inc.

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