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Endocrine System A. Endocrine glands B. Comparison of nervous and endocrine systems C. Hormones 1. Hormone receptors 2. Circulating and local hormones D. Mechanisms of hormone action 1. Activation of intracellular receptors 2. Activation of plasma membrane receptors E. Control of hormonal secretions F. Hypothalamus and pituitary gland (hypophysis) 1. Anterior pituitary gland (adenohypophysis) a. Human growth hormone b. Thyroid-stimulating hormone c. Follicle-stimulating hormone d. Luteinizing hormone e. Prolactin f. Melanocyte-stimulating hormone g. Adrenocorticotropic hormone 2. Posterior pituitary gland (neurohypophysis) a. Oxytocin b. Antidiuretic hormone G. Thyroid gland 1. Formation, storage, and release of thyroid hormones 2. Actions of thyroid hormones 3. Control of thyroid hormone secretion 4. Calcitonin H. Parathyroid glands 1. Parathyroid hormone I. Adrenal (suprarenal) glands 1. Adrenal cortex a. Mineralocorticoids b. Glucocorticoids c. Gonadocorticoids 2. Adrenal medulla a. Epinephrine and norepinephrine J. Pancreas 1. Glucagon 2. Insulin K. General adaptation syndrome Endocrine Glands Endocrine vs. exocrine Hormone Endocrine gland Nervous System Versus Endocrine System Together, the nervous and endocrine systems coordinate functions of all body systems. NERVOUS ENDOCRINE neurotransmitters hormones muscle contractions and glandular secretions metabolic activities of cells acts in milliseconds acts in seconds to minutes to hours to days to months brief effects long-lasting effects Hormone Receptors 1. 2. 3. 4. target cells receptors down-regulation up-regulation Hormone Interactions 1. synergistic effects 2. permissive effects 3. antagonistic effects Types of Hormones 1. circulating -- hormones 2. local – paracrines, autocrines Mechanisms of Hormone Action 1. lipid-soluble hormones a. steroid and thyroid hormones b. use intracellular receptors 2. water-soluble hormones a. catecholamine, peptide, and protein hormones b. use membrane-bound receptors c. and second messengers Lipid Soluble Hormones 1. intracelluar receptors 2. hormone-receptor complex 3. altered gene expression Steroid Hormone Action Water Soluble Hormones 1. membrane-bound receptors 2. first messenger vs second messenger 3. adenylate cyclase and cyclic AMP 4. phosphodiesterase Water soluble hormones and Cyclin AMP as a 2nd Messenger 2nd Messenger Systems Control of hormonal secretions = negative feedback hyperglycemia = insulin secretion 110 mg% [glucose] steady state 90 mg% hypoglycemia = glucagon secretion time Hypothalamus and Pituitary Gland Hypothalamus 1. master control 2. major integrator Pituitary gland (hypophysis) 1. infundibulum 2. sella turcica hypothalamus infundibulum pituitary gland sella turcica in sphenoid bone Hypothalamus-Master Controller Pituitary Gland 1. anterior pituitary a. derived from Rathke's pouch b. connected to hypothalamus by hypophyseal portal system (Rathke’s pouch) 2. posterior pituitary a. outgrowth of hypothalamus b. contains pituicytes c. connected to hypothalamus by nerve tract Anterior Pituitary (adenohypophysis) 1. releasing vs inhibiting factors 2. hypophyseal portal system superior hypophyseal arteries primary plexus of capillaries hypophyseal veins secondary plexus of capillaries anterior hypophyseal veins The seven hormones secreted by the anterior pituitary gland growth hormone (GH) thyroid-stimulating hormone (TSH) follicle-stimulating hormone (FSH) luteinizing hormone (LH) adrenocorticotropic hormone (ACTH) prolactin (PRL) melanocyte-stimulating hormone (MSH) Tropic Hormones FSH LH TSH ACTH Growth Hormone Promotion of secretion Regulation of secretion 1. HYPOGLYCEMIA (low blood sugar) 2. decreased blood fatty acids 3. increased blood amino acids 4. deep sleep hypoglycemia hyperglycemia inhibits GH-IF secretion Inhibits GH-RF secretion HYPOTHALAMUS Inhibition of secretion 1. HYPERGLYCEMIA (high blood sugar) 2. 3. 4. 5. 6. increased blood fatty acids decreased blood amino acids REM sleep obesity severe emotional states GH-RF GH-IF secretion on ANTERIOR PITUITARY GLAND growth hormone Actions 1. increased cellular uptake of amino acids = increased protein synthesis = growth/maintenance 2. increased lipolysis and gluconeogenesis for energy, leading to hyperglycemia = diabetogenic effect secretion off Growth Hormone Acromegaly Thyroid Stimulating Hormone decreased basal metabolic rate (BMR) ( -) increased hypothalamic TSH-RF secretion negative feedback increased anterior pituitary TSH secretion increased thyroid gland T3 and T4 secretion increased basal metabolic rate Follicle Stimulating Hormone - male decreased inhibin secretion ( -) increased hypothalamic Gonadotropin-RF secretion negative feedback of inhibin increased anterior pituitary FSH secretion 1. increased sperm formation (spermatogenesis) 2. increased activity of Sertoli cells (spermiogenesis) 3. increased inhibin secretion by Sertoli cells Follicle Stimulating Hormone-Female decreased estrogen secretion ( -) negative feedback of rising estrogen increased hypothalamic Gonadotropin-RF secretion increased anterior pituitary FSH secretion 1. directly stimulates egg formation by ovaries 2. as a result, ovaries produce estrogen Luteinizing Hormone- male decreased testosterone secretion ( -) negative feedback of rising estrogen increased hypothalamic Gonadotropin-RF secretion increased anterior pituitary LH secretion stimulates testosterone secretion by interstitial cells (of Leydig) in testes Luteinizing Hormone- female increased estrogen secretion ( -) negative feedback of dropping estrogen increased hypothalamic Gonadotropin-RF secretion increased anterior pituitary LH secretion 1. directly stimulates ovulation 2. as a result, estrogen levels drop until corpus luteum is formed Adrenocorticotropic Hormone increased stress increased hypothalamic Corticotropin-RF secretion ( -) negative feedback of decreasing stress increased anterior pituitary ACTH secretion 1. 2. 3. 4. increased alertness increased blood pressure increased blood glucose anti-inflammatory actions decreased stress Prolactin-Female inhibition pathway increased blood estrogen stimulation pathway decreased blood estrogen + postpartum suckling reflex hypothalamic PRL-IF secretion hypothalamic PRL-RF secretion decreased or no PRL secretion from anterior pituitary gland anterior pituitary gland PRL secretion milk synthesis by postpartum mammary glands Posterior Pituitary (neurohypophysis) 1. 2. 3. 4. not really endocrine pituicytes hypothalamic nuclei hypothalamohypophyseal tract 5. hormones a. oxytocin b. antidiuretic hormone Oxytocin 1. neuroendocrine reflex 2. uterine contractions 3. myoepithelial cells of mammary glands ANTI-DIURETIC HORMONE 1. 2. 3. 4. aka = vasopressin, ADH hypothalamic osmoreceptors water reabsorption by kidneys diabetes insipidus dehydration increased interstitial fluid osmotic pressure ( -) stimulation of hypothalamic osmoreceptors secretion of ADH from posterior pituitary gland 1. WATER REABSORPTION BY KIDNEYS 2. decreased perspiration increased water in blood increased interstitial fluid osmotic pressure Also leads to increase in BP ADH actions Thyroid Gland 1. 2. 3. 4. 5. location follicles follicular cells triiodothyronine (T3) tetraiodothyronine (T4, thyroxine) _____________________ 6. parafollicular (C-) cells 7. calcitonin Thyroid Hormone Secretion 1 tyrosine 1. 2. 3. 4. 5. stores secretory product captures iodide ions thyroglobulin tyrosine colloid thyroglobulin colloid blood capillary thyroid follicle follicle cell 2 colloid I I parafollicular cells blood capillary 3 I I I I I iodinated tyrosines on thyroglobulin (T3) thyroid hormone secretion I colloid T3 follicular cell T3 I cleavage colloid I I I pinocytosis I Thyroid Hormone Synthesis, Storage and Secretion Endemic Goiter- Iodine deficiencylack of thryoid hormone Thyroxine Actions and Control 1. TSH stimulation 2. actions a. increased carbohydrate catabolism b. increased fat catabolism c. increased protein anabolism d. net result = increased BMR __________________________________ 3. normal growth and development (nervous system -- cretinism) Thyroxine decreased basal metabolic rate increased TSH-RF secretion from hypothalamic neurons ( -) secretion of TSH from anterior pituitary gland ( -) secretion of T3 and T4 (thyroxine) from thyroid gland follicle cells negative feedback Increased carbohydrate catabolism Increased fat catabolism Increased protein anabolism T3 and T4 (thyroxine) secretion increased basal metabolic rate Negative Feedback Inhibition in Pituitary Thryoid Axis Calcitonin 1. parafollicular (C-) cells 2. hypercalcemia = CT secretion 3. actions a. inhibits osteoclasts b. stimulates osteogenesis c. decreased Ca++ reabsorption 4. result = normocalcemia CALCITONIN and BLOOD CALCIUM REGULATION CONTROLLED CONDITION Normocalcemia (blood calcium = 9.5-10.5mg%) A stress or stimulus causes an increase in blood calcium negative feedback RETURN TO HOMEOSTASIS Increased bone formation results in increased calcium deposition in bone – Return to normocalcemia RECEPTOR Parafollicular cells of thyroid gland recognize hypercalcemia EFFECTORS (blood calcium >10.5 mg% Reduced osteoclast activity Increased osteoblast activity CONTROL CENTER Parafollicular cells secrete calcitonin Parathyroid Hormone 1. 2. 3. 4. a. b. c. 5. location chief cells and oxyphil cells hypocalcemia = PTH secretion actions activate osteoclasts increased Ca++ absorption increased Ca++ reabsorption result = normocalcemia PTH and BLOOD CALCIUM REGULATION CONTROLLED CONDITION Normocalcemia (blood calcium = 9.5-10.5mg%) A stress or stimulus causes a decrease in blood calcium negative feedback RETURN TO HOMEOSTASIS Increased bone breakdown results in increased calcium release to blood – Return to normocalcemia RECEPTOR EFFECTORS Chief cells of parathythyroid glands recognize hypocalcemia Increased osteoclast activity (blood calcium <9.5 mg% Decreased osteoblast activity Increased urine phosphate output Decreased urine calcium output CONTROL CENTER Chief cells secrete PTH Adrenal (suprarenal) glands (2) 1. 2. 3. 4. a. b. c. location cortex vs medulla cortex = steroids medulla = catecholamines sympathetic NS NE and EPI fight-or-flight Adrenal cortex (zona glomerulosa) 1. mineralocorticoids (aldosterone) 2. electrolyte and fluid balance 3. high [K+] = aldosterone secretion or renin-angiotensin system 4. actions a. decreased K+ reabsorption b. increased Na+ reabsorption Aldosterone control via potassium control via renin-angiotensin system hyperkalemia ( -) negative feedback dehydration, Na+ deficiency, hemorrhage aldosterone secretion from zona glomerulosa cells decreased blood volume decreased blood pressure decreased K+ reabsorption by kidneys ( -) renin secretion by kidneys normokalemia negative feedback activation of angiotensin II aldosterone secretion ADH secretion increased thirst increased vasoconstriction increased blood pressure Adrenal cortex (zona fasciculata) 1. glucocorticoids (hydrocortisone, cortisone) 2. stress > C-RF > ACTH > glucocorticoids 3. actions a. promote normal metabolism (glucose availability) b. resistance to stress (alertness, energy, blood pressure) c. anti-inflammatory (stabilizes membranes) Glucocorticoids increased stress or decreased blood levels of glucocorticoids ( -) increased hypothalamic corticotropin-RF secretion ( -) increased anterior pituitary ACTH secretion negative feedback increased adrenal secretion of glucocorticoids promote normal metabolism and ensure glucose availability by: increasing protein catabolism increasing gluconeogenesis increased lipolysis Provide resistance to stress by: increased mental alertness increased energy increased blood pressure Increasing anti-inflammatory activity by: stabilizing cell membranes depressing phagocyte activity decreased capillary permeability (decreased swelling) decreased stress negative feedback Adrenal cortex (zona reticularis) 1. gonadocorticoids a. androgens b. estrogens 2. important in development Endocrine (pancreas) 1. location 2. islets of Langerhans 3. cell types a. alpha cells = glucagon b. beta cells = insulin c. delta cells = somatostatin (GH-IF) d. F cells = digestion Glucagon 1. alpha cells 2. hypoglycemia > glucagon secretion 3. actions a. glycogenolysis b. gluconeogenesis 4. result = normoglycemia hypoglycemia (<90mg%) alpha cells secrete glucagon ( -) negative feedback liver cells: increase glycogenolysis increased gluconeogenesis increased blood glucose normoglycemia (>90mg%) Insulin 1. beta cells 2. hyperglycemia > insulin secretion 3. activities a. glucose uptake b. glycogenesis c. glycogenolysis d. gluconeogenesis e. lipogenesis 4. result = normoglycemia ______________________ diabetes mellitus hyperglycemia (<110mg%) beta cells secrete insulin ( -) negative feedback increased glucose uptake into body cells increase glycogenesis (skeletal muscle, liver) increased lipogenesis decreased blood glucose normoglycemia (<110mg%) GENERAL ADAPTATION SYNDROME STRESS ALARM hypothalamus C-RF secretion increased sympathetic activity ACTH increased blood pressure norepinephrine epinephrine ----------------------------------------------------------------------------------------------------------------------------- ---RESISTANCE glucocorticoids increased blood pressure continued decreased inflammatory response increased blood glucose altered protein and fat metaoblism ----------------------------------------------------------------------------------------------------------------------------- ---EXHAUSTION decreased immune response + decreased energy reserves decreased resistance to disease hypertension cardiac failure and renal failure DEATH