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ENDOCRINOLOGY Reading: Chapter 11 1 Neural vs. Endocrine Communication Neural -electrical/hardwired (phone) -fast (msec) -short-term changes -electrical impulse + NT’s -localized action (stim. 1 muscle or gland) RESULT = Endocrine -chemical (mail) -relatively slow -long-term and/or cyclical changes -hormones (dilution, so you need greater sensitivity) -widespread action (many tissues) RESULT = homeostasis reproduction growth 2 Fig. 11.01 3 Fig. 11.02 4 “Neuroendocrine System” The nervous & endocrine systems are very closely intertwined. Hypothalamus (nervous tissue) controls endocrine secretions What chemical is both a neurotransmitter and a hormone? Norepinephrine 5 GENERALIZED ENDOCRINE FUNCTIONS 1. Maintains Homeostasis: Dehydration = Nutrition = Infection = regulate water & electrolyte balance transport across cell membranes, metabolic rate, energy balance, control smooth muscle activity, glands immune system activity 2. Control Reproduction & Development: -Gamete development, ovulation (timing), parturition, lactation -Growth of various tissues -Development (imbalances can impair brain dev.) 6 Hormones: mechanism of action Gland = cluster of epithelial cells that secrete Exocrine Gland = -secretion via DUCT -sweat, mucous, sebaceous, ……. Endocrine Gland = -secretion into BLOOD -so these are highly vascular tissue 7 What is a hormone? A substance secreted by a cell (into the blood), that has an effect on the function of another “target” cell. A “chemical messenger” Two types/groups, divided based on chemical nature. 8 Water Insoluble Hormones • • • • STEROIDS Synthesized from cholesterol, on SER 4 ring structure (C & H) Carried in plasma by carrier proteins Example: sex hormones 9 Water Soluble Hormones • Dissolve in plasma (no carriers needed) Amines: -derived from amino acids (a.a’s) Peptides: -short chains (2 to 12) of a.a’s Proteins: -100 to 200 a.a’s 10 Target Tissues • Target tissues have specific receptors – – – – Receptors = proteins or glycoproteins Each receptor recognizes one hormone But, each cell can have 2000 to 100,000 receptors! More receptors = greater sensitivity to that hormone NOTE: -only tissues w/ receptor are affected -water soluble & insoluble hormones have v. different actions at target tissues 11 Action of Steroids (lipid soluble) a. b. b. c. d. e. f. Steriod hormones attach to carrier proteins in plasma which: -increases solubility -prevents their excretion -creates a reserve Dissociate from carrier to pass through cell membrane Bind w/ new carrier inside cell, usually the nucleus Hormone/carrier complex bind w/ DNA Specific genes = activated Specific proteins are made depending on which genes are activated The newly synthesized protein may change __________ or produce some other effect associated with a particular steriod hormone. PROPORTIONAL RESPONSE 12 13 Action of Water Soluble Hormones 1. Hormones = soluble in plasma (do you need a carrier?) 2. Hormones can’t cross cell membrane 3. So, receptors found on surface of cell 4. H-R complex on cell surface triggers changes inside the cell 5. H-R-receptor binding activates a cascade response inside target cell 6. [Proteins are ________ so that they are capable of activating and inactivating enzymes & produce the effect associated w/ particular _____ hormone. 14 15 Control of Hormonal Secretions Negative Feedback Based On: -amount of hormone produced (thyroxin) -concentration of a product created in response to a particular hormone (blood sugar level) 16 Low Thyroxin (+) Anterior Pituitary TSH (-) Thyroid Thyroxin 17 18 Control of Hormonal Secretions Neural Control: -epinephrine released from adrenal medulla -due to pre-ganglionic stimulation (what branch of the nervous system?) 19 20 Hormonal Interactions Synergistic: 2+ hormones working together Estrogen + progesterone + PL + oxytocin Antagonistic: Effect of 1 hormone opposed by another Insulin opposes the action glucagon 21 Removal of “yesterday’s” hormones Water Soluble Hormones • Do these enter the cell? • Removed/broken down in minutes short term changes • Excreted by _____________ Water Insoluble Hormones • Do these enter the cell? • Why might these stay in the blood longer? • Limited kidney clearance • Mainly removed by ______________ 22 Pituitary Gland (hypophysis) Embryogenesis: Nerve Tissue + Epithelial Tissue 1. Neural portion -floor of diencephalon -grows down to form neural stalk 2. Oral epithelium -making roof of mouth in embryo -a little piece pinches off -wraps around ant. part of neural stalk 23 Pituitary Gland (hypophysis) - located below hypothalamus - has 2 portions: anterior pituitary (adenohypophysis) posterior pituitary (neurohypophysis) 24 Posterior Pituitary -neurohypophysis highly innervated -no “gland cells” -stores and releases ADH & oxytocin, hormones produced by hypothalamus -neurons run from hypothalamus, through infundibulum, to posterior pituitary 25 1) antidiuretic hormone (ADH) -stimulates retention of H2O in the kidneys. -absence of ADH causes diabetes insipidus. 2) oxytocin - stimulates contractions during labor. - stimulates uterus constriction post-partum. - stimulates milk letdown. 26 Anterior Pituitary -adenohypophysis -composed of glandular epithelial tissue -no innervation -no direct blood supply, blood receive via portal vein -produces 6 major hormones -hormones are only released in response to releasing factors from hypothalamus 27 Anterior Pituitary (con’t) -produces 6 major tropic hormones. -tropic hormone act on other tissues to trigger growth, increased activity, or hormone release 28 The 6 Anterior Pituitary Hormones 1) Thyrotropin (troph = to feed or nourish) -also called Thyroid Stimulating Hormone (TSH) -stimulates thyroid to increase in size and activity. 2) Adrenocorticotrophic Hormone (ACTH) - stimulates adrenal cortex to increase in size & activity 3) Prolactin (PL) -stimulates milk production in women -possible electrolyte regulation in men 29 4) Somatotropin = Growth Hormone (GH) -stimulates growth of tissue (bone, muscle, organs) -maintains tissues -produced throughout life, but there is a surge in adolescence -Until age 25 = long bone growth & soft tissue growth -After age 25 = health and repair of soft tissues only 30 Growth Hormone Abnormalities a) b) c) d) Gigantism Acromegaly Dwarfism Abuse in athletes 31 Growth Hormone Abnormalities a) Gigantism: -too much GH before age 25 -tumor in pituitary gland -very tall 32 Growth Hormone Abnormalities Acromegaly: -too much GH after age 25 -growth of soft tissues (nose, chin, hands…) -pituitary gland tumor 33 Growth Hormone Abnormalities c) Pituitary Dwarfism: -insufficient GH 34 Growth Hormone Abnormalities d) Abuse in athletes…why? Effect of age? 35 5 & 6) gonadotrophic hormones a) follicle stimulating hormone (FSH) -stimulates follicles to develop -follicle = ova + surrounding cells (make estrogens & progesterone) -stimulates the production of sperm b) luteinizing hormone (LH) -LH stimulates ovulation in females -in males it stimulates the interstitial cells in testes to make testosterone (in males LH is called ICSH) 36 Hypothalamus - Part of both the nervous & endocrine systems. - Controls pituitary gland w/ releasing & inhibitory factors GHIH decreases GH sec. GHRH increases GH sec. PIH decreases PL sec. PRH increases PL sec. 37 38 ENDOCRINOLOGY Reading: Chapter 11 39 Non-Pituitary Endocrine Glands 1. Adrenal gland - located just above the kidneys. - each gland has 2 separate portions: inside = medulla outside = cortex 40 41 Adrenal Cortex: Mineralocorticoids -primarily aldosterone (steroid) -stimulates the kidneys to retain sodium -controlled by ACTH from ant. Pit. -controlled by kidneys (neg. feedback) aldosterone 42 Adrenal Cortex: Glucocorticoids -mainly cortisol -released during stress (coping mechanism) *increases blood glucose levels *vasoconstriction decreases inflammation *stabilizes lysosomes reduce cell destruction Cortisol (hydrocortisone) 43 Adrenal Cortex: Androgens: -male sex hormones -little effect in males (high testosterone from testes) -stimulate libido & muscle development in females Androgens 44 Adrenal Cortex: Abnormalities: -excess androgens = masculinization in females (adult vs. fetal) -adrenal failure = Addison’s disease (unable to reg. Na & K) -excess adrenal activity = Cushing’s syndrome -too much cortisol = fat storage in face & on back 45 Adrenal Medulla -stimulated by ANS -E &small quantities of NE are released Epinephrine Norepinephrine 46 2. Thyroid Gland - located just below the larynx. - Produces 2 major hormones = thyroxin & thyrocalcitonin. 47 a) Thyroxin -a metabolic hormone -made when iodine is available -increases BMR & ATP production/use -increases oxygen consumption -increases rate of heat production -stimulates protein synthesis -works permissively w/ GH & insulin to accelerate growth 48 Low Thyroxin (+) Hypothalamus (-) TRH Anterior Pituitary (-) TSH Thyroid Thyroxin 49 b) calcitonin (thyrocalcitonin) -stimulates osteoblast activity -lowers blood calcium levels 50 Abnormalities of the thyroid gland: 1) hypothyroidism -insufficient activity of thyroid -decreased metabolic rate -sluggish & tiered -cretinism in infants (abnormal NS dev.) -diagnose with low thyroxin & high TSH -treat with thyroxin 51 Abnormalities of the thyroid gland: 2) hyperthyroidism -increased metabolic rate. -weight loss, nervousness, insomnia -exophtalmia -treat with surgery or iodine blockers 52 Abnormalities of the thyroid gland: 3) goiter -enlarged thyroid -many causes, including lack of iodine -treat with iodine & cosmetic surgery 53 3) parathyroid glands usually 4 glands located on the dorsal surface of the thyroid. produce parathyroid hormone (PTH, or parathormone) PTH stimulates osteoclast (bone eaters) activity Stimulate calcium retention by kidneys & intestines raises blood Ca - 54 55 4) Pancreas - Located next to stomach & duodenum. Has exocrine and endocrine functions. Endocrine tissue = Islets of Langerhans. 2 major hormones: glucagon and insulin. 56 Glucagon -produced by alpha cells in the islets -released when blood glucose levels fall (hypoglycemia) -causes breakdown of glycogen, glucose rel. from tissues -blood glucose returns to normal levels Glucagon 57 Insulin -produced by beta cells in the islets -released when blood glucose levels rise (hyperglycemia) -causes glucose to move into cells -lowers blood glucose levels -glucose is stored in the liver & muscle as glycogen (glycogenesis) Insulin 58 59 Diabetes Mellitus • • • • • • • • • • Type I Juvenile onset (under age 25) Insulin dependant Usually sudden onset Autoimmune destruction of beta-cells ~10% of all diabetics Family history is rare “Starvation” of cells Body uses fat for energy Leads to ketoacidosis & coma Long-term: renal & retinal problems, hypertension, arteriosclerosis, gangrene • • • • • • • • Type II Adult onset ????? NOT insulin dependant Usually gradual onset Lack insulin receptors at target cells ~90% of all diabetics Strong links within family Treated with drugs to stimulate insulin secretion Also with diet & exercise 60 5) pineal gland - located near the midbrain produces melatonin important for seasonal breeding in humans it is important for sleep-wake cycles increased light decreased melatonin 61 6) Thymus -located just below sternum -large in children but atrophies in adults -produces thymosin stimulates the immune system Thymosin 62 7) Gonads -ovaries in women (estrogens & progesterone) -testes in men (testosterone) Testosterone Estrogens Progesterone 63 Do endocrine organs have other functions? Most often, YES! Give me some examples: 64 8) Prostaglandins -hormone like chemicals produced by most cells -important in inflammation, clotting, BP, uterine contractions and many other functions -inhibited by ibuprofen 65 END 66