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ENDOCRINOLOGY Reading: Chapter 11 1 “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 2 Neural vs. Endocrine Communication Neural -electrical/hardwired (phone) -fast (msec) -short-term changes -electrical impulse + NT’s need -localized action (stim. 1 muscle or gland) RESULT = Endocrine -chemical (mail) -relatively slow -long-term and/or cyclical changes -hormones (dilution, so you greater sensitivity) -widespread action (many tissues) RESULT = homeostasis reproduction growth 3 Fig. 11.01 4 Fig. 11.02 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) norepinephrine & epinephrine Peptides: -short chains (2 to 12) of a.a’s –ADH, Oxytocin Proteins: -100 to 200 a.a’s-Parathyroid hormone, PL, LH, FSH, TSH 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. 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 a-neurohypophysis highly innervated b-no “gland cells” c-stores and releases ADH & oxytocin, hormones produced by hypothalamus d-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 a-composed of glandular epithelial tissue b-no innervation c-no direct blood supply, blood receive via portal vein d-produces 6 major hormones e-hormones are only released in response to releasing factors from hypothalamus 27 Anterior Pituitary (con’t) f-produces 6 major tropic hormones. g-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 5. follicle stimulating hormone (FSH) -stimulates follicles to develop -follicle = ova + surrounding cells (make estrogens & progesterone) -stimulates the production of sperm 6. 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 NSdev.) -diagnose with low thyroxin & highTSH -treat with thyroxin 51 Abnormalities of the thyroid gland: 2) hyperthyroidism -increased metabolic rate. -weight loss, nervousness,insomnia -exophtalmia-bulging eyes -treat with surgery – 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