The Endocrine System

1. The Endocrine System Chapter 18

2. Comparison of NS and ES, table 18.1 • Nervous & Endocrine Systems coordinate functions of all body systems: the neuroendocrine system • ________________________ • nerve impulses conducted along axons of neurons • at synapse nerve impulses trigger release of mediator molecules = _____________________ • _______________________ • releases mediator molecules = ________________ • molecules leave glands  blood • circulating blood delivers hormones to virtually all cells • hormones affect only cells with the proper receptor

3. Nervous system Neurotransmitters Act close to release site Muscles, glands, neurons Onset of action within milliseconds Duration of action is generally brief Lasting milliseconds Endocrine system Hormones Act far from release site Cells throughout body Onset of action: seconds to hours, to days Duration of action is generally longer Lasting second to days Comparison of control by NS & ES

4. Exocrine vs. Endocrine • ______________________ • Exocrine glands secrete products into ducts that carry secretions into: • Body cavities • Into the lumen of an organ • Outer surface of the body • Sweat, oil, mucous, digestive • ______________________ • Endocrine glands secrete products (hormones) into interstitial fluid surrounding secretory cells rather than ducts • From interstitial fluid blood(or directly to)  target cells

5. Fig.18.01

6. Functions of hormones fig 18.1 • Help ________________: • Chemical composition & volume of internal environment (interstitial fluid) • Metabolism and energy balance • Contraction of smooth & cardiac muscle fibers • Glandular secretions • Some immune system functions • ____________________________ • Regulate reproductive system • Help establish ____________________

7. Hormones • ___________- secretion of endocrine cells, alters physiological activity of ______________ • approximately 50 hormones • each affects only a few cell types • cell will only respond if has specific receptor for hormone • have powerful effects in low concentrations • Hormones travel through body in the blood • bind receptors on target cell • various target cells respond differently to same hormone • If excess hormone present, receptors may  = _______________________

8. Circulating vs. local hormones • _____________________- most endocrine are this type, circulate in the blood • From secretory cells  interstitial fluid  blood • _______________- act on neighbor or same cell that secreted it, without entering blood • ________________- beside or near • ________________- self

9. Fig.18.02

10. Response to hormone • Various target cells– ______________________________________ • Ex.) insulin: • stimulates synthesis of glycogen in liver cells • stimulates synthesis of triglycerides in adipose cells • Responses are: • _____________________ • _______________________________ • _______________________________ in or out • _________________________ • _________________________

11. Chemical classes of hormones, table 18.2 • ____________________ • Steroid hormones- derived from cholesterol • Thyroid hormones- T3 and T4 • Nitric oxide (NO)- hormone and neurotransmitter • ____________________ • Amine hormones- catecholamines, histamine, seratonin, melatonin • Peptide hormones- some have carb glycoprotein hormones • Eicosanoid hormones- important local, may circ • prostaglandins • leucotrienes

12. Lipid solublefig. 18.3

13. Water solubleFigure 18.4

14. Control of secretion • Release usually in ________________ • Regulation __________________ production • Hormone secretion regulated by: • ______________________________ • ______________________________ • ______________________________ • Most regulation works by feedback loops • Negative feedback loop, 18.17 • Positive feedback loop, 1.4

15. Negative feedback • Ex.) Glucocorticoids

16. Positive feedback • Ex.) Oxytocin

17. Hypothalamus & pituitary gland, 18.5 • ___________________- “master” endocrine gland • secretes hormones that control other endocrine glands • __________________- major link between NS & ES • important regulatory center in NS- can control pituitary • crucial endocrine gland • Cells of hypothalamus synthesize 9 different hormones • 2 of these are stored and secreted from the posterior pit. • Anterior pituitary secretes 7 hormones • Together these16 hormones play important roles in • ______________________________________________

18. Hypothalamus endocrine function • At least 9 hormones synthesized by hypothalamus • 5 releasing & 2 inhibiting hormones produced affect _____________________ (___________________) • produced by hypothalamic neurosecretory cells • transported within axon & released from axon terminals • diffuse hypophyseal portal system 1° 2° plexus  target cells of anterior pituitary • GHRH, GHIH, TRH, GnRH, PRH, PIH, CRH

19. Hypothalamic function (2) • Neurosecretory cells w/cell body in hypothalamus synthesize the 2 hormones that __________________ ______________ (___________________) where the axon terminals lie • package into secretory vesicles • travel to axon terminal and stored • released from posterior pituitary due to nerve impulse triggering exocytosis  capillary plexus • Oxytocin and Anti-diuretic hormone (ADH)

21. Regions of the pituitary gland • Anterior pituitary -75% of total wgt of gland • Pars distalis, pars tuberalis- sheath around infundibulum • Adeno= ________, hypophysis = __________________ • Secretes hormones that reg. wide range • release _______________________ & suppressed ______________________________________ • controlled by negative feedback loops • Posterior pituitary – only oxytocin and ADH • Contains axons & axon terminals of >10,000 neurons from nuclei in hypothalamus • Terminals associated w/ pituicytes- specialized neuroglia • Pars nervosa, infundibulum • ________________________________________________ • Pars media = atrophies during fetal development

22. Hypophyseal portal system • _______________________- blood flows from one capillary network into portal vein & then to 2nd capillary network without passing thru heart • Hypophyseal portal system- blood flows from capillaries in hypothalamus into portal vein that carries blood to capillaries of adenohypophysis • Neurosecretory cells synthesize releasing & inhibiting hormones in cell bodies  vesicles  axons  1° plexus • Act immediately on anterior pituitary before diluted or destroyed in general circulation

23. 5 releasing hormones of hypothalamustable 18.3 • Growth hormone releasing hormone (GHRH) = somatocrinin • Stimulates somatotrophs • Thyrotropin releasing hormone (TRH) • Stimulates thryotrophs AND lactotrophs • Gonadotrophic-releasing hormone (GnRH) • Stimulates gonadotrophs • Prolactin releasing hormone (PRH) • Stimulates lactotrophs • Corticotropin-releasing hormone (CRH) • Stimulates corticotrophs

24. 2 inhibiting hormones of hypothalmustable 18.3 • Growth hormone Inhibiting hormone (GHIH) = Somatostatin • released from hypothalamus inhibits activity of somatotrophs • Prolactin Inhibiting hormone (PIH) = dopamine • inhibits activity of lactotrophs

25. Cells of the Anterior Pituitary • ____________________ – “somato” = body, “tropin” = change • secrete ___________________________ (hGH) or somatotropin • Stimulates several tissues to secrete insulin-like growth factors- • general body growth • regulate metabolism • ___________________ - secrete thyroid stimulating hormone (TSH) or thyrotropin • controls secretions & activities of thyroid gland

26. Cells of the anterior pituitary (2) • _______________-- “gonado” = seed • Secretes _________________________ (FSH) • Stimulates estrogen production in ovaries • Initiates oocyte development • Sperm production • Secretes _________________________ (LH) • Stimulates secretion of progesterone & estrogen in ovaries • Stimulates ovulation, formation of CL • Stimulates secretion of testosterone in testes • Stimulates interstitial cell development in testes

27. Cells of the anterior pituitary (3) • __________________- “lacto” = milk • Secrete prolactin (PRL) • initiating milk production in mammary glands • __________________ - “cortico” = rind or bark • Secrete adrenocorticotropic hormone (ACTH) or corticotropin • Stimulates the adrenal cortex to secrete glucocorticoids • Ex.) cortisol • Some corticotrophs - remnants of pars intermedia secrete melanocyte stimulating hormone (MSH) • Role unclear • May affect brain activity •  levels cause skin darkening

28. Negative feedback – corticotrophs

29. 7 Anterior pituitary hormones & what they stimulate • hGH- stimulates liver, muscle, cartilage, bone, & others to synthesize & secrete IGFs • IGF - promote body cell growth, protein synthesis, tissue repair, lipolysis &  blood glucose • TSH- stimulates synthesis & secretion of thyroid hormones by thyroid gland • T3 and T4 -  BMR, stimulate protein synthesis,  use of glu & f.a. for ATP syn, lipolysis, cholesterol secretion,  body growth, development of NS

30. Anterior pituitary hormones (2) • FSH- follicle stimulating hormone: • ♀- initiate _____________________, induce ovarian secretion of ________________ • ♂- stimulates testes to ____________________ • LH- luteinizing hormone • ♀- stimulates secretion of _______________ & __________________, ______________, & ___________________________________ • ♂ stimulates ___________________ production

31. Anterior pituitary hormones (3) • PRL - promotes milk secretion by mammary glands • ACTH – • stimulates secretion of ___________________ (for glucose metabolism) by adrenal cortex • ____________________ • MSH- exact role unknown, may influence brain activity, when present in excess can cause darkening of skin

33. 2 Posterior pituitary hormones, table 18.5 • ____________________ (OT)- • stimulates uterine smooth muscle contraction during childbirth • stimulates contraction of myoepithelial cells in mammary glands  milk ejection • Pitocin is synthetic form • _______________________ (ADH) or vasopressin- • Anti = against, dia= throughput, ouresis = urination • conserves body water by decreasing urine volume • decrease water loss thru perspiration • raises bp by constricting arterioles

36. Thyroid hormones, table 18.6 & fig 18.10 • T3 (_________________) and T4 (____________)- •  BMR • ↑ O2 consumption, metabolism of carbs, fats, protein ↑ • Stimulate synthesis of Na+/K+ pump • ↑ ATP production ↑ more heat ↑ body temp: calorigenic • Stim protein synthesis &  glucose & fa use to make ATP • ↑ lipolysis & enhance cholesterol excretion in bile • Enhance actions of catecholamines (NE and E) • ↑ heart rate, ↑ b.p. • Accelerate body growth (w/ hGH & insulin) • contribute to development of nervous & skeletal systems

37. Also a hormone produced in the thyroid: • __________________ (CT)- parafollicular C cells of the thyroid produce it • lowers blood levels of calcium & phosphates • Inhibits bone reabsorption by osteoclasts & accelerating uptake of calcium & phosphates into bone matrix • High blood calcium levels stimulate secretion • (low blood calcium levels inhibit secretion)

40. Formation, storage & release of T3 & T4, figures 18.11 and 18.12 • Thyroid = only gland that stores large quantities of its secretory product • 100 day supply in colloid • Figure 18.11 shows synthesis • Figure 18.12 shows control of secretion: • TRH from hypothalamus  anterior pituitary causes releases TSH  thyroid gland causes release of T3 & T4  negative feedback inhibition of both TRH & TSH

42. Thyroid problems • Deficiencies in thyroid hormones during fetal development, infancy or childhood causes: • Severe mental retardation • Stunted bone growth • ______________________ symptoms include: • ↑ heart rate, ↑b.p.,  force of heart beats • Removal of thyroid- __________________ _____________________ because cannot utilize calorigenic effect

43. Parathyroid gland hormones • _______________________ (PTH)- • Specifically works by  # & activityof _____________ •  bone resorption, releasing ionic Ca2+ & phosphates • In the _________________: • Slows Ca2+ & Mg2+ loss to urine •  phosphate loss from blood to urine • promotes formation of calcitriol by kidneys • Calcitriol = active form Vitamin D •  absorption rate of dietary Ca2+ , Mg2+ ,& phosphates • Blood Ca2+ directly controls _______________ (from thyroid gland) & PTH secretion via negative feedback

45. Adrenal glands = suprarenal glands • CT capsule cover, highly vascularized (like thyroid) • Adrenal ___________ – 80-90% of gland, peripheral • Produces steroid hormones essential for life • Loss would lead to death due to dehydration & electrolyte imbalance (few days to week) unless HRT • Adrenal ____________ – centrally located • Produces 3 _____________________ • Norepinephrine • Epinephrine • Dopamine (small amount) • Modified sympathetic ganglion of the ANS

47. Adrenal cortex hormones • ______________ (mainly aldosterone) - affect mineral homeostasis, in zonula glomerulosa • ↑ blood levels of Na+ & water •  decrease blood levels of K+ • _______________________ promotes excretion of H+ in urine • Removing acids  preventing acidosis

49. Adrenal cortex hormones • __________________ -95% _____________ = hydrocortisone, corticosterone, & cortisone, zona fasciulata • affect glucose homeostasis, • Regulate metabolism & resistance to stress • ↑ protein breakdown (except in liver) • stimulate gluconeogenesis in liver & lipolysis • provides resistance to stress • Glucose at liver provides source of ATP to combat stresses: • Exercise, fasting, Symp NS, temp∆, high altitude, bleeding, infection, surgery, trauma, disease • Raise bp- advantageous during blood loss •  inflammation & depress immune responses