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Chapter 17– The Endocrine System

Chapter 17– The Endocrine System. Ch. 17 Endocrine-- Study Guide. Critically read pp. 638-658 before “Hormones and Their Actions” section pp. 668-677 “Endocrine Disorder” section Do Before You Go On and Think About It questions in the textbook

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Chapter 17– The Endocrine System

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  1. Chapter 17– The Endocrine System

  2. Ch. 17 Endocrine-- Study Guide Critically read pp. 638-658 before “Hormones and Their Actions” section pp. 668-677 “Endocrine Disorder” section Do Before You Go On and Think About It questions in the textbook Do Testing Your Recall— 1-4, 6, 8, 11, 13, 15-18 Do True or False– 1, 3-10 Do Testing Your Comprehension-- none

  3. 17.1. Overview of the Endocrine System

  4. Fig. 17.1--Endocrine glands

  5. § Overview of Cell Communications • Necessary for integration of cell activities • Mechanisms • gap junctions • pores in cell membrane allow signaling chemicals to move from cell to cell; Example-- • Neurotransmitters (Fig. 17.2 (a)) • released from neurons to travel across gap to 2nd cell; Examples-- • Paracrine (local hormones) • secreted into tissue fluids to affect nearby cells • Hormones (strict definition) • chemical messengers that travel in the bloodstream . . .

  6. Figure 17.2a– A neuron has a long fiber that delivers its neurotransmitter.

  7. § Endocrine System Components • Endocrine system • endocrine organs (thyroid, pineal, etc) • hormone producing cells in organs (brain, heart and small intestine) • Endocrine glands • produce hormones • Hormone • chemical messenger secreted into bloodstream, stimulates response in another tissue or organ (Fig. 17.2b); How? • Target cells • have receptors for a specific hormone 17-7

  8. Figure 17.2b– Endocrine cells secrete a hormone into the bloodstream. 17-8

  9. § Comparison of Nervous& Endocrine Systems I (major differences) • Communication • nervous sys.- both electrical and chemical • endocrine sys.- • Speed and persistence of response • nervous sys.- reacts quickly (1 - 10 msec), stops quickly • endocrine sys.- • Adaptation to long-term stimuli • nervous sys.- response declines (adapts quickly) • endocrine sys.- response persists 17-9

  10. § Comparison of Nervous& Endocrine Systems II (Similarities) • Several chemicals function as both hormones and neurotransmitters • NE and ADH • Some hormones secreted by neuroendocrine cells (neurons) • oxytocin • Both systems with overlapping effects on same target cells • NE and glucagon cause glycogen hydrolysis in liver • Systems regulate each other • neurons trigger hormone secretion • hormones stimulate or inhibit neurons 17-10

  11. § Endocrine vs. Exocrine Glands • Exocrine glands • ducts carry secretion to a surface or organ cavity • extracellular effects (food digestion) • Example-- • Endocrine glands • no ducts; • intracellular effects, alter target cell metabolism • Example 17-11

  12. 17.2A. The Hypothalamus and Pituitary Gland 17-12

  13. § Hypothalamus • Shaped like a flattened funnel, forms floor and walls of third ventricle (Fig. 14.12b) • Regulates primitive functions from water balance, sex drive, . . . • Regulate many functions carried out by pituitary gland 17-13

  14. Pineal gland Hypothalamic Nuclei Anterior nucleus Thirst; thermoregulation Regulates appetite: secretes releasing hormones that regulate anterior pituitary Arcuate nucleus leaves Dorsomedial nucleus Rage and other emotions Mammillary nuclei Relay between limbic system and thalamus; involved in long- term memory Paraventricular nucleus Produces oxytocin (involved in childbirth, lactation, orgasm); controls posterior pituitary Posterior nucleus Functions with periaqueductal gray matter of midbrain in emotional, cardiovascular, and pain control Hormonal control of reproductive functions Preoptic nucleus Suprachiasmatic nucleus Biological clock; regulates circadian rhythms and female reproductive cycle Pituitary gland Produces antidiuretic hormone (involved in water balance); controls posterior pituitary Supraoptic nucleus Satiety center (suppresses hunger) Ventromedial nucleus (b) Hypothalamus

  15. § Pituitary Gland (Hypophysis) • Suspended from hypothalamus by stalk (infundibulum) • Location and size • housed in sella turcica of sphenoid bone • 1.3 cm diameter • Adenohypophysis (________ pituitary) • arises from hypophyseal pouch (outgrowth of pharynx); Fig. 17.3 • Neurohypophysis(________ pituitary) • arises from brain 17-15

  16. 17-16

  17. § Hypothalamic-hypophyseal portal system--1 • (Anatomy)--Hypothalamic hormones travel in portal system from hypothalamus to anterior pituitary (Fig. 17.4 and x) • Primary capillaries--? • Secondary capillaries--? • (Physiology) Hypothalamic hormones regulate hormones secretion by anterior pituitary • Example— Gonadotropin-releasing hormone (GnRH) and FSH/LH

  18.  

  19. Neurosecretory neurons Hypothalamus Hypophysiotropic H.: ●● 1 Systemic arterial inflow 2 Anterior pituitary Hypothalamic-hypophyseal portal system 3 6 System venous outflow 4 Posterior pituitary 5 • Anterior pituitary hormones:

  20. § Hypothalamic-hypophyseal portal system--2 • Advantages (of this portal system)— • Almost all the blood supplied to the anterior pituitary must first pass through the __________________________ • Releasing/inhibiting hormones then can directly deliver to the anterior pituitary in what fashion ? ____________________________

  21. Check Point Questions-- • Besides hormones, give another way for intercellular communication. • Give an example of a hormone. Why does your example qualify as a hormone? (hint: definition of hormone) • Give an example of a hypothalamic hormone. • What is the target tissue of a hypothalamic hormone secreted into the hypothalamic-hypophyseal portal system?

  22. § Hormones secreted by anterior pituitary • FSH(follicle stimulating hormone) • LH(luteinizing hormone) The above two are called gonadotropins • TSH(thyroid stimulating hormone) • ACTH(adrenocorticotropic hormone) • GH (growth hormone) • PRL(prolactin) • Tropic hormones-- target other endocrine glands to release their own hormones; which ones above? (Fig. 17.6)

  23. 3. 2. 1.

  24. § The Posterior Pituitary

  25. § Posterior Pituitary Hormones • OT (oxytocin) and ADH • produced in hypothalamus • transported by hypothalamo-hypophyseal tract to posterior lobe (stores/releases hormones)

  26. Hormone Actions: Posterior Lobe • ADH (Antidiuretic Hormone) • Target organ/tissue-- ? •  water retention, reduce urine • also functions as neurotransmitter • Oxytocin • labor contractions, lactation (milk ejection) • possible role in • sperm transport . . . • emotional bonding • Table 17.4 on p. 645 is important

  27. Regulation of Posterior Pituitary • Posterior lobe control - neuroendocrine reflexes • hormone release in response to nervous system signals • suckling infant stimulates nerve endings  hypothalamus  posterior lobe  oxytocin milk ejection • hormone release in response to higher brain centers • milk ejection reflex can be triggered by a baby's cry

  28. 17.2B. Control of Pituitary Secretion 17-28

  29. § Negative feedback • Principle– Def. The body senses a change and activates mechanisms that negate it; • (On pituitary hormones) target organ hormone levels inhibits release of tropic hormones • Example– TRH-TSH-thyroid hormones (see next slide; Fig. 17.7) 17-29

  30. (▬)

  31. § Positive feedback—1 • Definition– change in a factor triggers a physiological response that AMPLIFIES an initial change • Example— in the birth of a baby; how? Fig. 1.12

  32. § Positive feedback—2 • Details of birth of a baby • 1. Uterine contractions push the fetus against the cervix • 2. The stretching of the cervix (RECEPTOR/SENSOR is the nerve cells here) triggers nerve impulses to the brain • 3. Brings about oxytocin secretion • 4. The hormone oxytocin causes even STRONGER powerful contractions of the uterus (EFFECTOR is muscles in wall of uterus)

  33. 17.3. Other Endocrine Glands 17-34

  34. § A--Pineal Gland • Where is it? • Peak secretion ages 1-5; by puberty 75% lower • Produces serotonin by day, converts it to __________ at night • May regulate timing of puberty in humans • Melatonin  in SAD;  by phototherapy • Symptoms of SAD: depression . . . • More SAD patients in Alaska or Florida? • Premenstrual syndrome (PMS) similar to SAD 17-35

  35. § B--Thymus • Location-- mediastinum, • Involution after puberty • Its hormones--thymopoietin and thymosins; • Functions– on T-lymphocytes 17-36

  36. § C--Thyroid Gland-1 • Largest endocrine gland; high rate of blood flow • Location--Anterior and lateral sides of trachea Fig. 17.9a 17-37

  37. Thyroid Gland-2 • Histology— • Thyroid follicles (Fig. 17.9, Fig. x ) • Filled with colloid and lined with simple cuboidal epithelial (follicular cells) that secretes two thyroid hormones (TH), • Triiodothyronine Thyroxine • Control of TH secretion is in response to another hormone from the pituitary called ____________ 17-38

  38. 17-39

  39. 17-40

  40. Thyroid Gland--3 • Functions of thyroid hormone •  or ↓ (circle one)body’s metabolic rate and O2 consumption • Calorigenic effect – •  or ↓ (circle one)heart rate and contraction strength •  respiratory rate • stimulates appetite and breakdown CHO, lipids for fuel 17-41

  41. Thyroid Gland--4 • C (calcitonin or parafollicular) cells • Where are they located? Fig. x • Produce __________ • Target organ--? • Function--  blood Ca2+, promotes Ca2+ deposition and bone formation especially in children • Osteoblasts more active • Osteoclasts are inhibited 17-42

  42. 17-43

  43. 17-44

  44. § D--Parathyroid Glands--1 • Location— • Secretion— parathyroid hormone (PTH) • Target organs--? 17-45

  45. § Parathyroid Glands--2 • Functions of PTH-- •  or ↓ (circle one) blood Ca2+ levels • promotes synthesis of calcitriol which: • +/-- absorption of Ca2+ • +/-- urinary excretion • +/-- resorption of bone matrix 17-46

  46. § E— The Pancreas-1 • Location— in relation to the stomach (Fig. 17.12a-b, Fig. x) • Endocrine secretion— by pancreatic islets • Only constitute about ____ of the pancreas • Including insulin, glucagon, and somatostatin • Which one is hyperglycemic hormone and which one is hypoglycermic hormone? • 98% is exocrine digestive gland 17-47

  47. 17-48

  48. 1 2 17-49

  49. 17-50

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