1. Anatomy and Physiology: The Endocrine System

2. Overview Endocrine System Overview
Hormone Secretion/Pos. & Neg. Feedback
Hypothalamus and Anterior Pituitary
Posterior Pituitary
Thyroid Gland
Parathyroid Glands
Adrenal Cortex
Pancreas
Gonads
Pineal Gland

3. Essential Terms hormone
chemical mediator that helps maintain homeostasis
target cell
cell with a receptor that responds to the presence of a hormone

4. General Characteristics
Glands that secrete chemical signals (hormones) into circulatory system
Hormone characteristics
Produced in small quantities
Secreted into intercellular space
Transported some distance in circulatory system
Acts on target tissues elsewhere in body
Regulate activities of body structures

5. Endocrine System Functions
Metabolism and tissue maturation
Ion regulation
Water balance
Immune system regulation
Heart rate and blood pressure regulation
Control of blood glucose and other nutrients
Control of reproductive functions
Uterine contractions and milk release

6. Endocrine Glands exocrine glands secrete products onto a surface
endocrine glands secrete products into the body fluids
hormones are carried to target tissues where activity is carried out
pituitary, thyroid, parathyroid, adrenal, pineal
Other hormone secreting structures
hypothalamus, thymus, pancreas, ovaries, testes, kidneys, stomach, liver, small intestine, skin, heart, adipose tissue, placenta

7. Figure 17.1

8. Regulation of Activities: Comparison of Endocrine and Nervous Systems
Endocrine: amplitude modulated signals.
Amount of hormone determines strength of signal
Onset within minutes of secretion of hormone
Nervous: frequency-modulated signals.
Frequency of action potentials produced by neurons determines strength of signal.
Onset within milliseconds
Two systems actually inseparable
Nervous system secretes neurohormones into circulatory system
Nervous system uses neurotransmitters and neuromodulators as ligands
Some parts of endocrine system innervated directly by nervous system

9. Intercellular Chemical Signals
Hormones: type of intercellular signal. Produced by cells of endocrine glands, enter circulatory system, and affect distant cells; e.g., estrogen
Autocrine: released by cells and have a local effect on same cell type from which chemical signals released; e.g., prostaglandin
Paracrine: released by cells and affect other cell types locally without being transported in blood; e.g., somatostatin
Pheromones: secreted into environment and modify behavior and physiology; e.g., sex pheromones
Neurohormone: produced by neurons and function like hormones; e.g., oxytocin
Neurotransmitter or neuromodulator: produced by neurons and secreted into extracellular spaces by presynaptic nerve terminals; travels short distances; influences postsynaptic cells; e.g., acetylcholine.

10. Functional Classification of Intercellular Chemical Signals

11. Functional Classification of Intercellular Chemical Signals

12. Control of Secretion Rate
Most hormones controlled by negative feedback systems
Most hormones are not secreted at constant rate, but their secretion is regulated by three different methods
The action of a substance other than a hormone on an endocrine gland.
Neural control of endocrine gland.
Control of secretory activity of one endocrine gland by hormone or neurohormone secreted by another endocrine gland

15. Table 17.1

16. Receptors hormones only affect target cells
water soluble hormone receptors on outside surface and trigger response inside the cell
lipid soluble hormone receptors on inside of cell and trigger response inside cell
target cells generally have between 2,000 and 100,000 receptors for a given hormone

17. Chemical Classes of Hormones
water soluble
amino acid based
lipid soluble
steroids
thyroid hormones
nitric oxide
transported in blood by transport proteins
slow rate of loss in kidneys
ready reserve of hormone in blood stream

18. Table 17.2 pt 1

19. Table 17.2 pt 2

20. Hormone Action variable depending on hormone and target cell
various targets respond differently to same hormone
some hormones activate synthetic or stimulatory processes
others activate degradation or inhibitory processes

21. Figure 17.2

22. Figure 17.3

23. Hormone Interactions permissive effects synergistic effects
one hormone allows the other to function
synergistic effects
one hormone intensifies the effects of the other
antagonistic effects
one hormone inhibits or reduces the effects of the other

24. Control of Hormone Secretion
hormones secreted in bursts
as stimulation increases bursts increase in frequency
in absence of stimulation, bursts are minimal or inhibited
regulated by
neural signals
chemical changes in blood
other hormones

25. Hypothalamus & Pituitary Gland

26. Hypothalamus controls the activity of the pituitary gland
major integrating link between the nervous and endocrine systems
hormones that stimulate anterior pituitary are all either releasing hormones or inhibiting hormones

27. Releasing and Inhibiting Hormones
Tropins or tropic hormones: hormones that regulate the hormone secretions of target endocrine tissues. All anterior pituitary hormones are tropins.
Releasing hormones:
GHRH. Growth hormone-releasing hormone. Causes the anterior pituitary to release growth hormone.
TRH. Thyroid-releasing hormone. Causes the anterior pituitary to release thyroid- stimulating hormone (TSH).
CRH. Corticotropin-releasing hormone. Causes anterior pituitary to produce adrenocorticotropic hormone.
GnRH. Gonadotropin-releasing hormone. Causes anterior pituitary to produce FSH (follicle stimulating hormone) and LH (luteinizing hormone).
PRH. Prolactin-releasing hormone. Causes the anterior pituitary to release prolactin.
Inhibiting hormones:
GHIH. Growth hormone-inhibiting hormone, somatostatin. Causes the anterior pituitary to decrease release of growth hormone.
PIH. Prolactin-inhibiting hormone. Causes the anterior pituitary to decrease release of prolactin.

28. Figure 17.4

29. Pituitary Gland two lobes anterior lobe posterior lobe
stimulated by tropic hormones from hypothalamus
hypophyseal portal system
posterior lobe
neural tissue that releases hormones produced in the hypothalamus
neurosecretory cells

30. Table 17.3

31. Figure 17.5

32. Figure 17.6

33. Figure 17.11

34. FSH & LH released by the anterior pituitary triggered by GnRH
target tissue gonads
FSH
in females initiates development of ovarian follicles
in males stimulates sperm production LH
in females triggers ovulation
in males triggers testosterone secretion

35. PRL released by the anterior pituitary
trigger is PRH and PIH from hypothalamus
initiates and maintains milk secretion and production by mammary glands in females
in males can cause erectile dysfunction

36. ACTH secreted by anterior pituitary triggered by CRH
also triggered by stress
controls production and secretion of hormones called glucocorticoids
cortisol from adrenal cortex
cause negative feedback regulation of CRH and ACTH release

37. Figure 17.16

38. MSH secreted by anterior pituitary function unknown in humans
presence of MSH receptors in brain suggests it may influence brain activity
excessive CRH stimulates MSH release
PIH inhibits MSH release

39. Table 17.4 pt 1

40. Table 17.4 pt 2

41. Posterior Pituitary

42. Posterior Pituitary AKA neurohypophysis
store and release two hormones produced by hypothalamus
ADH OT

43. Figure 17.4

44. OT
oxytocin
targets uterus and mammary glands during and after delivery
uterus contracts
milk ejection (“let down”)
function in non-reproducing women and in men is unknown
animal studies seem to indicate parental caretaking behavior toward offspring
sexual pleasure during and after intercourse

45. ADH antidiuretic hormone decreases urine production
kidneys return water to blood
decreases sweating
causes constriction of arterioles
increases blood pressure
AKA vasopressin

46. Figure 17.8

47. Table 17.5

48. Thyroid Gland

49. TSH follicular cells produce parafollicular cells produce
thyroxine (T4)
triiodothyronine (T3)
parafollicular cells produce
calcitonin
involved in calcium homeostasis
brings calcium levels down when too high

50. Figure 17.11

51. Actions of Thyroid Hormones
thyroxine and triiodothyronine
regulate oxygen use and BMR

52. Abnormal Thyroid Conditions

53. Parathyroid

54. PTH parathyroid hormone
major regulator of calcium, magnesium, and phosphate ions in blood
PTH brings blood levels of calcium up when too low

55. Figure 17.13

56. Table 17.7

57. Causes and Symptoms of Hypersecretion and Hyposecretion of Parathyroid Hormone

58. Adrenal Gland

59. Adrenal Cortex divided into three zones each secretes its own hormone
mineralocorticoids
glucocorticoids
androgens

60. Figure 17.15

61. Figure 17.16

62. Figure 17.5

63. Glucocorticoid Functions
Protein breakdown
Glucose formation
Triglyceride breakdown
Resistance to stress
Anti-inflammatory effects
Depression of immune responses

64. Adrenal Medulla modified sympathetic ganglion of ANS epinephrine
norepinephrine

65. Symptoms of Hypersecretion and Hyposecretion of Adrenal Cortex Hormones

66. Pancreas

67. Figure 17.17a

68. Figure 17.17b

69. Figure 17.17c

70. Figure 17.17d

71. Blood Glucose Level Regulation
glucagon released when
blood glucose is low
insulin released when
blood glucose is high

72. Figure 17.18

73. Table 17.9

74. Gonads

75. FSH & LH
estrogens
progesterone
testosterone
androgens

76. Table 17.10

77. Pineal Gland

78. Pineal Gland hormone secreted is melatonin
contributes to setting the body’s biological clock
promotes sleepiness in small doses
in animals with breeding seasons, melatonin inhibits reproductive functions outside the season