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Physiology > Pituitary Hormones and Their Control by the Hypothalamus > Flashcards

Pituitary Hormones and Their Control by the Hypothalamus Flashcards

1
Q

Which hormones are released by the posterior pituitary gland?

A
  1. ADH
  2. oxytocin
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2
Q

Which hormone are released by the anterior pituitary gland?

A
  1. prolactin
  2. GH
  3. TSH
  4. FSH
  5. LH
  6. ACTH
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3
Q

Where are the posterior pituitary hormones synthesized?

A

In the magnocellular neurons located in the hypothalamus

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4
Q

How are ADH and oxytocin released?

A
  • made in the hypothalamus
  • packed in secretory granules with another protein (carrier protein, neurophysin) as preprohormone
  • travels down the axon in the pituitary stalk
  • stored at nerve terminal at the posterior pituitary
  • released into the capillary plexus on the inferior hypophysial artery
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5
Q

What are the 5 cell types that produce hormone of the anterior pituitary?

A
  1. Somatotropes –> growth hormone
  2. Thyrotropes –> thyroid stimulating hormone (thyrotropin)
  3. Corticotropes –> adrenocortical tropic hormone
  4. gonadotropes –> follicle stimulating hormone & luteinizing hormone
  5. Lactotropes –> prolactin
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6
Q

How is the blood supplied to the anterior pituitary?

A

-blood vessels enter the lowest portion of the hypothalamus @ the median eminence
- goes downward along the pituitary stalk
- then go through the hypothalamic-hypophysial portal vessels
- lastly, it makes it to the anterior pituitary sinuses

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7
Q

How does the hypothalamus control anterior pituitary secretion?

A

There is releasing/ inhibitory hormones synthesized and secreted by the hypothalamus
- these hormones are released by the nerve fibers to the median eminence & tuber cinereum into tissue fluids
- absorbed by the hypothalamus-hypophysial portal system
- carried directly to the anterior pituitary sinuses

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8
Q

What are the two inhibitory hormones produced by the hypothalamus?

A
  1. growth hormone inhibitory hormone (somatostatin)
  2. prolactin
    inhibitory hormone, aka, dopamine
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9
Q

Is hypothalamus the only place to control anterior pituitary hormone release?

A

No, metabolic substrates in the blood can also exert direct effect on the adenohypophysial cells

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10
Q

What are the 4 physiological functions of growth hormone?

A
  1. promotion of linear growth
  2. promotion of tissue protein deposition
  3. promotion of fat utilization for energy
  4. Impairment of carbohydrate utilization for energy
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11
Q

How is growth hormone diabetogenic?

A

It impairs carbohydrate update by tissues (uses fat as energy) so blood glucose level rises, and insulin secretion increases to compensate for the GH-induced insulin resistance

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12
Q

How doe growth hormone exert anabolic effects?

A
  • uses insulin-like growth factors (somatomedin)
  • IGF is secreted by liver and other tissues
  • both distant and local effects (paracrine/ autocrine)
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13
Q

How does growth hormone effect carbohydrate utilization?

A
  1. decrease glucose uptake by tissues such as the skeletal muscle and fat
  2. increase production of glucose by liver
  3. increase insulin secretion
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14
Q

How is the release of growth hormone controlled?

A

IGF-1 –> acts on the pituitary directly, or through action on hypothalamus (releases somatostatin)

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15
Q

What are some stimuli for growth hormone secretion?

A
  1. starvation
  2. hypoglycemia or low fatty acids in the blood
  3. exercise
  4. trauma
  5. excitement
  6. Ghrelin
  7. some amino acids, like arginine

hypoglycemia = potent

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16
Q

How does vasopressin work?

A

-acts on the epithelial cells of the collecting duct
- ADH/ V2 receptor –> activation of adenylcyclase –> formation of cAMP
- hypophosphorylation –> vesicle to insert the aquaporin into the apical cell membrane
- water is reabsorbed from the collecting tubules and ducts

17
Q

How is ADH release stimulated?

A
  • increase in osmolality
  • hypovolemia
  • hypotension
  • pain
  • stress
  • drugs
18
Q

How is ADH secretion regulated?

A

by osmoreceptors
- they are located outside of the BBB, in the circumventricular organs
- these receptors also mediate thirst response with increase osmolality

19
Q

How does vasopressin help in hypovolemia/ hypotension?

A
  • stretch receptors in atria will signal for increase/decrease vasopressin
  • constricts the vascular smooth muscle (V1 receptors)
  • mediated by Ca2+ and phospholipase C generated 2nd messengers
20
Q

What are the physiologic functions of oxytocin?

A
  1. Parturition
    - uterine smooth muscle contraction
    - stimulated by fetus head on cervix
    - response is enhanced by estrogen
  2. Milk let-down
    - contraction of the myoepithelial cells of the alveoli in the mammary gland
    - forces milk from the alveoli into the ducts
    - stimulated by sulking –> milk ejection reflex

Physiology (28 decks)

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