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Physiology > Adrenal Medulla and Cortex > Flashcards

Adrenal Medulla and Cortex Flashcards

1
Q

Adrenal glands are located where?

A

in the retroperitoneal cavity above each kidney

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2
Q

The adrenal cortex produces what?

A
  • mineralcorticoids
  • glucocorticoids
  • androgens
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3
Q

The adrenal medulla produces what?

A
  • epinephrine
  • norepinephrine
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4
Q

Where is the adrenal medulla located?

A

in the inner zone of the gland and surrounded by the cortex

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5
Q

Chromaffin cells of the adrenal medulla secrete what?

A

catecholamines (epi and NE)

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6
Q

Epi acts on which adrenergic receptors?

A

all alpha and beta adrenergic receptors

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7
Q

NE acts on which adrenergic receptors?

A

alpha 1 and 2, beta 1

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8
Q

How is the adrenal medulla considered a specialized sympathetic ganglion?

A

receives input from sympathetic nervous system via preganglionic fibers originating in the thoracic spinal cord

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9
Q

What is the predominant catecholamine synthesized?

A

epinephrine

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10
Q

Epi is stored in granules and released when activated by what?

A

SNS

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11
Q

What enzyme converts NE to Epi under the influence of cortisol?

A

phenylethanolamine-N-methyltransferase (PNMT)

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12
Q

All Epi originates from where?

A

adrenal medulla

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13
Q

Most NE originates from where?

A

sympathetic nerve terminals and brain

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14
Q

What are the target tissues of catecholamines?

A
  • muscle cells
  • liver
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15
Q

Most metabolism of catecholamines occurs where?

A
  • liver
  • kidneys
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16
Q

What are the effects of catecholamines?

A
  • increased HR, cardiac output, BP
  • redistribution of blood toward skeletal muscle
  • increased respiration
  • increased blood glucose
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17
Q

What are the zones of the adrenal cortex?

A
  • zona glomerulosa
  • zona fasciculata
  • zona reticularis
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18
Q

What is the major hormone secreted by the zona glomerulosa?

A

aldosterone

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19
Q

What are the major hormones secreted by the zona fasciculata?

A
  • cortisol in humans, dogs, cats, sheep, cows, pigs, horses
  • cortisterone in rats, mice, rabbits
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20
Q

What are the major hormones secreted by the zona reticularis?

A

androgen precursors (dehydroepiandrosterone and androstendione)

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21
Q

What is the precursor for all steroids?

A

cholesterol

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22
Q

What is the rate limiting step of steroid hormone production?

A

conversion of cholesterol to pregnenolone (first step)

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23
Q

Steroid hormone production is catalyzed by what system in mitochondria and endoplasmic reticulum?

A

cytochrome P450

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24
Q

All layers of the adrenal cortex have what enzyme?

A

cholesterol desmolase

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25
Q

The direction of steroid hormone production pathway depends on what?

A

presence/absence of enzymes to catalyze modifications

26
Q

What is the site of production for mineralcorticoids (aldosterone)?

A

zona glomerulosa

27
Q

The production of mineralcorticoids requires what?

A
  • ACTH to stimulate cholesterol desmolase
  • aldosterone synthase
28
Q

Primary regulation of aldosterone occurs via what?

A
  • changes in ECF volume via RAAS
  • changes in blood potassium
29
Q

Describe regulation of aldosterone secretion by RAAS.

A
  • mediator is angiotensin II
    1. decrease in ECF volume
    2. decrease in renal blood perfusion pressure
    3. increases renin secretion by kidney
  • ultimately, aldosterone stimulates Na reabsorption by kidney to restore ECF volume
30
Q

Describe regulation of aldosterone secretion by increases in blood K+ concentration.

A

depolarizes adrenal cells to open Ca channels to stimulate aldosterone secretion –> increase K+ excretion in kidneys

31
Q

What is the site of production for glucocorticoids (cortisol)?

A

Zona fasciculata

32
Q

What is the first step in producing glucocorticoids?

A

catalyzation by 17 alpha-hydroxylase

33
Q

What is the purpose of the final enzyme (11 beta-hydroxylase) in glucocorticoid production?

A

converts 11-deoxycortisol to cortisol

34
Q

The production of glucocorticoids requires ACTH to do what?

A

stimulate cholesterol desmolase

35
Q

Cortisol is regulated by what?

A

hypothalamic-pituitary-adrenal axis

36
Q

Cortisol is transported in blood by what?

A

transcortin

37
Q

Cortisol is metabolized by ____, and excreted in urine using _____ (kidney).

A

liver, glucuronides

38
Q

What are the stimulators of ACTH secretion?

A
  • stress (hypoglycemia, infections/fevers)
  • low cortisol
  • ADH
39
Q

What are the inhibitors of ACTH secretion?

A
  • high cortisol
  • exogenous steroids
  • somatostatin
  • dopamine
40
Q

Does cortisol have long or short loop feedback to inhibit ACTH release?

A

long loop feedback

41
Q

What type of feedback does cortisol have to inhibit ACTH synthesis?

A

slow feedback

42
Q

Does cortisol have long or short loop feedback to block CRH release from hypothalamus?

A

long loop feed back

43
Q

What type of feedback does ACTH have to inhibit CRH release?

A

short loop feedback

44
Q

What is the mechanism of action of cortisol at tissue level?

A
  • cortisol binds type II glucocorticoid receptor in cytosol
  • receptor hormone complex moves into nucleus and binds another receptor on DNA (DNA response element)
  • activate gene transcription and translation
45
Q

Why are the effects of cortisol described as “permissive”?

A
  • does not directly initiate actions but allows critical processes to occue
  • amplifies actions of other hormones
46
Q

Which type of cortisol is biologically active?

A

only free cortisol

47
Q

Are the net effects of cortisol anabolic or catabolic?

A

catabolic

48
Q

What are the effects of cortisol on energy metabolism?

A
  • increases blood glucose
  • increases glycogenesis
  • increases lipolysis and protein catabolism
  • increases appetite, visceral obesity
49
Q

What are the effects of cortisol on musculoskeletal system?

A
  • increases protein catabolism
  • inhibits bone formation
  • increases bone resorption
  • causes osteoporosis
  • inhibits collagen synthesis
  • causes thin skin and fragile capillaries
50
Q

What are the effects of cortisol on kidneys and cardiovascular system?

A
  • increases glomerular filtration rate in kidney and decreases ADH for water balance
  • helps maintain normal blood pressure and volume
  • up regulates alpha 1 adrenergic receptors which is necessary for vasoconstrictive response of arterioles to NE and Epi
51
Q

What are the effects of cortisol on the immune system?

A
  • suppresses immune system by suppressing prostaglandins, thromboxanes, leukotrienes
  • decreases neutrophil activity, formation of cytokines, T-lymphocytes, and antibody formation
  • specific anti-inflammatory effects including: induces lipocortin, inhibits production of interleukin-2, and inhibits release of histamine
52
Q

What is the innermost cortical layer?

A

zona reticularis

53
Q

The zona reticularis produces what?

A

weak androgens: DHEA, DHEA sulfate, androstenedione

54
Q

What enzyme is needed for the androgen pathway?

A

17, 20-lyase

55
Q

What are some adrenal cortex dysfunctions?

A
  • cushings syndrome (hyperadrenocorticism)
  • addision’s disease (hypoadrenocorticisim)
  • hyperaldosteronism
  • alopecia X (atypical hyperadrenocorticism)
56
Q

What are causes of cushings syndrome (hyperadrenocorticism)?

A
  • pituitary dependent hyperadrenocorticism (PDH) with bilalteral adrenal hyperplasia
  • pars intermedia dysfunction
  • adrenal tumors
  • iatrogenic hyperadrenocorticism resulting from chronic excessive exogenous steroid administration
57
Q

What are causes of addisons disease (hypoadrenocorticism)?

A
  • autoimmune
  • infiltrative disease (cancers)
  • idiopathic
  • iatrogenic steroids
58
Q

Addisions disease results in losses of what?

A
  • aldosterone
  • cortisol
59
Q

Alopecia X is characterized by what?

A

elevation in androgens and/or sex hormones

60
Q

What are causes of primary hyperaldosteronism?

A
  • idiopathic adrenal hyperplasia (bilateral)
  • tumor (unilateral or bilateral)
61
Q

What are causes of secondary hyperaldosteronism?

A
  • liver disease
  • kidney disease (activating RAAS)

Physiology (18 decks)

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