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Physiology > Adrenal Physiology > Flashcards

Adrenal Physiology Flashcards

1
Q

The adrenal cortex is involved in ______ hormone synthesis

A

Steroid

  • cortisol: gluconeogenesis, anti-inflammatory (regulated by HPA axis)
  • aldosterone: blood volume regulation, secretion of K and resorption of Na from kidney (regulated by RAAS)
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2
Q

Adrenal medulla is responsible for synthesizing ________

A

Catecholamines

- regulation via SNS

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3
Q

The zona fasiculata produces _____

A
  • cortisol

- corticosterone

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4
Q

The zona glomerulosa produces _______

A

Aldosterone

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5
Q

The zona reticularis produces ________

A

Androstenedione

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6
Q

Corticosteroids

A

Refers to all hormones made in the adrenal glands

  • glucocorticoids (cortisol)
  • mineralcorticoids (aldosterone)
  • sex steroids (progestogens, androgens, estrogens)
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7
Q

Anabolic steroids

A
  • increased protein synthesis
  • increased muscle mass
  • typically androgens
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8
Q

Catabolic steroids

A
  • decreased protein synthesis
  • decreased muscle mass
  • usually glucocorticoids: cortisol, prednisone
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9
Q

Adrenal gland components

A
  • adrenal cortex (80%) –> steroid hormones

- adrenal medulla (20%) –> catecholamine synthesis, SNS regulation

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10
Q

Catecholamine synthesis

A
  • released into blood
  • fight or flight
  • norepinephrine (cat)
  • epinephrine (dog, human)
  • increase metabolic rate
  • increase blood pressure, cardiac contractility, myocardial excitablity
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11
Q

Pheochromocytoma

A

Tumor of adrenal medulla with excess production of catecholamines

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12
Q

Cortex components

A
  • glomerulosa (15%)
  • fasiculata (75%)
  • reticularis (10%)
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13
Q

Glomerulosa

A
  • specific enzyme: aldosterone synthase

- product: mineralocorticoids

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14
Q

Fasiculata

A
  • specific enzyme: 17alpha-hydroxylase

- product: glucocorticoids, sex hormones

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15
Q

Reticularis

A
  • specific enzyme: 17alpha- hydroxylase

- products: glucocorticoids, sex hormones

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16
Q

Steroids are degraded in the ______

A

Liver

  • free hormone
  • conjugated to glucuronide
  • excreted thru urine, bile
  • inhibited if diseased
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17
Q

Steroids are bound to proteins 94%, but only the ________ is active

A

Free hormone

18
Q

Cortisol metabolism

A
  • corticosteroid-binding globulin (CBG)
  • albumin
  • T1/2 < 2 hrs
19
Q

Aldosterone metabolism

A
  • albumin
  • slightly bound
  • T1/2 is 20 minutes
20
Q

Steroidal mechanism of action

A

Free hormone diffuses into cell (lipophilic) –> binds cytoplasmic receptor –> translocates to nucleus, binds DNA –> directs transcription (proteins)

21
Q

What are the cellular functions of cortisol?

A
  • catabolic: gluconeogenesis, anti-insulin, protein
  • anti-inflammatory
  • anti-stress
  • receptors in most cells*
22
Q

Catabolic effects of cortisol on carbohydrates

A
  • stimulates hepatic gluconeogenesis
  • inhibits effects of insulin
  • fight or flight
  • protects from hypoglycemia
23
Q

Catabolic effects of cortisol on lipids

A
  • mobilizes fatty acids

- redistribution

24
Q

Catabolic effects of cortisol on proteins

A
  • inhibits cellular uptake of amino acids
  • stimulates gluconeogenesis
  • muscle breakdown
  • skin, CT, bone
25
Q

Anti-inflammatory/immunosuppressive function of cortisol

A
  • stabilization of lysosomes
  • decreases: capillary permeability, margination of WBCs
  • suppression of T lymphocytes
  • decreases fever (IL-1)
  • blocks allergies
  • give glucocorticoids during anaphylactic shock*
26
Q

3 functions of cortisol

A
  • resistance to stress
  • stimulation of erythropoiesis
  • maintenance of vascular tone
27
Q

Functions of cortisol: summary

A
  • gluconeogenesis
  • protein catabolism
  • stress resistance
  • anti inflammatory
  • immunosuppressive
28
Q

The hypothalamic-pituitary-adrenal axis

A 
Hypothalamus
- corticotropin releasing hormone
- physical, emotional, chemical stress
Anterior pituitary
- adrenocorticotropic hormone
Adrenal gland
- cortisol
29
Q

Adrenocorticotropic hormone

A 
Episodic secretion (concentration varies)
- precursor: pro-opiomelanocortin (POMC)
30
Q

ACTH mechanism of action

A

Increase free cholesterol –> conversion of cholesterol to pregnenolone –> major action of ACTH –> rate-limiting step in cortisol synthesis
- trophic effect

31
Q

Increase stress in a normal dog results in:

A

Hypothalamus increases CRH –> pituitary increases ACTH –> adrenal increases cortisol

32
Q

Feedback inhibition

A
  • increased ACTH = decreased CRH
  • increased cortisol = decrease CRH
  • increased cortisol = decreased ACTH
33
Q

Would you measure cortisol to determine if a dog has hypoadrenocorticism?

A

No, ACTH is secreted episodically so a normal dog could have a low cortisol

34
Q

What happens if you give dexamethasone to a healthy dog?

A

Dex will suppress cortisol production, so the cortisol levels will be less than the level collected before the injection

35
Q

Pituitary tumor

A

Will cause:

  • increased ACTH
  • bilaterally increase adrenals
  • increase cortisol
36
Q

________ is the most important endogenous mineralocorticoid

A

Aldosterone

  • 90% of body’s mineralocorticoid effects
  • some glucocorticoids have a small amount of mineralocorticoid effect
37
Q

Aldosterone release is stimulated by

A
  • decreased blood volume, decreased sodium

- increased potassium

38
Q

Primary functions of aldosterone

A
  • increased Na, Cl and water resorption

- increased K and H excretion

39
Q

Aldosterone site of action

A

Principal cells of distal tubules and collecting ducts

  • increase activity of basolateral Na/K ATPase
  • increase transcription of luminal Na channels
40
Q

Renin-angiotensin-aldosterone system (RAAS)

A 
Renin
- released from afferent arteriole
- response to hypovolemia
Angiotensin
- renin converts angiotensingogen to AT
- AT converted to AT2 by ACE in the lungs
- AT2 stimulates aldosterone synthesis
41
Q

Aldosterone regulation

A

Hypovolemia –> increase renin –> stimulates conversion of angiotensinogen to angiotensin –> AG2 by angtiotensin converting enzyme –> AT2 stimulates production of aldosterone

Physiology (33 decks)

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