Hypothalamic-Adenohypophyseal-Adrenocortical Axis I: CRH & ACTH

Created by Evie35 

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28 terms · Relevant to veterinary medicine

hormones of the Hypothalamic-Adenohypophyseal-Adrenocortical Axis

CRH (corticotropin releasing hormone), ACTH (adrenocorticotropic hormone), steroid hormones (corticosteroids)

CRH is secreted by this part of the brain

hypothalamus

ACTH is secreted by this part of the brain

adenohypophysis/anterior pituitary

ACTH secretion is stimulated by this

CRH

CRH secretion is stimulated by this

stressful physical, chemical, and emotional stimuli such as trauma, exercise, hemorrhage, pain, hypoglycemia, LPS, overcrowding, extreme temps.

ACTH secretion is inhibited by this

cortisol

steroid hormones are secreted by this part of the brain

adrenal cortex

the steroid hormones produced in the brain

aldosterone, cortisol, estradiol

aldosterone is produced in this part of the adrenal cortex

zona glomerulosa

cortisol is produced in this part of the adrenal cortex

zona fasiculata

estradiol (sex steroids) is produced in this part of the adrenal cortex

zona reticularis

cortisol inhibits the production of these hormones by negative feedback inhibition

CRH & ACTH

this causes too little production of ACTH

diminished blood flow to adenohypophysis

this causes too much production of ACTH

destruction of adrenal cortex (less cortisol to perform negative feedback inhibition)

ACTH promotes the uptake of this substance in all three zonae of the adrenal cortex so they can enzymatically convert it into aldosterone, cortisol, and estradiol

cholesterol

ACTH promotes mitosis/growth, overall health and integrity, but does not directly stimulate the pathway to make this

aldosterone

these substances do not influence the production of CRH or ACTH, only cortisol does

aldosterone & estradiol

Cushing's disease is an adenoma in the pituitary of these cells

corticotrophs

in Cushing's, the adenohyphysis is not listening to cortisol negative inhibition feedback, so it keeps making this

ACTH

in Cushing's, overproduction of ACTH causes this to happen

adrenal cortex overproduces cortisol which exerts excessive negative feedback inhibition on the hypothalamus to reduce production of CRH

in Cushing's, even though the hypothalamus's production of CRH is inhibited, ACTH is still being made because of this

only a small amount of CRH is needed to stimulate the adenohypophysis to make ACTH

in Addison's disease, an animal can't make adequate amounts of this

cortisol

ACTH is not bound by these

plasma proteins

ACTH causes increased glucose entry, glycogenolysis, and glycolysis at these zonae

fasciculata and reticularis

ACTH turns on enzymes but needs these 2nd messengers because it's stuck at the membrane

cAMP and PKA

ACTH is not actually needed at this zona because increased K+ and angiotensin II stimulate its pathway

glomerulosa

essential enzyme in glucocorticoid pathway to produce cortisol

17-OH (17-hydroxylase)

ACTH is degraded by these

cytoplasmic enzymes

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