Adrenal Medulla & Cortex Flashcards
What does the adrenal cortex produce?
mineralocorticoids
glucocorticoids
androgens
What does the adrenal medulla produce?
epinephrine
norepinephrine
The adrenal medulla has ______ innervation, with preganglionic fibers originating in the ________
sympathetic (specialized sympathetic ganglion)
thoracic spinal cord
What cells secrete catecholamines? What do they produce?
chromaffin
Epi
NE
Epi acts on which alpha and beta receptors?
ALL
NE acts on which alpha and beta receptors?
alpha 1 & 2, beta-1
The predominant catecholamine is _____ at what %?
epinephrine
80%
What converts NE into Epi? Under what influence?
phenylethanolamine-N_methyltransferease (PNMT)
influence of cortisol
Cortisol is made in the _____
cortex
so it reaches medulla in high concentrations
Epi is stored in _______ and released when activated by [SNS/PSNS]
granules
SNS
ALL epi originates from the _____
adrenal medulla
Most NE originates from _____ & ______. Only a small amount from the adrenal medulla
sympathetic nerve terminals
brain
What are the target tissues of catecholamines?
muscle cells
liver
Most metabolism of catecholamines occurs in the ____ & _____
liver
kidneys
What regulates catecholamine secretion?
fight or flight responses (danger, pain, hypervolemia, hypotension, anorexia, etc)
What are the effects of catecholamines?
increased heart rate, cardiac output, blood pressure
redistribution of blood towards skeletal muscle
increased respiration (ventilation and dilation in airways)
increased blood glucose
During fight or flight activation, blood is shunted away from what systems? What metabolically happens?
GIT
reproduction
urinary
increase in lipolysis and maybe gluconeogenesis
What are the zones of the cortex?
zona glomerulosa
zona fasciculata
zona reticularis
What hormone is in the zona glomerulosa?
aldosterone
What hormone(s) is/are in the zona fasciculata?
cortisol - lots of mammals
corticosterone - rat, mouse, rabbit
What hormone(s) is/are produced in the zona reticularis?
androgen precursors
DHEA —> dehydroepiandosteroine
andostendoine
What is the precursor for all steroids?
cholesterol
Steroid hormone production is catalyzed by
cytochrome P450 systems in mitochondria and endoplasmic reticulum
Cholesterol comes from…
diet
MOST from circulation
some de novo synthesis
What enzyme converts cholesterol to pregnenolone?
cholesterol desmolase (using ACTH from anterior pituitary gland)
What is the rate-limiting step in steroid hormone production?
conversion of cholesterol to pregnenolone
- nothing is stored in the cell, so conversion via cholesterol desmolase is a critical step
All layers of the adrenal cortex contain what enzyme?
cholesterol desmolase
The direction of steroid hormone production pathway depends on presence/absence of ______ to catalyze modifications
enzymes
What enzymes are required to synthesize aldosterone in the zona glomerulosa?
aldosterone synthase
cholesterol desmolase
Which enzyme is under the influence of angiotensin II?
aldosterone synthase
What are the functions of aldosterone?
long-term regulation of blood pressure
exhibits diurnal pattern
The primary regulation for aldosterone occurs via changes in ________
ECF volume via RAAS pathway
changes in blood potassium
Aldosterone is transported in the BLOOD by
aldosterone-binding globulin
transcortin
albumin
A decrease in ECF leads to a decrease in …? Then leads to an increase in?
renal blood perfusion
renin secretion by kidney
What also stimulates aldosterone secretion?
increase in blood K+ concentration
- depolarizes adrenal cells to open CA2+ changes to stimulate aldosterone
The first step towards cortisol (after converted to pregnenolone) is what enzyme?
17alpha-hydroxylase
What is the final enzyme in the cortisol pathway? What does it convert?
11beta-hydroxylase
converts 11-deoxycortisol to cortisol
Cortisol is regulated by what?
hypothalamic-pituitary adrenal axis
CRH - hypothalamus
ACTH - ant pituitary
How is cortisol transported in blood?
transcortin
Cortisol is metabolized where and how?
liver
excreted in urine using glucuronides
List factors that stimulate ACTH secretion
stress - hypoglycemia, infections, fever (physiological)
low cortisol
ADH
List factors that inhibit ACTH secretion
high cortisol
exogenous steroids
somatostatin
dopamine (tonic inhibition at the pars intermedia in horses)
Once cortisol is released, it provides ____ to [inhibit/stimulate] ACTH release. It [quickens/slows] ACTH synthesis, which takes _____
long-loop feedback - minutes
inhibit
slows feedback
hours
Cortisol also has a ______ to [stimulate/block] CRH release
long-loop feedback
block
Once ACTH is released, it provides ____ to [inhibit/stimulate] CRH release.
short-loop feedback
inhibits
What is the mechanism of action of cortisol at the tissue level?
cortisol binds type II glucocorticoid receptor in cytosol
receptor-hormone complex moves into nucleus and binds another receptor on DNA
active gene transcription and translation
The half-life of aldosterone is ____, and the half-life for cortisol is ______
20 min
60-90 min
Aldosterone exhibits a ____ pattern. What does this mean?
diurnal
lowest levels of hormone around midnight and highest at awakening
Cortisol exhibits a _____ pattern. What does this mean?
pulsatile / episodic
Wille keep ~2 hrs before awakening
