adrenal Flashcards
what type of neurons innervate the adrenal glands?
sympathetic postganglionic neurons
will the adrenal medulla regenerate?
no
will the adrenal cortex regenerate?
yes
where is the zona arcuata (aka glomerulosa) located?
superficial adrenal cortex
where is the zona fasciculata + reticularis located?
deep in the adrenal cortex
where is the site of mineralocorticoid synthesis?
zona arcuata
where is the site of glucocorticoid and sex hormone synthesis?
zona fasciculata + reticularis
is the zona arcuata responsive to ACTH?
no
is the zona fasciculata + reticularis responsive to ACTH?
yes
loss of ACTH does what to the adrenal cortex?
produces a thin adrenal cortex
T/F: the thickness of the zona glomerulosa is affected by loss of ACTH.
false
what is the non-specific response to injury or stress by the adrenal glad?
general adaption syndrome
adrenocortical hormones are derivatives of what?
cholesterol
what are the two sources of cholesterol?
- synthesis in the adrenal cortex
- plasma LDL cholesterol
- (liver)
in the steroid nucleus of adrenocortical hormones, how many carbons are there?
C-21s
what enzyme does trilostane block?
3,b-dehydrogenase
the synthetic pathway of adrenocortical hormone involves what 2 organelles?
- smooth endoplasmic reticulum
- mitochondria
do mineralocorticoids have a C17 hydroxyl group?
no
do glucocorticoids have a C17 hydroxyl group?
yes
where are binding proteins synthesized
the liver
what does total glucocorticoid in blood depend on?
- secretion rate
- metabolism
- amount of carrier protein
how do steroid travel in aqueous solution (blood)?
binding protein carry the steroid
what are steroid binding proteins?
- transcortin for cortisol
- albumin
- free hormone (no protein)
what is the reltaionshipt of [cortisol] to [aldosterone]?
[cortisol] is more than 10 fold higher than [adosterone]
what is the clearance of cortisol?
60 min half life
what is the clearance of aldosterone
20 min half life
what causes the differences in the half lives of cortisol and aldosterone?
the carrier protein
how/where are steroid hormones metabolized?
- reduction in the liver
- hormones rendered water soluble
- excreted in urine
what is the importance of mineralcorticoids?
they are acutely critical for maintaining life
what is the most important mineralcorticoid?
aldosterone
what does aldosterone protect against?
- hypotension
- hyopnatremia
- potassium intoxication
to prevent overstimulation of aldosterone receptor by cortisol, ______ converts ______ to inactive _____.
- 11-b hydroxysteroid dehydrogenase
- cortisol
- cortisone
can cortisone bind to the mineralcorticoid receptor?
no
licorice can inhibit what?
leading to what?
- 11-b hydroxysteroid dehydrogenase
- mineralcorticoid excess syndrome
what are the physiological actions of aldosterone?
- increases na+ reabsorption from urine, saliva and gastric juices
- increases angiontensin II production
- decreases K+ by increasing renal excretion
- conservation of water follows the conservation of na+
what behavior does aldosterone cause together with angiontensin II?
drives salt seeking behavior
what regulates aldosterone?
-plasma K+ will stimulate aldosterone by a DIRECT EFFECT ON adrenal zona glomerulosa
-angiotensin II
-poorly regulated ACTH
suppressed by atrial natriuretic factor
-high plasma Na+ and K+ deficiency decrease aldosterone secretion
aldosterone and angiotensin II act upon what?
distal tubule and collecting duct
what happens when aldosterone and angiotensin II are acting on the kidney?
- resorption of renal sodium and water
- excretion of potassium
where is renal renin released?
from the juxtaglomerular apparatus (JG)
do aldosterone and angiotensin II synergize?
yes
the JG complex acts as what?
a baroreceptor
what is the most important glucocorticoid in most species?
cortisol
what is the most important glucocorticoid in rabbits, mice and rats?
corticosterone
what is the main physiological effect of cortisol?
to stimulate gluconeogenesis -> amino acids to glucose, glycogen to glucose
cortisol acts on ____ to release ____.
- liver
- gluconeogenic enzymes
what are the 7 effects of cortisol?
- stimulate gluconeogenesis
- stimulate protein and fat catabolism
- redistribution of body fat
- water and electrolyte distribution
- trace mineral distribution
- blocks inflammatory responses
- suppresses immune system
what is the most clinically important effect of cortisol?
that it blocks inflammatory responses
how is cortisol regulated?
by negative feedback
what is the most important hormone of the pars intermedia?
alpha-MSH
what is the most potent glucocorticoid?
cortisol
what are three ways you can test adrenocortical function?
- plasma [cortisol]
- ACTH response test
- dexamethasone suppression test
what are 4 clinical uses of glucocorticoid?
- inhibition of inflammatory response
- immunosuppressant
- palliative therapy for arthritis, arthrosis
- replacement therapy for hypoadrenocorticism
what animals are most prone to hypoadrenocorticism?
older, female, small breed dogs
what is the common term for hyperadrenocorticism?
Cushing’s-like syndrome
what causes cushing’s disease?
secondary to pituitary release of excess ACTH
-pituitary dependent
what causes cushing’s syndrome?
primary hyperadrenocorticism due to adrenal tumor
-adrenal dependent
what is cushings sydrome?
- excessive glucocorticoid synthesis
- secondary to excessive ACTH
what is the common name for hyperaldosteronism?
conn’s syndrome
primary conn’s syndrome is caused by what?
adrenal tumor
adenoma
secondary conn’s syndrome is caused by what?
renovascular disease leading to ang II increase
what is PPID in horses?
- equine cushing’s
- pituitary pars intermedia dysfunction
what is a key sign of hypoadrenocorticism?
- bradycardia/widened QRS complex
what causes hypoadrenocorticism?
deficiency of mineralocorticoids (aldosterone)
cells of the adrenal medulla are innervated by what type of nerve fibers?
pre-ganglionic sympathetic nerve fibers
cells of the adrenal medulla are modified by what type of nerve fibers?
post-ganglionic nerve fibers
what are the primary hormones synthesized by the adrenal medulla?
epinephrine and norepinephrine
what is the key precursor for catecholamine synthesis?
tyrosine
tyrosine is inhibited by what?
NE and EPI
the actions of catecholamines are mediated by?
alpha- and beta-adrenergic receptors
the actions of catecholamines by alpha-receptors are?
- vasoconstriction by NE
- liver glycogenolysis
the actions of catecholamines by beta-receptors are?
- increased heart rate/contractility
- bronchodilator
- adipose tissue lipolysis
- vasodilation by epinephrine
sympathetic tone is regulated by what?
baroreceptors
what is pheochromocytoma?
- means dusky tumor
- neoplasm (often adenoma) in adrenal medulla
- can release catecholamines
