Adrenal gland and HPA Flashcards
The adrenal medulla is innervated by what
sympathetic preganglionic efferent nerves
True/False: adrenal medullary cells function as post ganglionic sympathetic “neurons”
true
What are the three zones of the adrenal cortex and what do they produce
Zona glomerulosa: mineralcorticoids
Zona fasiculata: glucocorticoids
Zona reticularis: androgens
The precursor for all adrenocortical steroids is ___
cholesterol
What is the main product of the adrenal medulla
catecholamines
What is the rate limiting step/essential enzyme in the synthesis of adrenocortical steroids?
cholesterol desmolase stimulated by ACTH
Cholesterol uptake by the adrenal cortex is regulated by ____
ACTH
True/False: cholesterol is stored inside adrenal cortex cells until it is required fro hormone synthesis
true
True/False: adrenocortical steroids are stored in secretory vesicles until they are needed
false!! they are synthesized as needed
what is the common precursor for all adrenocortical hormones?
pregnenolone
The specialization of the zones of the adrenal cortex is conferred by _____
the enzymes present
Mineralocorticoid secretion is controlled by what?
RAAS
Glucocorticoid and androgen secretion are controlled by what?
HPA which is under classical negative feedback control
What is the main method of action of steroid hormones?
they bind to intracellular receptors and act through transcription of DNA and synthesis of new proteins
What is the physiologically most important mineralocorticoid?
aldostrone
Aldostrone secretion is regulated by what?
extracellular fluid volume
changes in serum K+ levels
True/False: ACTH is required fro aldostrone synthesis, but is of minor importance in the secretion rate
true
True/False: K+ changes act indirectly on aldostrone producing cells
false, it DIRECTLY acts on aldostrone producing cells
What are the immediate and slow onset effects of aldostrone
Immediate effect: prolongs the opening of Na+ channels in the apical membrane of the renal distal tubules and collecting ducts
Slow onset effect: increases synthesis of Na+ and K+ channels in the apical membrane and Na+/K+ pump in the basolateral membrane of the renal tubular epithelium
How is aldostrone excreted?
it is conjugated in the liver and excreted in the urine and bile
What is the overall effect of glucocorticoids in glucose metabolism
increases blood glucose concentration
True/False: glucocorticoids have a prominent circadian variation
true
True/False: nothing (besides drugs) can override the circadian rhythm of glucocorticoid secretion
false, stress can override this rhythm
True/False: all nucleated cells have glucocorticoid receptors
true
True/False: glucocorticoids increase gluconeogenesis, proteolysis, and lipolysis
true
What is the effect of glucocorticoids on insulin sensitivity
they decrease it
What is the overall effect of glucocorticoids on inflammatory and immune responses
they have a general inhibiting effect
Glucocorticoids are rapidly released in response to what 4 major types of stress
trauma
infection
environmental temperature variations
psychological stress
You run pre op bloodwork on a 3yo cat and find everything WNL except the glucose, which is slightly elevated. Is this normal? why /why not
it can be normal due to stress. The psychological stress can cause the secretion of glucocorticoids which has a general effect of increasing blood glucose concentration
Glucocorticoids will mobilize protein from all tissues except ____ for use in proteolysis
liver
How do glucocorticoids have broadly immunosuppressive effects?
cortisol induces synthesis of lipocortin which inhibits phospholipase A2 which is responsible for prostaglandin and leukotriene production
What 4 hormones/molecules require the presence of cortisol to be affective
insulin, glucagon, GH, and angiotensin II
What are catecholamines synthesized from?
tyrosine
what catecholamine is secreted in higher quantities
epinephrine
Where are catecholamines inactivated
the liver and kidneys
What are three important physiologic effects of catecholamines
-elevated plasma glucose
-mobilization of fatty acids as a source of energy
-redistribution of blood supply to preserve blood flow to heart and brain
