Adrenal Gland Flashcards
name the 3 zones of the adrenal cortex, the hormones secreted and what they are regulated by
- z. glomerulosa
- secretes aldosterone
- regulated by AG II
- z. fasiculata
- secretes mainly cortisol + some androgens
- regulated by ACTH
- z. reticularis
- secretes mainly androgens
- regulated by ACTH
what does the medulla secrete and what regulates it
- medulla
- secretes: epi + norepi
- regulated by sympathetic control
describe CRH
- released by PVN cells in the hypothalamus
- stimulates ACTH synthesis and release from AP
describe CRH signalling pathway
cAMP
what is ACTH derived from?
POMC
ACTH contains _____ in its sequence
- alpha-MSH is contained in the sequence of ACTH
- excess ACTH secretion results in hyperpigmentation
the precursor for all steroid hormones is _____
most of the cholesterol for synthesis comes from _____
adrenocortical cells have ____ which promotes ___ entry into cells
they are stored as _____ in the cell
the precursor for all steroid hormones is cholesterol
most of the cholesterol for synthesis comes from circulating cholesterol in LDL
adrenocortical cells have lipoprotein receptors which promotes cholesterol entry into cells
they are stored as lipid droplets in the cell
describe the MoA of ACTH
- ACTH binds to receptor and causes increase in cAMP
- StAR (steroidogenic active regulatory protein) becomes activated and promotes entry of cholesterol into mitochondria, where cholesterol is turned into pregnenolone
- also promotes steroidogenic enzymes DNA transcrption
name the short term and long term effects of ACTH
- short term
- increases conversion of cholesterol into pregnenolone
- long term
- increases number of LDL receptors
- increases transcription of synthesis enzymes which requires chronic exposure to ACTH
- clinical application: patients on long term corticosteroid therapy require gradual withdrawal of steroids otherwise they will experience severe glucocorticoid deficiency
describe the function of aldosterone synthase (aka CYP 11B)
- rate limiting step of aldosterone synthesis
- converts corticosterone into aldosterone in the z. glomerulosa
describe the signaling pathway of AG II
IP3/DAG, activates aldosterone synthesis
describe the signaling pathway of potassium on aldosterone
Increased ECF K concentration causes depolarization of the cell, which causes release of Ca and activation of aldosterone synthesis
describe the signaling pathway of aldosterone at target tissues
Enters the cell nucleus to modulate gene expression, which leads to an increase in enzymes/transport proteins
describe the MoA of aldosterone at the target tissue
- target tissue = distale tubule and collecting duct principal cells
- adds more Na and K channels at the lumen
- more Na is reabsorbed (+ H2O)
- more K is excreted into urine
what causes aldosterone release?
- JGA releases renin based on fluid status (hypovolemic, or hyponatremic)
- JGA releases renin (ENZYME)
- renin acts on angiotensinogen and converts it into AG I
- AG I -> AG II via ACE in the lungs
- AG II promotes aldosterone in z. glomerulosa
