Exam 3- Adrenal Cortex and HPA Axis Adrenal Medulla Flashcards
how is the inner portion of the adrenal glands innervated?
sympathetic preganglionic efferent nerves from hypothalamus
what does the adrenal cortex produce?
steroid hormones
what does the adrenal medulla produce?
catecholamines
what does the zona glomerulosa (outermost layer) produce?
mineralocorticoids
what does the zona fasciculata (middle layer) produce?
glucocorticoids
what does the zona reticularis (innermost layer) produce?
androgens
what mediates uptake of LDL-cholesterol complex by adrenocortical cells?
ACTH
what enzyme is important in adrenocortical hormone synthesis?
cholesterol desmolase: common first step in all adrenocortical hormone synthesis
what stimulates cholesterol desmolase?
ACTH, also dependent upon
what regulates glucocorticoid and androgen secretion?
hypothalamic-pituitary axis; negative feedback
what hormone secretion does the renin-angiotensin-aldosterone system control?
mineralocorticoid secretion
true/false: adrenocortical hormones are stored in granules so they are ready when they are needed
false: lipid-soluble so no intracellular stores
secretion of mineralocorticoids (aldosterone) is regulated by changes in ____________________________ and in _____________________
extracellular fluid volume
serum (extracellular) K+ levels
how does potassium affect aldosterone secretion?
acts directly on aldosterone-producing cells: higher K+ depolarizes cell membrane, leading to increase in intracellular calcium, stimulating cholesterol desmolase and aldosterone synthase
aldosterone has immediate and slow-onset effects in the kidney. these are:
prolongs opening time of Na+ channels: immediate
increases synthesis of Na+ channels and K+ channels: slow-onset
how do glucocorticoids affect glucose levels in blood?
increase them: catabolic and diabetogenic
true/false: all nucleated cells have glucocorticoid receptors
true
how do glucocorticoids affect carbohydrate, lipid, and protein metabolism?
increases carbohydrate metabolism
mobilizes protein from tissues- not liver
mobilizes fatty acids
are glucocorticoids immunosuppressive?
yes
how is cortisol immunosuppressive?
induces synthesis lipocortin, which inhibits phospholipase A2: prostaglandin and leukotriene synthesis suppressed
inhibits production interleukin-2 and proliferation T cells
inhibits release histamine and serotonin from mast cells and platelets
overall suppression adaptive and innate immune responses
do some other hormones need glucocorticoids to be effective themselves?
yes
from what are catecholamines synthesized?
tyrosine
what are the physiological effects of catecholamines?
elevated plasma glucose
mobilization fatty acids as source of energy
increased cardiac output
redistribution of blood supply
where are the adrenal glands located?
retroperitoneal
craniomedial to corresponding kidney
against roof of abdomen
what part of the adrenal gland functions as part of the autonomic nervous system?
medulla
what is the basis of specialization in each zone of the adrenal cortex?
presence/absence of enzymes that catalyze various modifications of the steroid nucleus
true/false: cholesterol is not stored inside the cell
false: is stored until it is required
what is the common precursor for all adrenocortical hormones?
pregnenolone
how is pregnenolone formed?
cholesterol desmolase converts cholesterol into it
what is a mineralocorticoid?
aldosterone
what are some glucocorticoids?
cortisol
corticosterone
What does corticotropin releasing hormone stimulate?
ACTH
how do adrenocortical hormones act?
bind to intracellular receptors and act through transcription of DNA and synthesis of new proteins
what are two specific transport proteins for adrenocortical hormones?
corticosteroid-binding globulin (CBG)
sex hormone-binding globulin (SHBG)
what are two non-specific transport proteins for adrenocortical hormones?
albumin and prealbumin
transport steroid hormones
how does angiotensin II stimulate aldosterone synthesis?
AT1 receptors on zona glomerulosa cells
Ca++ influx
stimulation cholesterol desmolase and aldosterone synthase
what stimulates the renin-angiotensin-aldosterone pathway and what does it do?
decrease in perfusion pressure to kidney
sodium retention at expense of potassium loss
does an increase or decrease in potassium stimulate aldosterone secretion?
increase
how is aldosterone metabolized and excreted?
conjugated to glucuronide in liver
excreted in urine and bile
what can prolonged stress result in in the adrenal cortex?
chronically elevated ACTH and tropic effect on adrenal cortex
what types of stress can lead to glucocorticoids being released?
trauma
infection
environmental temperature variations
psychological stress
how do glucocorticoids raise blood glucose levels?
stimulate hepatic gluconeogenesis
decrease glucose utilization and insulin sensitivity of tissues
mobilize amino acids from muscle for hepatic gluconeogenesis
true/false: glucocorticoids have a permissive role with keeping tissues responsive to other hormones
true: alpha 1 adrenergic receptors upregulated
insulin, glucagon, growth hormone, angiotensin II need cortisol
what catecholamine is secreted at the highest rate from the adrenal medulla?
epinephrine
what do the effects of epinephrine and norepinephrine depend on?
density of receptor subtypes and concentration of hormones
what stimulates the adrenal medulla to release catecholamines?
acetylcholine from sympathetic preganglionic nerve endings
what is the primary benefit of glucocorticoids?
ability to increase blood glucose
