Lecture 63-Adrenal Medulla And Cortex Flashcards
Where are the adrenal glands located?
Retroperitoneal cavity above each kidney
What are the two separate structural/functional glands of the kidney?
Medulla and cortex
What does the adrenal cortex produce?
Mineralcorticoids, glucocorticoids, androgens
What does the adrenal medulla produce?
Epinephrine and norepinephrine
What receptors does epinephrine act on?
ALL alpha- and beta- adrenergic receptors
What receptors does noraepinephrine act on?
Alpha 1 & 2, beta-1 receptors
What do chromaffin cells secrete?
Catecholamines (epinephrine and norepinephrine)
What is the half-life of chromaffin cells?
2 minutes
Where is the adrenal medulla located?
In the inner zone of the gland and surrounded by the cortex
Where does the adrenal medulla receive input from? What is it considered?
Receives input from sympathetic nervous system via preganglionic fibers originating in the thoracic spinal cord
**considered a specialized sympathetic ganglion
Where is epinephrine stored? And when is it released?
Stored in granules, and released when activated by SNS
Why does cortisol reach the medulla in such high concentrations?
Because it is made in the cortex
What enzyme converted NE -> EPI under the influence of cortisol?
Phenylethanolamine-N-methyltransferase (PNMT)
What is the predominant catecholamine synethesized?
Epinephrine (80%)
NE (20%)
Where does all EPI originate from?
Adrenal medulla
Where does most NE originate from?
Sympathetic nerve terminals and brain
(Only small amount from adrenal medulla)
What is the target tissue of catecholamines?
Muscle cells and liver
Where does the most metabolism of catecholamines occur in?
Liver and kidneys
The regulation of catecholamine secretion is responsible for which response?
FIGHT OR FLIGHT
What are the effects of catecholamines?
-increased heart rate, cardiac output, and blood pressure
-redistribution of blood towards skeletal muscle
-increased respiration
-increased blood glucose
-blood shunted AWAY from GIT
-increase lipolysis and possible gluconeogenesis
What are the zones AND major hormones of each zone in the adrenal cortex?
- Zona glomerulosa
A.) aldosterone - Zona Fasciculata
A.) cortisol (in humans, dogs, cats, horses, pigs, sheep, cattle)
B.) corticosterone (in rat, mouse, rabbit) - Zona reticularis
A.) androgen precursors-> converted to testerogen and estrogen in peripheral
B.) DHEA
C.) Androsterone
What is the precursors for all steroids?
Cholesterol
What is the first step of steroid hormone production? Which enzyme plays a big role? Which zones contain this step?
Conversion of cholesterol to pregnenolone
Cholesterol Desmolase is the enzyme that makes this conversion possible !
All layers or zones contain this enzyme !!!!!!!!
What does the direction of the hormone pathway depend on?
Presence/absence of enzymes to catalyze modifications
Where is the main site of production for mineralcorticoids (such as aldosterone)?
Adrenal cortex: Zona glomerulosa
What does the production of mineralcorticoids REQUIRE?
Aldosterone Synthase
ACTH to stimulate cholesterol desmolase
Aldosterone is long OR short term regulation of blood pressure?
Long-term
What type of pattern does aldosterone display?
Diurnal pattern
What is the half life of aldosterone?
20 minutes
How does the primary regulation of aldosterone occur? (2)
Via changes in ECF volume via renin angiotensin II-aldosterone system AND changes in blood pressure
How is aldosterone transported in blood?
Aldosterone-binding globulin, transcortin, albumin
What stimulates synthesis of aldosterone? WHat is considered the mediator in aldosterone secretion?
Angiotensin II
What are the two things that the renin-angiotensin II-aldosterone system DECREASES? What is one thing this system INCREASES? What is the ultimate end goal of this system?
Decreases = ECF volume, renal blood perfusion pressure
Increases= renin secretion by kidney
End goal = stimulates Na reabsorption by kidney to restore ECF volume
When regulating aldosterone secretion there is an increase in blood K+ concentration. This results in deporliazation of adrenal cells to open which channel? The opening of this channel stimulates secretion of what? Which ultimately results in excretion of what?
Depolarization adrenal cells = opening Ca channels = stimulate aldosterone secretion = increases K+ excretion in kidneys
Where are glucocorticoids (cortisol) produced?
Adrenal cortex: Zona fasciculata
What is required to produce glucocorticoids?
ACTH to stimulate cholesterol desmolase
What is the half life of cortisol?
60-90 minutes
What axis is cortisol regulated by?
Hypothalamic-pituitary-adrenal axis
How is cortisol transported in blood?
By transcortin
What is cortisol metabolized by? Where is it excreted?
Metabolized by the liver
Excreted in urine using glucuronides
What are two factors that influence ACTH secretion?
Stimulators and inhibitors
What are examples of stimulators?
Stress, low cortisol, ADH
What are examples of inhibitors?
High cortisol, exogenous steroids, somatostatin, dopamine
What two things inhibit CRH release?
Cortisol and ACTH
ACTH has a ___ loop feedback to inhibit CRH release. Cortisol has a ____ loop feedback to block CRH release.
ACTH has short loop feedback
Cortisol has long loop feedback
What does administration of exogenous corticosteroids create? And then result in?
Creates negative feedback
Resulting in adrenal gland atrophy
