Adrenal gland Flashcards
Location of adrenal gland
located above the kidneys
what are two regions of adrenal gland
cortex and medulla
adrenal cortex
- most of the weight 90%
- derived from mesodermal
adrenal medulla
- derived from subpopulation of neural crest cells
- **NE and E comes from crest cells which are neurotrasnsmitters too. They are part of the post ganglion of sympathetic nervous system
- remaining 10% of mass
3 zones of cortex
1) zona glomerulosa outer
2) zona fasciculata middle
3) zona reticularis inner
zona glonerulosa
outer region
- where aldosterone comes from
- abundant of smooth ER because it produces steroid
zona fasciulata
- middle region
- look like chords
- produce glucocorticoids, cortisol, corticosterone, and the androgens (DHEA and DHEA sulfate)
- has lipid droplets
- ACTH
zona reticularis
- inner region
- develops postnatally
- recognizable at 3 years
- also produces glucocorticoids and androgens
Hormones of cortex
the cortex synthesizes the adrenal steroid hormones reasponse to hypothalamic-pituitary adrenal hormome stimulation
- derivied from chloesterol
- glucocorotioids, mineralcocorticoids, and androgens (cortisone, aldosterone)
Hormones of medulla
- synthesizes catecholamines in response to direct sympathetic stimulation
- derived from L-tyrosine
- epinephrine and norepinenphrine
blood supply of adrenal glands
Blood flows from outer to go inner through sinusoid system (type of cappillary, which are made of endothelial cells, that have spaces in between for larger proteins to go into venous system)
- Blood supply to the adrenal glands from the superior, middle, and inferior suprarenal arteries.
- form a capillary network arranged so that blood flows from the outer cortex toward the center area, following a radially oriented sinusoid system.
- direction of blood flow controls the access of steroid hormones to the circulation and concentrates the steroid hormones at the core of the adrenals,
sinusoid are also found in
- liver: because of albumin
- bone marrow: because of RBC and WBC
acute regulation
- one way of stimulating production
- results in the rapid production of steroirds in repsonse to immediate need and occurs within minutes of the stimulus
chronic stimualtion
- such as that which occurs durrong prolonged starvation and chronic disease
- involed the synthesis of enzymes involved in steroidogenesis to enhance the synthetic capacity of the cells.
hypothalamic-pituitary adrenal axis
glucocorticoid synthesis and release part 1
- the pulsate release of cortisol us under direct stimulation by adrenocoritocoptrop hormones (ACTH) released from anterior pituitary
- aldosterone and or cortisol is then released
- cortisol release follows circadian rhythm
hypothalamic-pituitary adrenal axis
glucocorticoid synthesis and release part 2
- CRH is repsonse to stress is released at medien eminance. picked up by the primary plexus of hypohyseal protal system travels to anterior pit. coritcotrrophs pick up the signals in anterior pit. They increase cyclin andenosine (coupled to alpha s)
- ACTH is released and targets adrenal cortex zona fascilualta and glomaerosa.
- increase in adenate cyclate which is g protein alpha s involved
products:
increase in cholesterol availibility for hormone synthesis
increase synthesis of STAR, enzyme involved in the transport of cholesterol into the inner mitochondrial membrane.
cortisol is
lyphophilic - mostly insoluable in water
- found in conjugared form
- bound to carrier proteins
- inactived and eliminated in liver and kidney
- liver generates more soluable form leading to easier excretion
11β-hydroxysteroid dehydrogenase type I
- enzyme
- type 1 amplifiy cortisol activity
converts cortisone back to its active form cortisol
expressed in liver, adipose tissue, lung, skeletal muscle, vascular smooth muscle, gonads, and the central nervous system.
Amplifies glucocorticoid action
11β-hydroxysteroid dehydrogenase type II
- enzyme
- in areas where aldosterone is needed active
- *kidneys
- contributes to mineralcorticoid hormone effects
- converts cortisol in into cortisone, its less active metabolite
-decreases glucocorticoid action
renin-angiotensinn aldosterone system
Decrease in plasma volume –> renin is released becuase it is sensed by cells of nephon
renin cleaves (CUT) angiotensingen into angiotesnsion I
ACE enzyme that cleaves angiotension 1 to 2
angiotension 2 targets adrenal cortex
in response aldosterone is produces
aldosterone effects: targeting collecting ducts, increase NA+ absorption, increase K+ absorption,
which increases plasma volume/ blood pressure
angiotension2 also produces vasal constriction
look at slide 15
what else triggers aldosterone production
Potassium- also a major physiologic stimulus for aldosterone production, (classic example ofhormone regulation by the ion it controls)
Aldosterone is critical in maintaining potassium homeostasis by increasing K+excretion in urine, feces, sweat, and saliva, preventing hyperkalemia during periods of high K+intake or after K+release from skeletal muscle during strenuous exercise.
In turn, elevations in circulating K+ concentrations stimulate the release of aldosterone from the adrenal cortex.
too much potassium trigers aldosterone which will get rid of it
how are mineralcorotiocuds metabolized
Circulating levels much lower than glucocorticoids- Secretion can be increased 2- to 6-fold by sodium depletion or by a decrease in the effective circulating blood volume, such as occurs with ascites.
Binding of aldosterone to plasma proteins is minimal, resulting in a short plasma half-life of approximately 15–20 minutes.
Aldosterone is metabolized in the liver to tetrahydroglucuronide derivative and excreted in the urine.
adrenal androgens
produced by zona reticularis including DHEA and DHEAS
DHEA is the most abundant circulatinghormone in the body and is readily conjugated to its sulfate ester DHEAS.
Production of DHEA is controlled byACTH.
metabolism of adrenal androgens
The adrenal androgens are converted into androstenedione and then into potent androgens orestrogensin peripheral tissues.
