Lecture 69 Flashcards
located in the retroperitoneal cavity above each kidney
adrenal glands
the adrenal gland consist of two separate glands known as
Medulla and cortex
Adrenal cortex produces
mineralocorticoids, glucocorticoids, androgens
Adrenal medulla produces __________ neurocrines
Epinephrine and norepinephrine
the adrenal medulla is located in the __________ of the gland surrounded by the cortex
inner zone
The adrenal medulla receives input from SNS via preganglionic fibers originating in the thoracic spinal cord- considered a
specialized sympathetic ganglion
Chromaffin cells secrete catecholamines:
EPI and NE
Half life of catecholamines
2 minutes
catecholamines are released into blood- medulla has a
very dense supply
Epi acts on __________ adrenergic receptors
ALL alpha and beta
NE acts on alpha 1 and 2, and
Beta-1 receptors
zona reticularis releases
androgens
zona fasciculata releases
Glucocorticoids
Zona glomerulosa releases
mineralocorticoids
catecholamines are
water-soluble substances
predominant catecholamine synthesized is __________ (80 percent)
Epi
How much NE is released?
20 percent
Enzyme phenylethanolamine-N-methyltransferase (PNMT) converts NE to epi under?
the influence of cortisol
__________ converts NE to EPI
PNMT
Under the influence of cortisol epi is able to reach medulla in increase conc and upregulates
PNMT
Epi is stored in granules and released when activated by
SNS
All epi originated from
Adrenal medulla
Most NE originates from sympathetic nerve terminals and brain
only small amount from adrenal medulla
Target tissue of catecholamines:
Muscle cells and liver
Most metabolism of catecholamines occurs in
liver and kidneys
Alpha 1 receptors activate production of DAG and IP3 leading to an
increase in intracellular calcium ions
catecholamines are secreted in response to fight or flight in response to:
Anticipation of danger, trauma, pain etc.
Catecholamines increase
heart rate, cardiac output and BP
Zona glomerulosa major hormone
Aldosterone
Zona fasciculata major hormone
Cortisol in humans, dogs, cats, horses, sheep and cows
Corticosterone in rats, mice and rabbits
Zona reticularis major hormones
androgen precursors: converted to testosterone and estrogen in peripheral tissues
Zona reticularis major hormone DHEA
Dehydroepiandrosterone and androstenedione
Zones of adrenal cortex Serve a wide variety of physiological functions including
Blood glucose regulation, pretin turnover, fat metabolism, Na/K/Ca balance, Cardiovascular maintenance
Precursor for all steroids is
Cholesterol
Cholesterol is from
circulation (diet), some from de novo synthesis
Steroids are catalyzed by __________ systems in mitochondria and endoplasmic reticulum
Cytochrome p450
First step (rate-limiting) of steroid: Conversion of cholesterol to
pregnenolone
Steroid hormone: nothing is stored in the cell so conversion via cholesterol __________ is a critical step
desmolase
T/F: All layers of adrenal cortex have cholesterol desmolase
T
__________ activates cholesterol desmolase. (irs from anterior pituitary)
ACTH
Direction of pathway for steroids depends on presence/absence of enzymes to
Catalyze modifications
The zona glomerulosa requires ACTH to simulate cholesterol desmolase and requires
aldosterone synthase
Half life of aldosterone
20 mins
Aldosterone has a long-term regulation of
blood-pressure
Alodsterone exhibits a __________ lowest at midnight and highest before awakening
Diurnal pattern
Aldosterone: Primary regulation occurs via changes in ECF volume via
RAAS and changes in blood potassium
how is aldosterone transported in the blood
Aldosterone- binding globulin, transcortin, albumin
In making aldosterone corticosterone used aldosterone synthase and __________ is required to stimulate it
Angiotensin 2
Mediator for regulation of aldosterone is
angiotensin II
Decrease in ECF volume causes a decrease in renal blood flow and cause the kidney to increase __________?
Renin
Aldosterone stimulates Na reabsorption by kidney to restore
ECF volume
aldosterone depolarizes adrenal cells to __________ to stimulate aldosterone secretion
open Ca channels
Once the adrenal cells open Ca channels aldosterone secretion increase __________ in the kidneys
K+ excretion
Zona fasciculata produces glucocorticoids, mainly cortisol. it requires __________ to stimulate cholesterol desmolase
ACTH
Zona fasciculata: First step catalyzed by
17 alpha-hydroxylase
If 17 alpha-hydroxylase is blocked you can still get
corticosterone (generally no deleterious effects)
zona fasciculata: final enzyme in pathway ( 11 beta-hydroxylase) converts __________ to cortisol
11-deoxycortisol
half life of cortisol
60-90 mins
Cortisol is regulated by
hypothalamic-pituitary- adrenal axis
ACTH is released from anterior pituitary and CRH is released by
Hypothalamus
how is cortisol transported in blood?
By transcortin
Cortisol is metabolized by liver and excreted how?
By kidneys using glucuronides
CRH and ACTH pulsatile in humans and peak when?
2 hours before awakening
CRH and ACTH is __________ throughout the day for a dog
episodic
stimulators of ACTH
stress, hypoglycemia, infections/fever, low cortisol and ADH
inhibitors of ACTH
high cortisol, exogenous steroids, somatostatin, dopamine
HPA axis of cortisol: Long loop feedback (Minutes) to inhibit
ACTH release (blocks CRH action)
Slow feedback of cortisol HPA axis takes __________ to inhibit ACTH synthesis
hours
Long loop feedback to block CRH release from
hypothalamus
HPA axis of ACTH : __________ inhibits CRH release
short loop feed back
administration of __________ creates artificial negative feedback resulting in adrenal gland atrophy
exogenous corticosteroids
cortisol binds type II __________receptor in cytosol
glucocorticoid
receptor-hormone complex moves into nucleus and binds another receptor on
DNA (DNA response element)
Cortisol at tissue level activate
gene transcription and translation