Adrenals Flashcards
bilateral structures
situated above the
kidneys
adrenal glands
makes up more than
¾ of the adrenal mass
the cortex (outer region) of the adrenal glands
inner region of the adrenal glands
medulla
The cortex is divided into 3 zones:
- Zona Reticularis
- Zona Fasciculata
- Zona Glomerulosa
is a specialized tissue that carries out hormone-activity and regresses shortly after birth
fetal zone
two zones of fetal cortex
fetal zone (80% of mass)
definitive zone
Blood flows from
the adrenal cortex into the medulla
have one of
the highest rates of blood flow in the body
adrenal glands
are steroidogenic, meaning they secrete steroid hormones
Adrenal cortical cells
salt/water balance and blood pressure
Mineralocorticoids (aldosterone)
sugar and energy metabolism
Glucocorticoids (cortisol; corticosterone)
secondary sex characteristics
Sex steroids (DHEA, androstendione)
Rate-limiting
step in steroid
biosynthesis
STAR
and P450scc in the breakdown of cholesterol
The specific
hormone made
depends on
the enzymes present in the cell
A major function of the adrenal gland is to
respond to stress
energy mobilization
produced in the medulla
Catecholamines (epinephrine, norepinephrine)
an event that threatens homeostasis and triggers allostatic responses
stress
maintenance of
stable, constant bodily
conditions within an optimal range to sustain life.
homeostasis
process of achieving homeostasis. Adrenal hormones are one of the primary mediators.
allostasis
short term, relatively easy to recover from.
acute stressors
long term; recovery not complete. Body may “adapt” with a new set point.
chronic stressors
The process your body goes through when you are exposed to any kind of stress, positive or negative. It has three stages: alarm, resistance, and exhaustion
general adaptation syndrome
steps of general adaptation syndrome
- alarm - acute stressor is identified and and body is in a state of alarm. starts to produce fight or flight response
- resistance - body begins to cope if stressor persists.
- exhaustion - if resources are depleted and the body is unable to maintain normal function
Glucocorticoids are regulated by the
HPA axis
Catecholamines are regulated by the
sympathetic nervous system
what classification are cortisol and corticosterone
glucocorticoids
what classification are epinephrine and adrenaline
catecholamines
what is responsible for the fight or flight response
Catecholamines and the sympathetic nervous system
responsible for rest and digestion
parasympathetic system
are modified
neurons that lack
dendrites and axons
stress
Chromaffin cells
Gaq coupled receptor that stimulates IP3/calcium
Higher affinity for norepinephrine
Alpha Adrenergic Receptors
Stimulates smooth muscle contraction (constricts blood flow, pupils dilate, Pyloric sphincter in stomach
constricts to reduce digestion)
Alpha Adrenergic Receptors
Gas coupled receptor that stimulates cAMP
Higher affinity for epinephrine (has an E)
Beta Adrenergic Receptors
Stimulates smooth muscle relaxation in the lungs, blood flow, and GI tract
Beta Adrenergic Receptors
beta receptor agonist
EpiPen (epinephrine)
instantaneous,
involves catecholamines
Sympathetic nervous
system
slower,
involves glucocorticoids
HPA axis
are the primary glucocorticoids, and their
main function is to mobilize energy
Cortisol and corticosterone
is the primary regulator of glucocorticoid release
HPA axis
primary glucocorticoid in
most mammals, including humans, and fish
cortisol
primary glucocorticoid in rodents, birds, reptiles, and amphibians
Corticosterone
Cortisol circulates in the blood bound to carrier proteins, mainly
corticosteroid-binding globulin (CBG, also known as transcortin)
don’t create stress or prepare you for it; they help you recover from stress
Glucocorticoids
Enhance Memory Consolidation
Glucocorticoids
Excessive secretion of glucocorticoids (typically due to adrenal tumor or
glucocorticoid medications)
Symptoms:
* Visceral fat gain
* High blood sugar
(develop diabetes)
Cushing’s Syndrome
Deficient in glucocorticoid secretion (due to injury to adrenal tissue)
- Excessive ACTH (no negative feedback)
to Hyperpigmentation - Low blood sugar
- Weight loss
Addison’s Disease
zona glomerulosa tissue produces
Mineralcorticoids
zona fasciculata tissue produces
Glucocorticoids
zona reticularis tissue produces
sex steroids
A major function of the
adrenal gland is to
regulate salt and water balance
depends on the maintenance of water-sodium balance
blood pressure
the primary mineralcorticoid
Aldosterone
- Increases sodium reabsorption
- Increases potassium excretion
aldosterone
Specificity is achieved in aldosterone-responsive cells by having
11βHSD2
Principle regulators of aldosterone production
- Angiotensin II (Renin–Angiotensin system)
- High potassium levels (Hyperkalemia)
A renal (kidney) mechanism that governs
blood pressure (BP) homeostasis, as well
as fluid and salt balance
Renin-Angiotensin System
3 hormones collaborate to regulate BP:
Aldosterone, ADH, and Angiotensin II
Liver constitutively
releases Angiotensinogen
Step 1 of the Renin-Angiotensin system
Kidney detects a drop in
blood pressure and
secretes renin (an enzyme)
Step 2 of the Renin-Angiotensin system
secreted by juxtaglomerular cells in response to:
* Low BP detected by baroreceptors in arterioles
* Stimulation of beta adrenergic receptors
* Low sodium levels detected by macula densa cel
renin
Renin and Angiotensin-
converting enzyme (ACE) catalyze the creation of Angiotensin II
Step 3 of the Renin-Angiotensin system
Angiotensin II does the following:
- Constricts blood vessels
- ADH secretion
- Aldosterone secretion
ADH is secreted by the
posterior pituitary and
stimulates the kidneys to
reabsorb water
Step 4 of the Renin-Angiotensin system
ADH increases water reabsorption by
inserting
aquaporins
Aldosterone is secreted by the adrenal gland and
stimulates the kidney to
reabsorb sodium
step 5 of the renin-angiotensin system
High blood pressure is the
negative feedback signal
that regulates this system
step 6 of the renin-angiotensin system
stimulates potassium
secretion in response to high potassium (hyperkalemia)
aldosterone
directly monitored by
adrenal glomerulosa cells
potassium levels
are the primary steroids,
and their main function is to regulate development of secondary sex
characteristics
androgens
Caused by a genetic mutation in an enzyme
needed to make one or more of the adrenal
hormones – usually detected in infancy
Classic Congenital Adrenal Hyperplasia (CAH)
Results in the overproduction of hormone precursors to compensate
Classic Congenital Adrenal Hyperplasia (CAH)
what is responsible for 95% of Classic Congenital Adrenal Hyperplasia
A 21-hydroxylase (CYP21A2) deficiency
Effects of Classic Congenital Adrenal Hyperplasia
- Can’t make glucocorticoids or aldosterone
- Overproduce sex steroids
symptoms of CAH
Simple-virilizing symptoms (early puberty for male and female. normal genitalia for males, enlarged clit for females)
Can’t retain salt or water leads to excessive dehydration and low blood pressure
CYP21A2 function
Mutation causes CAH
11βHSD2 function
Inactivates cortisol, allowing mineralcorticoid receptor specificity
CYP11B2
Helped animals balance water and transition to land
STAR & p450scc function
Rate-limiting steps in steroidogenesis
