Adrenal cortex (dave's notes only so far) Flashcards
What does the adrenal cortex secrete?
Glucocorticoids, mineralocorticoids, and ANP
Where are glucocorticoids secreted from?
From the zone fasciculata and reticularis of the adrenal cortex, C21, primary glucocorticoid is cortisol
What is cortisol synthesised from? What controls this?
Cortisol is synthesised from cholesterol de novo on an as needed basis. Under the control of ACTH
What pathway leads to ACTH release?
CRH from the hypothalamus stimulates corticotrophs to release ACTH from the anterior pituitary
What stimulates ACTH release?
Stress, hypoglycaemia
What inhibits ACTH release?
Cortisol (negative feedback)
What is the action of ACTH?
ACTH binds a specific receptor, couples a g-Protein which increases cAMP, this provides cholesterol as a substrate. ACTH also has a trophic action on the adrenal cortex
Describe cortisol transport and give half life of cortisol
Cortisol is bound to CBG (transcortin) (75%), and albumin (15%), and 10% is free. Half life is approximately 90mins.
What is glucocorticoids/cortisol metabolised into? How is it excreted?
Cortisol is metabolised into cortisone. It is inactivated in the liver, conjugated, and excreted by the liver.
What is the action of glucocorticoids (mainly cortisol)
Cortisol acts via a receptor to the nucleus, stimulates transcription and increases synthesis of mRNAs
What is the effect of cortisol /?glucocorticoids?
Increased protein catabolism, increased gluconeogenesis, anti-insulin effect, increases blood glucose
What does cortisol suppress?
ACTH via negative feedback
What requires cortisol to be able to work?
Other hormones e.g. adrenaline, glucagon, catecholamines ->bronchodilatation?
Give four other effects of cortisol
Anti-inflammatory, anti allergy, increases platelets, neutrophils and erythrocytes, and increases Hcl and pepsin secretion
How does cortisol have an anti-inflammatory and anti-allergic effect?
It decreases eosinophils, decreases antibody production and ?? decreases ?lymphoid organs.
What is the primary mineralocorticoid?
Aldosterone - most important
Where is aldosterone secreted from?
Aldosterone is secreted from the zone glomerulosa, ???C21 wtf,
What stimulates aldosterone secretion?
Decreased ECF volume, Angiotensin II, and ACTH and K+ also have small effects on aldosterone secretion
How does a decrease in ECF volume lead to aldosterone secretion?
Decreased ECF -> JG cells -> renin release->lysis ??angiotensinogen ->ANGT 1 ->ACE (lung) ->ANGT II
How does angiotensin II lead to aldosterone secretion?
ANGT II -> stimulates adrenal to produce aldosterone ??via g-protein ->PpC
What is the transport and metabolism of aldosterone?
Aldosterone is loosely bound to albumin, and is inactivated by conjugation and reduction
What are the effects of aldosterone?
Aldosterone binds the aldosterone receptor causing synthesis of new mRNA leading to ?Na/K+ ATP-ase
What are the effects of aldosterone on the kidney?
Aldosterone increases distal tubule reabsorption of Na in exchange for K+ and H+, therefore causes Na retention and K+/H+ loss
What are the effects of aldosterone on the large bowel?
Similar to its effects on the kidney?
What is ANP?
Atrial natriuretic peptide, a 28 amino acid protein found in the atria
What increases secretion of ANP?
Increased CVP (and vice versa). Short half life.
What is associated with a fall in aldosterone?
A rise in ANP
What are the actions of ANP?
- ANP causes natriuresis? through mesangial cells affecting the GF area, or through tubular Na handling
- Lowers the BP by inhibiting several vasoactive substances
- decreases release of vasopressin
- decreases release of renin
What are two congenital adrenal defects?
21 hydroxylase deficiency, 11 hydroxylase deficiency
What does 21 hydroxylase deficiency cause?
Sodium loss
What does 11 hydroxylase deficiency lead to?
Hypertension and increased sodium
