physiology

Question 1

aldosterone - what is it? where produced? role? mode of action?

Answer 1

main mineralocorticoid hormone, produced by adrenals.

role - Na conservation in kidneys → regulates BP, Na + K levels

MoA - acts on distal tubules + collecting ducts → Na absorption + K excretion

→ influences water retention or loss, BP + blood volume

Question 2

ACEis - MoA in HTN and HF?

Answer 2

HTN:
act on RAAS (inhibits ACE which converts AI → II. AII causes vasoconstriction + aldosterone release)
→ decrease aldosterone → reduce Na + water retention, increase K retention
→ relaxes vessels
→ decreased BP + lower O2 demand

HF:
relaxation of vessels makes it easier for heart to pump around body (decreased afterload)

Question 3

CCBs

Answer 3

entry of Ca into muscle cells of heart + arteries is needed for:

1) conduction of electrical signal from muscle cell to muscle cell of heart, + signals heart to contract
2) muscle cells to contract + pump blood
3) arteries - entry into artery muscle cells → constriction

CCBs:
block entry of Ca into muscle cells of heart + arteries →
1) dilation of arteries - reduced BP + afterload, + more O2 to heart
2) decrease force of contraction of muscle cells - this, combined with reduced afterload, decreases O2 requirement by heart
3) reduced O2 demand + increased O2 delivered helps prevent angina
4) slow electrical conduction in heart → correct abnormal tachyarrythmias

Question 4

spironolactone - MoA?

Answer 4

K-sparing diuretic
reduce fluid retention, oedema + sx of HF
also decreases BP by releasing fluid from body while retaining K

Question 5

explain the RAAS

Answer 5

1) renal blood flow decreased → juxtaglomerular cells convert prorenin → renin + secrete to blood
2) renin converts angiotensinogen → angiotensin I
3) ACE (on vascular endothelial cells) converts angiotensin I → angiotensin II
4) angiotensin II →:
a) vasoconstriction → BP raised
b) aldosterone secretion from adrenals, which → Na + H2O resorption by renal tubules + K excretion (to maintain e- balance) → increase fluid volume → increases BP
c) stimulates pituitary to secrete ADH, which also acts on kidneys to increase water retention

Question 6

vasopressin (ADH) - where made? what stimulates its release? roles?

Answer 6

angiotensin II → ADH release
ADH made in hypothalamus + released from pituitary. roles:

1) vasoconstriction
2) main role - stimulate reabsorption of H2O
3) acts on CNS to increase appetite for salt + stimulate sensation of thirst