adrenal gland hormone

Question 1

what does the zona glomerulosa do

Answer 1

• retains Na- and extrudes K+
• ensures electrolyte balance is maintained

Question 2

what is osmolarity maintained at

Answer 2

300mOs/L

Question 3

how is aldosterone synthesised

Answer 3

• the adrenal cortex synthesises aldosterone from cholesterol
• glomerulosa cells exclusively (they are the only ones which contain aldosterone synthase)

Question 4

what is the function of aldosterone

Answer 4

it stimulates the kidney to reabsorb Na+ and water and to enhance K+ secretion (it changes K+ to Na+)

Question 5

how does aldosterone work

Answer 5

• it acts by modulating gene expression after binding to the mineralocorticoid receptors (MRs)

Question 6

what stimulates the production of aldosterone

Answer 6

ACTH, extracellular [K+] and [Na+], and ANG II

Question 7

what is the mechanism of action of aldosterone

Answer 7

• increased transcription of the Na/K pump, so augmenting distal Na+ reabsorption
• increased expression of apical Na+ channels and an Na/K/Cl cotransporter so increasing Na+ reabsorption and K+ secretion

Question 8

how is aldosterone synthesis regulated

Answer 8

• Na+ and H2O levels feedback through the RAS
• high extracellular K+
  – in blood
  – depolarises glomerulosa cells
• ACTH
  – stresses induces release from AP
  – binding to MC2R stimulates Ca2+ influx