section 3 (6) outline the role of the hormones, aldosterone and ADH (anti-diuretic hormone) in the regulation of water and salt levels in blood

Question 1

Where is aldosterone produced?

Answer 1

• adrenal glands (adrenal cortex)
• produced when there is a decrease in sodium ions in the bloodstream: also when there is a decrease in blood pressure and volume.
• decrease in blood volume/ pressure → release of
  enzyme renin → release of aldosterone
• reaches kidney from the adrenal gland via bloodstream

Question 2

What effect does aldosterone have?

Answer 2

• causes convoluted tubules to actively reabsorb more sodium ions
• increases the nephrons permeability to sodium ions (especially loop of Henle)
• decreases potassium ion reabsorption
• as sodium ions are reabsorbed by capillaries, salt is retained
• creates an osmotic pull for water, which is then also reabsorbed in greater volumes and hence increases blood pressure and volume → fall in solute concentration in water

Question 3

where is ADH produced?

Answer 3

• neurosecretory cells in the hypothalamus, stored and released from the posterior pituitary gland
• produced when the hypothalamus detects a rise in blood solutes → decrease in water concentration
• reaches kidney from pituitary gland via the bloodstream

Question 4

what does ADH do?

Answer 4

• Increases the permeability of the distal convoluted tubules and collecting ducts to water → more absorption of water
• also increases the permeability of collecting duct walls to urea allowing more urine to be produced.
• ADH is suppressed by alcohol