6D: Regulation of water

Question 1

What is osmoregulation?

Answer 1

The homeostatic regulation of osmolality in the body via the alteration of water and solute balance.

Question 2

What is water useful for?

Answer 2

• urine production
• removal of heat from sweat evaporation
• maintenance of blood volume
• protect of brain + CNS (cerebrospinal fluid)

Question 3

What receptors are involved with a decrease in water levels?

Answer 3

Baroreceptors detect fall in blood pressure + volume
Osmoreceptors detect increase in osmolality

Question 4

What receptors are involved with an increase in water levels?

Answer 4

Baroreceptors detect increase in blood pressure + volume
Osmoreceptors detect decrease in osmolality

Question 5

What is the modulator, effector and response for when water levels are low?

Answer 5

M: Release of renin from kidney cells, causing release of aldosterone
E: Activation of sodium-potassium pumps, increasing reabsorption of sodium
R: Increased reabsorption of water from kidney filtrate.

M: Hypothalamus causes release of ADH from posterior pituitary gland
E: Aquaporins inserted into DCT + collecting ducts
R: increased reabsorption of water from kidney filtrate
E: stimulation of cells in thirst centre
R: increase in fluid consumption

Question 6

What is the modulator, effector, and response for when water levels are high?

Answer 6

M: Hypothalamus suppressed the release of ADH from the posterior pituitary gland
E: Decreased insertion of aquaporins in DCT + collecting duct
R: Decrease in water reabsorption from urine
E: Thirst centre is suppressed
R: Decrease in fluid consumption

Question 7

What is ADH, and its function?

Answer 7

Anti-diuretic hormone increases permeability of collecting duct wall, making it more porous, therefore more water moves out of DCT/collecting duct by osmosis into bloodstream (increasing water potential)