Role of hormones in osmoregulation

Question 1

Why may the water potential of the blood decrease?

Answer 1

Little water consumed

Much sweating

Large ion intake

Question 2

Describe the process of the bodys response to a fall in water potential of the blood

Answer 2

Osmoreceptors in the hypothalamus of the brain shrink
This causes ADH production
ADH is passed to the posterior pituritary gland and secreated to capillaries
ADH passes from blood into kidney
ADH bind to receptors on surface of collecting duct, activating the enzyme phosphorylase
Phosphorylase causes vesicles that contain aquaporins to fuse with the cell surface membrane
This increases collecting ducts permeability to water and urea
This causes more water to leave the collecting duct by osmosis and move back into the blood, preventing drop in water potential
More concentrated urine is formed
Nerve impulses then sent to thirst centre in the brain

Question 3

Describe the process of the bodys response to a rise in water potential of the blood

Answer 3

Osmoreceptors detect rise in water potential and reduce impulses to posterior pituitary gland , reducing secretion of ADH
Less ADH reduces collecting duct permeability to water and urea
Less water reabsorbed into blood from collecting duct
More dilute urine is formed

Question 4

What causes a rise in blood water potential?

Answer 4

Large consumption of water

Lack of salts intake