15.6- The Kidney and Osmoregulation

Question 1

How is the amount of water lost in the urine controlled? (2 marks)

Answer 1

By ADH
in a negative feedback system

Question 2

Where is ADH produced and stored? (2 marks)

Answer 2

Produced- hypothalamus
Stored- pituitary gland

Question 3

How does ADH affect the distal convoluted tubule and collecting duct? (1 mark)

Answer 3

Increases the permeability

Question 4

Describe the mechanism of ADH. (5 marks)

Answer 4

1. ADH is released form the pituitary gland.
2. It is carried in the blood to the collecting duct.
3. Binds to the receptors on the cell membrane.
4. cAMP is formed and acts as a secondary messenger.
5. The cAMP triggers a cascade of events inside the cell

Question 5

Explain how ADH makes the collecting duct more permeable to water. (2 marks)

Answer 5

After the mechanism,
The vesicles (inside the cells) fuse with the cell membrane.
The membranes of the vesicles contain water channels.

Question 6

Other than water potential, what else is ADH used to monitor? (1 mark)

Answer 6

Blood pressure

Question 7

Explain how an increase in blood pressure is detected and how ADH can counteract this change. (4 marks)

Answer 7

A rise in blood pressure is often caused by an increase in blood volume.
This is detected by baroreceptors.
Less ADH is released.
This means the volume of water lost in the urine increases.
So the volume of blood decreases and blood pressure decreases.