1. Osmoregulation

2. Spec (d) the control of the water potential of the blood
To include the role of osmoreceptors in the hypothalamus, the posterior pituitary gland, ADH and its effect on the walls of the collecting ducts.

3. Learning Objective Success Criteria
Explain the control of water potential of the blood
Explain how the water potential of the blood is controlled, including the role of osmoreceptors in the hypothalamus, the posterior pituitary gland, ADH and its effect on the wall of the collecting duct

4. State whether water is gained or lost from each item
Urine
Food
Drink
Metabolism (e.g respiration)
Faeces
Sweat
Exhaled air

5. Osmoregulation
Osmoregulation is the control of water levels and salt levels in the body.
Correct balance must be maintained to prevent problems with osmosis

6. Permeability of the Collecting Duct
In the absence of ADH the collecting duct wall is impermeable to water
The walls of the collecting duct respond to the level of antidiuretic hormone (ADH) in blood.

7. The effect of ADH on the collecting duct wall7

8. TASK: Turn the Following points into a storyboard
1. ADH is detected by cell surface receptors
2. Enzyme controlled reactions
3. Vesicles containing water permeable channels (aquaporins) fuse to membrane
4. More water can be reabsorbed

9. Osmoreceptors Neurosecretory cells Osmoreceptor - Ψ H20 H20
The water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
Negative water potential causes the OR to lose water and shrink which stimulates the NS cells
Neurosecretory
cells
Osmoreceptor
- Ψ
H20
H20
Osmoreceptor
ADH

10. Neurosecretory cells ADH ADH ADH ADH Hypothalamus
Posterior Pituitary Gland
When neurosecretory cells are stimulated they send action potentials down their axons that cause the release of ADH
ADH
ADH
ADH
ADH

11. ADH
ADH then enters the blood capillaries near the PPG and acts on the cells of the collecting ducts

12. Negative Feedback Once the water potential rises less ADH is released
ADH is slowly broken down therefore there will be less in the blood so collecting ducts receive less stimulation

14. TASK
Complete the flow diagram

15. Extension Activity
Biofactsheet

16. Plenary: PPQs

17. PPQ – ADH 2013
See Print out

18. Markscheme

19. Markscheme continued