1. What’s the link?

2. ADH and the Kidney

3. Lesson Objectives When is ADH released into the bloodstream?
How does ADH effect the collecting duct?
How can alcohol and caffeine affect production of urine?

4. On average, how much urine does a person produce a day?
A: litre
B: litres
C: litres
D: Over 2.5 litres

5. Osmoregulation
Osmosregulation is the control of water and salt levels in the body.
Water potential Ψ is…
…a measure of the relative tendency of water to move from one area to another, represented by the Greek letter Ψ (Psi). (how “watery” a fluid is)

6. Water balance
Our bodies control the amount of water in our blood and tissues through the endocrine system (hormonal system)
Like thermo-regulation, water balance is a negative feed back system that relies on the hypothalamus in the brain.
Anti Diuretic Hormone (ADH) is released in the blood to control how much water the kidneys release in urine.

7. Water balance Healthy kidneys filter the blood to:
Remove waste products (from metabolism of the food we eat and body cells).
Remove excess fluid to balance fluid levels in the body

8. The amount of water in the blood must be kept more or less the same all the time to avoid cell damage as a result of osmosis. There has to be a balance between the amount of water gained (from your diet though drinks and food and the water produced by cellular respiration) and the amount of water lost by the body (in sweating, evaporation, faeces and urine). This is achieved by the action of the hormone ADH (anti-diuretic hormone).

9. 9

12. What is this?
The pituitary gland

14. ADH goes to, and acts on, the collecting ducts in the kidneys

15. Control of water hypothalamus Kidneys excrete more water in urine
Kidneys excrete less water in urine
+ water in blood
- water in blood
Pituitary gland produces less ADH
Pituitary gland produces more ADH
Blood enters brain

16. If body has too little water

17. If body has too much water

18. Decreased water potential of blood
Dehydration
Decreased water potential of blood
Osmoreceptors cells in hypothalamus lose water (so shrink)
Stimulates nerve cells in the hypothalamus
Increased ADH (antidiuretic hormone) production by posterior pituitary gland
ADH carried in the blood
ADH arrives at the collecting duct

19. ADH causes the cells of the collecting duct wall to become more porous to water, by inserting more aquaporin pores in the cell membrane. More water can then leave via osmosis.

20. Low ψ High ψ From Capillary DCT Collecting Duct Cells
ADH
Active
phosphorylase
enzyme
Water
High ψ
Low ψ
Collecting Duct lumen
Aquaporins

21. If a person is dehydrated, the hormone ADH (antidiuretic hormone) is released.  This causes aquaporin channels to be inserted in the membrane of the collecting ducts (kidneys) so that large quantities of water can be reabsorbed, rather than letting this water be lost in the urine. Small urine volume.

22. If a person is over-hydrated, no ADH (antidiuretic hormone) is released.  This causes aquaporin channels to remain closed in the collecting ducts. Large quantities of water will be removed from the body in the urine. Lots of dilute urine will be made.

24. What about the effect of caffeine?
Caffeine is a stimulant drug which acts on the central nervous system.
It decreases the kidney’s ability to reabsorb sodium and water. This can lead to electrolyte and fluid imbalances.
It increases cardiovascular rate… the kidneys must filter a higher volume of blood so may not reabsorb water efficiently.
It is a diuretic… increasing urine production and urination frequency. Dehydration can occur.

25. What effect does alcohol or ecstasy have?
Alcohol can decrease the amount of ADH being produced, resulting in a greater volume of more dilute urine being produced. This can lead to dehydration.
Ecstasy has the opposite effect. It increases the amount of ADH which reduces the amount of urine produced.
Both alcohol and ecstasy interfere with the normal regulation of water in the body and may have harmful long-term effects on the body.

26. Answer the following questions
Alcohol is known as a diuretic; it inhibits ADH production. Explain how drinking alcohol would effect the urine production of someone who had been drinking.
What is negative feedback?
Why is osmoregulation an example of negative feedback?

27. Control of water potential in the blood by negative feedback27

28. Put in correct order!
Vesicles containing water permeable channels move to and fuse with membrane of the cell 1
Presence of ADH detected by receptors in membrane of collecting duct 2
Osmoreceptors detect low water content of body fluids 3
Enzyme active phophorylase produced 4
ADH produced, secreted into capillaries of post pituitary gland 5
Water diffuses down water potential gradient out of collecting duct 6

29. Answers... 3 Osmoreceptors detect low water content of body fluids
ADH produced, secreted into capillaries of post pituitary gland 5
Presence of ADH detected by receptors in membrane of collecting duct 2
Enzyme active phophorylase produced 4
Vesicles containing water permeable channels move to and fuse with membrane of the cell 1
Water diffuses down water potential gradient out of collecting duct 6