Osmoregulation is the process by which the body controls water concentration and salt levels in the blood and body tissues. The hypothalamus contains osmoreceptors that detect changes in blood water concentration. When the concentration decreases, the pituitary gland releases antidiuretic hormone (ADH) which signals the kidneys to reabsorb more water from urine and reduce water loss. This helps regulate water levels and maintain homeostasis.

5. low water intake

6. eating salty food

7. breathing dry air

8. caffeine and alcohol

10. Detecting a change If blood water concentration changes from the ‘norm’ specialised cells (osmoreceptors) in the hypothalamus gland in the brain detect this change

11. Blood water levels The volume of water in our blood also needs to be adjusted to ensure blood does not become too ‘thick’ or too dilute Our blood water levels are checked & corrected by negative feedback to ensure we have the correct level of water in the blood

12. Osmoregulation means the way the body controls water concentration (and consequently salts and ions) The hypothalamus in the brain contains the osmoreceptors ADH (produced by the pituitary gland) increases the volume of water reabsorbed from glomerular filtrate in the kidney

13. Control of blood water levels & the kidney Water concentration in the blood may decrease if a person ______, does not _____ or consumes _____ foods

14. Revision: the kidneys are responsible for controlling water concentration though the action of __ __ __ More __ __ __ means _____ water is reabsorbed by the cells around the tubule Less __ __ __ means _____ water is reabsorbed by the cells around the tubule

15. Little ADH produced MESSAGE PITUITARY Kidney tubules and ducts become LESS permeable Corrective response brings about NEGATIVE FEEDBACK CONTROL OSMORECEPTORS IN HYPOTHALAMUS Less water reabsorbed into blood, large volume of dilute urine produced RECEPTORS EFFECTORS INCREASE IN WATER CONC OF BLOOD NORMAL (SETPOINT) NORMAL (SETPOINT) Osmoregulation MORE water reabsorbed into blood, small volume of concentrated urine produced Corrective response brings about NEGATIVE FEEDBACK CONTROL OSMORECEPTORS IN HYPOTHALAMUS DECREASE IN WATER CONC OF BLOOD RECEPTORS Kidney tubules and ducts become MORE permeable EFFECTORS PITUITARY Much ADH produced MESSAGE

16. Little ADH produced MESSAGE PITUITARY Kidney tubules and ducts become LESS permeable Corrective response brings about NEGATIVE FEEDBACK CONTROL OSMORECEPTORS IN HYPOTHALAMUS Less water reabsorbed into blood, large volume of dilute urine produced RECEPTORS EFFECTORS INCREASE IN WATER CONC OF BLOOD NORMAL (SETPOINT) NORMAL (SETPOINT) Osmoregulation Corrective response brings about NEGATIVE FEEDBACK CONTROL MORE water reabsorbed into blood, small volume of concentrated urine produced DECREASE IN WATER CONC OF BLOOD RECEPTORS OSMORECEPTORS IN HYPOTHALAMUS Kidney tubules and ducts become MORE permeable EFFECTORS PITUITARY Much ADH produced MESSAGE

17. Little ADH produced MESSAGE PITUITARY Kidney tubules and ducts become LESS permeable Corrective response brings about NEGATIVE FEEDBACK CONTROL OSMORECEPTORS IN HYPOTHALAMUS Less water reabsorbed into blood, large volume of dilute urine produced RECEPTORS EFFECTORS INCREASE IN WATER CONC OF BLOOD NORMAL (SETPOINT) NORMAL (SETPOINT) Osmoregulation Corrective response brings about NEGATIVE FEEDBACK CONTROL MORE water reabsorbed into blood, small volume of concentrated urine produced OSMORECEPTORS IN HYPOTHALAMUS DECREASE IN WATER CONC OF BLOOD RECEPTORS Kidney tubules and ducts become MORE permeable EFFECTORS PITUITARY Much ADH produced MESSAGE

18. Affect of ADH

19. True or False ADH is produced by the thyroid gland

20. True or False ADH is produced when we are thirsty

21. True or False ADH causes kidney tubules to reabsorb more water

22. True or False ADH has the effect of decreasing the volume of urine produced

23. The Leah Betts Story Leah Betts died after taking an ecstacy tablet The ecstacy caused lots of ADH to be released How would this affect urine production?

24. Lots of ADH prevents production of lots of dilute urine This then caused a build up of water inside body cells especially the brain Brain cells soak up fluid causing them to swell This caused the brain to be crushed against the inside of the skull Brain damage Coma Death

25. Leah Betts Story

26. Osmoregulation What is the general name for a cell or organ that detects changes in the internal environment?

27. Osmoregulation Where are these cells located in animals?

28. Osmoregulation What is the general name for a cell or organ that carries out a corrective mechanism to return a change in the internal environment back to normal?

29. Osmoregulation What is the name of this organ in animals?

30. Osmoregulation Hormones are chemical messengers that travel in the bloodstream. What is the name of the hormone that targets the kidney tubules? 2. What effect does ADH have on the kidney tubules if: a. The water concentration of the blood is high. b. The water concentration of the blood is low.

31. Answers Hormones are chemical messengers that travel in the bloodstream. What is the name of the hormone that targets the kidney tubules? ANTI DIURETIC HORMONE (ADH) 2. What effect does ADH have on the kidney tubules if: a. The water concentration of the blood is high. LESS ADH = LESS PERMEABLE b. The water concentration of the blood is low. MORE ADH = MORE PERMEABLE

32. Your tasks… Must complete… Copy fig33.4: homeostatic control of blood water conc. (page 308) Should complete… Answer in full sentences: (1) Where are osmoreceptors found? (2) Outline how negative feedback controls water conc. of the blood Compare the volume and the concentration of urine produced if (a) a lot of ADH is present in the blood (b) a little ADH is present in the blood Could complete… Practice past paper questions