1. Learning Intentions
I can explain the process of homeostasis in the control of blood water concentration if it varies from the norm.
I understand the importance of water control and what happens to the body if control is not maintained.
I can give a detailed explanation of how ADH affects the kidneys in response to low blood water concentration.
Success Criteria
I can describe the role of the hypothalamus and pituitary gland in the hormonal control of blood water concentration.
I can give detail of how ADH affects the kidney tubules.

2. Our bodies gain water in 3 different ways:
Drinking water
Eating foods
Chemical reactions – e.g. respiration

3. Our bodies lose water in 4 different ways:
Urine
Faeces (moist faeces are expelled more easily)
Breathing out
Sweating (evaporation of water keeps the body cool)

4. Water Gain = Water Loss Water Balance
Our kidneys ensure that the water concentration of our bodies always stays the same:
Water Gain = Water Loss

6. Water Regulation
The kidneys regulate water, but this is controlled by the brain.
The brain produces ANTI-DIURETIC HORMONE (A.D.H.) which controls the volume of water reabsorbed by the kidney nephrons.
Different volumes of ADH are produced to suit the varying water conditions of the body, ensuring water balance is maintained.
Use worksheet C1 and the following statements.
“Drinking”
“Brain produces more ADH”
“Water content in blood low”
“Low volume of water reabsorption by kidney”
“Low volume of concentrated urine”
“High volume of dilute urine”

7. Bowman’s Capsule
ADH control
Animation

8. Role of ADH Water content of blood too low
Water content of blood too high
Salt eaten or much sweating
Too much water drunk
Water content of blood normal
Brain releases little ADH
Brain releases a lot of ADH
High volume of water passes into blood
Low volume of water passes into blood
High volume of water reabsorbed by kidney
Low volume of water reabsorbed by kidney
Small volume of concentrated urine passed to the bladder
High volume of dilute urine passed to the bladder

9. High Water Conc. In Blood
Less ADH released from brain
Less water reabsorbed from the nephron into the blood
High quantity of dilute urine produced
Water conc. of blood returns to normal

10. Low Water Conc. In Blood Lots of ADH released from the brain.
Lots of water reabsorbed from the nephron into the blood.
Low volume of concentrated urine is produced
Water conc. of the blood returns to normal