Learning IntentionsI 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 CriteriaI 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.

• Our bodies gain water in 3 different ways:Our bodies gain water in 3 different ways:

• Drinking waterDrinking water

• Eating foodsEating foods

• Chemical reactions – e.g. respirationChemical reactions – e.g. respiration

• Our bodies lose water in 4 different ways:Our bodies lose water in 4 different ways:

• UrineUrine

• Faeces (moist faeces are expelled more Faeces (moist faeces are expelled more easily)easily)

• Breathing outBreathing out

• Sweating (evaporation of water keeps the Sweating (evaporation of water keeps the body cool)body cool)

Water BalanceWater Balance

• Our kidneys ensure that the water Our kidneys ensure that the water concentration of our bodies always stays concentration of our bodies always stays the same:the same:

Water Gain = Water LossWater Gain = Water Loss

Water RegulationWater Regulation• The kidneys regulate water, but this is controlled The kidneys regulate water, but this is controlled

by the brain.by the brain.

• The brain produces The brain produces ANTI-DIURETIC ANTI-DIURETIC HORMONEHORMONE (A.D.H.) (A.D.H.) which controls the volume which controls the volume of water reabsorbed by the kidney nephrons.of water reabsorbed by the kidney nephrons.

• Different volumes of ADH are produced to suit Different volumes of ADH are produced to suit the varying water conditions of the body, the varying water conditions of the body, ensuring water balance is maintained.ensuring water balance is maintained.

Bowman’s Capsule

ADH controlAnimation

Water content of blood normal

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

Water content of blood too low

Water content of blood too high

Salt eaten or much sweating

Too much water drunk

Role of ADHRole of ADH

Small volume of concentrated urine passed to the bladder

High volume of dilute urine passed to the bladder

Brain releases a lot of ADH

Brain releases little ADH

High WaterHigh Water Conc. In Blood Conc. In Blood

• Less ADHLess ADH released from brain released from brain

• Less waterLess water reabsorbed from the nephron reabsorbed from the nephron into the bloodinto the blood

• High quantityHigh quantity of of dilute urinedilute urine produced produced

• Water conc. of blood returns to normalWater conc. of blood returns to normal

Low WaterLow Water Conc. In Blood Conc. In Blood

• Lots of ADHLots of ADH released from the brain. released from the brain.

• Lots of waterLots of water reabsorbed from the nephron reabsorbed from the nephron into the blood.into the blood.

• Low volumeLow volume of of concentrated urineconcentrated urine is is producedproduced

• Water conc. of the blood returns to normalWater conc. of the blood returns to normal