1. Homeostasis We Are Learning Today:
The mechanisms by which the body maintains a constant internal environment
Starter: Sports drinks
Why do runners drink these rather
than just water?
What do the labels claim they can do?
Do you think these claims are true or
are they just a good way for drinks
manufacturers to make quick money?

2. Homeostasis
Humans need to maintain a constant internal environment, controlling levels of water, blood sugar and temperature.
Homeostasis is the result of the coordination of your nervous system, your hormones and your body organs.

3. Thermoregulation: What organs are involved?
Hypothalamus
Muscle

4. Thermoregulation: Controlling temperature
This is controlled to maintain the temperature at
which enzymes work best.
If you get too hot:
Hair muscles relax; hairs lie flat so letting more heat out.
Evaporation of sweat secreted by sweat glands cools skin.
Capillaries dilate, blood flow increases at the surface of the skin causing heat to be lost by radiation.

5. Thermoregulation: Controlling temperature
If you get too cold:
Hairs muscles pull hairs on end, trapping a layer of air which acts as an insulator.
Sweat glands stop secreting sweat.
Capillaries close to surface constrict, to allow less blood to flow.
Muscles shiver, generating heat.

6. Osmoregulation What organs are involved?
Pituitary gland
Hypothalamus
Kidney

7. Osmoregulation: Controlling water
Inputs
Water content in:
Drinking
Digestion
Water made in:
Cellular respiration
Outputs
Water content in:
Urine
Breathing
Sweating
Bowel movement

8. Check your learning
How might you expect the volumes in the above table to change on:
A very hot day
A very cold day

9. Osmoregulation: Controlling water
Place the sequence of events in order:
Detected by the hypothalamus
Kidneys absorb less water from the blood
So less water is lost in urine (urine is more concentrated)
Blood water level returns to normal
Too little water in the blood
More ADH released into the blood by the pituitary gland

10. Too little water in the blood
Detected by the hypothalamus
More ADH released into the blood by the pituitary gland
Kidneys absorb less water from the blood
So less water is lost in urine (urine is more concentrated)
Blood water level returns to normal

11. Glucoregulation – Controlling blood sugar levels
Liver
Pancreas

12. Glucoregulation
It is important that the concentration of glucose in the blood is kept at a constant level.
Glucose is a sugar needed by cells for respiration.
Insulin is secreted by the pancreas to control sugar level.

13. What is insulin?
Insulin is a hormone which affects your metabolism and other body functions.
Insulin causes cells in the liver, muscle, and fat tissue cells to take up glucose from the blood, storing it as glycogen in the liver and muscle, and stopping use of fat as an energy source.
When insulin is absent (or low), glucose is not taken up by body cells, and the body begins to use fat as an energy source.

14. Glucoregulation – Controlling blood sugar levels
Place the sequence of events below in order:
More glucose absorbed by tissues and the liver
Blood glucose reduced
Insulin injected by the pancreas
Blood with too much glucose in it

15. Blood with too much glucose in it
Insulin injected by the pancreas
More glucose absorbed by tissues and the liver
Blood glucose reduced

16. Complete the word loop first to win the prize!
Team Challenge
Complete the word loop first to win the prize!