1. Coordination and Control L3: Homeostasis
Learning Objectives:
Describe why the body needs to maintain constant level of water, level ions, and temperature in the body.
Explain how organs in the body maintain homeostasis.
Analyse the effect of different changes on the human body.

2. Homeostasis
Homeostasis = the human body’s maintenance of a constant internal environment
This is how the body keeps the conditions inside the body the same.
We are going to study how the body regulates
Water levels
Ion levels
Glucose levels
Internal temperature

3. Water The human body needs water for a variety of reasons:
Allows chemical reactions to happen inside cells
Fills cells to hold their shape
Regulate temperature
Keeps tissues moist
Digestion
Excretion of waste

4. Why is it important to have constant water levels?
Water can move into and out of cells.
Too much water moving into cells at once can cause cells to burst.
Too little water moving into cells can cause cells to become dehydrated.

6. Losing Water What processes causes the body to lose water? Sweating
Breathing out
Urination (removing waste)
You replenish lost water through food and drink.

7. Regulation of Water
The kidneys control how much water is lost through urination.
If water levels are high, more water is removed from the bloodstream and added to urine.
If water levels are low, less water is removed from the bloodstream to be added to urine.

8. Ions Mineral ions are needed for a variety of reasons.
One reason salt is needed is to help regulate water levels.
Salt (sodium chloride) is also necessary for the proper function of muscles and nerves (provides sodium ions).

9. Losing Ions What processes causes the body to lose ions? Sweating
Breathing out
Urination (removing waste)
You replenish lost ions through food and drink.

10. Regulation of Ions
Kidneys also control the amount of ions removed in urine.

11. Glucose + Oxygen  Carbon Dioxide + Water
Cells need glucose to get energy through respiration.
Glucose + Oxygen  Carbon Dioxide + Water
You get glucose through the digestion of food.
The more energy you use up, the more glucose your cells need.

12. Regulation of Glucose
After digestion, glucose is absorbed into the blood stream.
If blood glucose levels are high, the pancreas produces a hormone (insulin) to lower the blood sugar levels.
If blood glucose levels are low, the pancreas produces different hormone (glucagon) the increases the blood sugar levels.

13. Diabetes Diabetics are unable to regulate blood sugar levels.
Type 1 – the pancreas is unable to produce insulin
Type 2 – the body does not recognise insulin produced

14. Temperature
It is important that the human internal temperature remains at 37o C.
This is because this is the optimum temperature for enzymes to function.
To low temperatures and the chemical reactions would be too slow.
To high temperatures and the enzymes would be destroyed.

15. Regulating Temperature
Your skin is the main organ that regulates body temperature.
If you become too hot, sweating allows you to cool down.
If you become too cold, shivering helps you to warm up.