1. Homeostasis
Noadswood Science, 2016

2. Saturday, June 16, 2018
Homeostasis
To describe homeostasis

3. Precise Learning
Students should be able to explain that homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
Homeostasis maintains optimal conditions for enzyme action and all cell functions.
In the human body, these include control of:
blood glucose concentration
body temperature
water levels

4. Homeostasis
It is important that the internal environment of the body is controlled
Maintaining a constant internal environment is called homeostasis
The nervous system and hormones are responsible for this – some of the internal conditions which are controlled include: -
Water regulation
Ions
Temperature
Blood glucose levels

5. Water Regulation
This is controlled to protect cells by avoiding too much water entering or leaving them
Water content is controlled by water loss from: -
The lungs when we exhale
The skin by sweating
The body, in urine produced by the kidneys

6. Water Regulation
Water enters the body through food and drink as well as being a product of aerobic respiration in cells
If the amount of water in the body is wrong, cells can be damaged because too much water enters or leaves them

7. Ions
Ion (salts) content of the body is controlled to protect cells by avoiding too much water entering or leaving them
Water and ions enter the body when you eat / drink
The water and ion content of the body must be carefully controlled to prevent damage to the cells
Water is lost through breathing, sweating and in the urine
Ions are lost through sweating and urine
If the water or ion content of the body is wrong too much water may move in / out of the cells, as well as the importance of water to help control core temperature and the sugar levels within the blood

8. Urine
Inside the kidneys are millions of nephrons which squeeze all the water out under high pressure
They then reabsorb only as much water as we need, with the rest going to the bladder (removed as urine)

9. Temperature
This is controlled to maintain the temperature at which enzymes work best
Body temperature is controlled by: -
Controlling blood flow to the skin
Sweating
Shivering

10. Temperature
Too hot: -
Sweat glands in the skin release more sweat which evaporates, removing heat energy from the skin
Blood vessels leading to the skin capillaries dilate and become wider allowing more blood to flow through the skin, and more heat to be lost
Too cold: -
Muscles contract rapidly (shiver), which require energy (from respiration) with some of this energy released as heat
Blood vessels leading to the skin capillaries constrict and become narrower letting less blood flow through the skin and conserving heat in the body

11. Temperature Skin capillaries and hairs help regulate temperature…
The hairs on the skin also help to control body temperature – they lie flat when we are warm, and rise when we are cold
The hairs trap a layer of air above the skin, which helps to insulate the skin against heat loss

12. Blood Sugar
This is controlled to provide cells with a constant supply of energy
Blood sugar level is controlled by the release and storage of glucose controlled by insulin
Blood sugar levels are controlled to provide cells with a constant supply of energy
Blood sugar level is controlled by the release and storage of glucose controlled by insulin

13. Insulin
Insulin is a hormone which regulates the amount of sugar in the blood – it converts glucose into glycogen (which can be stored in the liver)
Insulin is produced in the Islets of Langerhans within the pancreas

14. Insulin Insulin controls blood sugar levels: -
Eating carbohydrates puts a large amount of glucose into the blood
Normal metabolism of cells removes glucose from the blood
Vigorous exercise removes much more glucose from the blood
It is vital to control the level of blood glucose – the bodies mechanism for adding or removing glucose is via insulin

15. Insulin
The pancreas monitors and controls the glucose concentration within the blood
The pancreas produced insulin (a hormone) which causes glucose to move from the blood into the cells – lowering the blood [glucose] if it becomes too high
Blood [glucose] can become too high after a meal rich in carbohydrates (sweets; potatoes; bread; rice; pasta etc…)

16. Insulin
Blood [Glucose] Too High – Insulin Added

17. *Glucagon causes the liver to release glucose into the blood
Insulin
Blood [Glucose] Too Low – Insulin Not Added
*When blood sugar is too low another hormone glucagon is released (instead of insulin)
*Glucagon causes the liver to release glucose into the blood

18. Blood Sugar Test Add 2cm3 of each urine sample to a test tube
Test each sample using a clinistix
Compare the colour change to the chart
Which samples contain glucose?
Which are likely to be from a diabetic person?
Why is it important to make sure the test tubes are clean?

19. Blood Sugar Test
Samples which contain glucose will change colour with the clinistix
A diabetic is likely to have glucose in their urine – glucose is essential for the body but excess glucose is a danger for people with diabetes because the ability of the kidneys to absorb glucose is also exceeded, so the excess is excreted in urine. If this glucose is then used up the body will not have enough glucose, which can result in convulsions /coma
It is vital to keep the test tubes clean to stop cross-contamination of the samples

20. Practice Questions Define homeostasis
Give two examples of conditions in your internal environment that need regulating and maintaining

21. Answers
Define homeostasis – the regulation of the conditions inside your body (and cells) to maintain a stable internal environment, in response to changes in both internal and external conditions
Give two examples of conditions in your internal environment that need regulating and maintaining – temperature, blood glucose content, water content etc…