1. Homeostasis

2. Keeping things steady...
Many chemical reactions happen inside your body.
Reactions are controlled by enzymes.
Enzymes work best in certain conditions.
Therefore it is important to keep certain things in our body constant:
Temperature pH
Water content
Many chemical reactions are happening inside your body all the time. Molecules are built up and broken down in your cells. Can you remember what controls these reactions? A slight change in the conditions can slow down or stop the enzyme from working. It is important that things like temperature, pH and water content are kept as steady as possible.
The conditions inside the body must be controlled within narrow limits. This is called homeostasis. These conditions include water content, ion content, body temperature and blood glucose concentration.
The thermoregulatory centre is the part of the brain that monitors and controls body temperature. The pancreas meanwhile monitors and controls blood glucose concentration. It produces a hormone called insulin that reduces blood glucose levels. Diabetes is a disease which can be caused by insufficient insulin.

3. Controlling conditions
Homeostasis – keeping a constant internal environment (controlling conditions in the body within narrow limits)
These conditions include:
Water content
Ion content
Body temperature
Blood glucose concentration
The conditions inside the body must be controlled within narrow limitsThis is called homeostasis. These conditions include water content, ion content, body temperature and blood glucose concentration

4. Controlling conditions
The brain has overall control of our body processes.
When blood flows through the brain, it checks:
the temperature
the concentration of chemicals such as carbon dioxide.
Our blood is providing feedback to our brain.

5. Brain switches on cooling mechanisms
Blood gets too hot
Brain switches on cooling mechanisms
Blood temperature falls
Normal body temp.
Normal body temp.
So what happens if the temperature of the blood reaching the brain is too high? It sends out messages along nerves to parts of the body that lower our temperature e.g. We start to sweat.
If we get too cold the brain detects the blood temperature again. The brain sends messages along nerves to parts of our body that raise our temperature – stop sweating. The control of body temperature is an example of homeostasis. Our blood is providing feedback to our brain.
Brain switches on warming mechanisms
Blood gets too cold
Blood temperature rises

6. Removing waste products
Carbon dioxide
Produced during cellular respiration.
Every cell in body respires.
If it was not removed it would affect the pH of the cells (make it more acidic). This would affect the working of the enzymes in cells.
Carbon dioxide moves out of cells into blood.
Blood carries it back to lungs.
Carbon dioxide removed when you breathe out.
No matter what you are doing, even when you are sleeping, the cells of your body are constantly producing waste products as a result of chemical reactions which are constantly taking place. The more extreme the conditions you put yourself in the more waste products your cells will produce. There are two main poisonous waste products that would cause major problems to your body if levels built up – carbon dioxide and urea.
The air you breathe in contains 0.04% carbon dioxide and the air you breathe out contains 4% carbon dioxide

7. Removing waste products
Urea
Produced in liver when excess amino acids are broken down.
In the liver the amino group is removed and converted into urea. The rest of the amino acid used in respiration or to make other molecules.
Urea (poisonous) passes from liver into blood.
If levels build up in blood causes a lot of damage.
Urea removed from blood by the kidneys. It is then removed in urine.
Urea produced when you eat too much protein, when body tissues are worn out and the extra protein needs to be broken down. Amino acids cannot be used as fuel for your body. Urea removed with any excess water and salt. Urine is produced all the time by the kidneys. It leaves the kidneys and is stored in the bladder, which you empty from time to time.

8. Removing waste products
Water and ions
Water is lost through breathing, sweating and in urine.
Ions are lost in sweat and urine.
If the water or ion content is wrong, too much water may move into or out of your cells.
Water and ion content are carefully controlled to prevent damage to your cells.

9. Controlling body temperature
Where ever you go and whatever you do it is vital that your body temperature is maintained around 37 degrees. This is the temperature at which your enzymes work best. Your skin temperature can vary enormously without causing harm. It is the temperature in deep inside your body (core temp.) which must be kept stable.
At only a few degrees above or below body temperature your enzymes cannot function properly.
All sorts of things can affect your internal temperature including: heat produced by your muscles during exercise, fevers caused by disease, external temperature rising or falling.

10. Temperature regulation
Human enzymes work best at 37ºC, so the body’s temperature is controlled.
A part of the brain called the thermoregulatory centre monitors and controls body temperature.
It gathers information as nerve impulses from temperature receptors in:
the brain - these are sensitive to the temperature of the blood flowing there
the skin - these are sensitive to skin temperature
Thermoregulatory centre contains receptors sensitive to temperature changes – they monitor the temperature of the blood flowing through the brain itself. Extra information comes form the temperature receptors in the skin. These send impulses to the thermoregulatory centre, the receptors are sensitve and can detect a difference as small as 0.5 degrees.

11. Thermoregulatory centre is found in the hypothalamus

13. Temperature regulation
If you become too hot or too cold, there are several ways in which your temperature can be controlled.
Sweating,
Shivering,
Skin capillaries and
Hairs.

14. Too cold When we get too cold:
Muscles contract rapidly - we shiver. These contractions need energy from respiration, and some of this is released as heat.
Blood vessels leading to the skin capillaries become narrower - they constrict - letting less blood flow through the skin and conserving heat in the body.
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.
Blood vessels that supply your skin capillaries.

15. Too hot When we get too hot:
Sweat glands in the skin release more sweat. This evaporates, removing heat energy from the skin.
Blood vessels leading to the skin capillaries become wider - they dilate - allowing more blood to flow through the skin, and more heat to be lost.

16. Too cold
Too hot
A - Hair muscles pull hairs on end.
B - Erect hairs trap air.
C - Blood flow in capillaries decreases.
D - Hair muscles relax. Hairs lie flat so heat can escape.
E - Sweat secreted by sweat glands. Cools skin by evaporation.
F - Blood flow in capillaries increases.
Remember: Capillaries do not move up and down inside the skin. Temperature is regulated by controlling the amount of blood which flows through the capillaries.

17. Controlling blood sugar
The pancreas monitors and controls the concentration of glucose in the blood.
What happens when your blood glucose levels get too high?
Pancreas produces a hormone called insulin.
Insulin causes glucose to move from the blood into cells.
Glucose is changed into glycogen in the liver.
So insulin lowers the blood glucose concentration if it has become too high.
What happens if your blood glucose levels get too low?
Pancreas produces a hormone called glucagon.
Glucagon tells the liver to break the glycogen down to glucose again.
Glucose is released into the blood.
So glucagon raises your blood sugar levels.
It is very important that your cells have a constant supply of glucose because they need it for cellualr respiration. Glucose is transported around the body to all the tissues in your blood
Your body cells need glucose for energy – they need it in controlled amounts. What happens when you eat a high carbohydrate meal? Your blood glucose can go up 20 times but it does not stay high.

18. Insulin causes glucose to change to glycogen
Glucose rises (food intake)
Insulin causes glucose to change to glycogen
Glucose falls
Normal blood glucose level
Normal blood glucose level
Glucagon causes glycogen to change to glucose
Glucose falls (exercise)
Glucose rises

19. Diabetes
Diabetes is a disease where the concentration of glucose in the blood is not controlled properly by the body.
In type 1 diabetes, the pancreas does not produce enough insulin.
This can lead to high levels of glucose in the blood, which can be fatal.
Kidneys produce glucose in urine, produce lots of urine and always thirsty.
Glucose cannot get into cells – lack energy and feel tired.
Break down fat and protein to use as fuel – lose weight.
Diabetes
There are two types of treatment for diabetes:
Careful monitoring of food intake, with particular care taken over carbohydrates - which are digested into glucose.
Injecting insulin into the blood before meals. The extra insulin causes glucose to be taken up by the liver and other tissues. Cells get the glucose they need for respiration, and the blood glucose concentration stays normal.

20. Treating diabetes Type I Type II
Inject insulin into blood (treatment NOT cure).
Type II
Manage diet – avoid carbohydrate rich food.

21. In 2005 scientists produced insulin-secreting cells from stem cells which cured diabetes in mice. More research is needed but the scientists hope that before long diabetes will be a disease that we can cure rather than just treat.