Homeostasis

Question 1

What is the normal human body temperature?

Answer 1

37 degrees Celsius as enzymes work best

Question 2

How does the body react when body temperature gets too high?

Answer 2

1) Sweat glands release sweat onto the surface of the skin. The sweat now evaporates and this takes energy from the body, cooling it down.
2) The blood vessels supplying the capillaries dilate (vasodilation). This means that more blood flows through the capillaries. Heat can now transfer out of the blood. So the body temperature can return to normal.

Question 3

How does the body react when body temperature gets too low?

Answer 3

1) Blood vessels supplying the capillaries constrict (vasoconstriction). Less blood now flows through the capillaries, so less heat is lost from the body.
2) Shivering: skeletal muscles contract. Muscle cells increase the rate of respiration to generate more energy for this. This releases heat which warms the body.
3) Stop sweating

Question 4

Endocrine system compared with the nervous system.

Answer 4

The glands in the endocrine system secrete hormones directly into the bloodstream.
The nervous system uses electrical impulses which travel down neurones.
Endocrine produces a slower and more long lasting effect than the nervous system.

Question 5

What glands does the endocrine system consist of?

Answer 5

Pituitary gland, thyroid, adrenal glands, pancreas, ovaries, testes

Question 6

How does the body react when blood glucose levels get too high?

Answer 6

1) Sensed by the pancreas.
2) So it produces insulin.
3) Insulin travels in the bloodstream all around the body.
4) This triggers body cells to take up glucose from the blood.
5) Triggers liver and muscle cells to store excess glucose as glycogen.
6) So the concentration of glucose in the blood returns to its normal level.

Question 7

How does the body react when blood glucose levels get too low?

Answer 7

1) Pancreas releases glucagon into the bloodstream.
2) Glucagon triggers liver cells to convert glycogen stores back to glucose.
3) Then it is released into the blood.
4) Concentration returns to normal.

Question 8

What is type 1 diabetes?

Answer 8

When the pancreas doesn’t produce enough insulin. Blood glucose level rises and then stays at a high level. They inject themselves with insulin when levels are too high throughout the day, typically after meals. This makes sure glucose gets removed quickly once the food has been digested.

• limit simple carbohydrate intake
• regularly exercise

Question 9

What is type 2 diabetes?

Answer 9

When the body cells stop responding to the insulin produced by the pancreas. This causes glucose levels to get too high. Often treated with a diet with a controlled level of carbohydrates and getting regular exercise. Obesity is a major risk factor for this.

Question 10

How does the body lose water?

Answer 10

Via the lungs when we exhale.
When we sweat we lose water through the skin. (contains sodium ions and urea)
Via the kidneys in urine.

Question 11

What does the kidney do if the water is too dilute?

Answer 11

The kidneys remove the excess water and produce a greater volume of urine. Urea and excess ions are also removed in urine.

Question 12

How do the kidneys remove urea?

Answer 12

1) Blood enters the kidney through an artery- this blood contains the waste product urea.
2) The kidneys remove the urea as well as excess ions and excess water.
3) They leave as urine which is stored in the bladder.
4) The blood now leaves the kidney through a vein, and now it contains no urea.

Question 13

How do the kidneys adjust the level of molecules in the blood?

Answer 13

1) The blood passes through capillaries.
2) Small molecules are filtered out of the blood.
3) These include urea, ions and water and glucose.
4) They pass into a tube. All of the glucose, some ions and some water are reabsorbed into the blood.
5) This is called selective reabsorption.
6) Urea, excess ions, and excess water are released as urine.

Question 14

How does the body deal with excess amino acids?

Answer 14

1. Proteins are long chains of amino acids.
2. When we digest protein, amino acids pass into the blood.
3. The liver breaks down the excess amino acids and produces ammonia.
4. This is called deamination.
5. Ammonia is very toxic so the liver immediately converts it into urea to be safely excreted by the kidneys.

Question 15

How does the body respond to low water content?

Answer 15

Receptor in the brain detects low levels.
The pituitary gland releases ADH into the bloodstream.
ADH travels to the kidneys and causes the kidney tubules to become more permeable to water.
More water is reabsorbed from the tubules back into the blood
Less urine is produced and water content goes back to normal
Release of ADH stops.

Question 16

How does the body react to high water content?

Answer 16

Receptors detect concentration of water in the blood rising.
Pituitary gland stops releasing ADH.
Kidney reabsorbs less water into the blood.
More urine in produced.
Water levels go back to normal.

Question 17

What happens if your kidneys don’t work properly?

Answer 17

You can’t control the levels of ion and water which can result in death.

Question 18

How does kidney dialysis work?

Answer 18

Patient’s blood passes through a partially permeable membrane.
This allows urea, water and ions through.
It will not allow blood cells and larger molecules such as proteins to pass through.
The other side of the membrane has dialysis fluid.
This contains normal concentrations of water and ions and doesn’t contain urea.
The urea diffuses from the blood into the fluid.
The fluid is constantly refreshed which ensures there is always a large concentration gradient for urea.
Some of the water and ions will diffuse from the blood to the dialysis fluid.
Concentrations of these will return to normal for the patient.

Question 19

Explain what gibberellins and ethene do?

Answer 19

Gibberellins are important in initiating seed germination.

Ethene controls cell division and ripening of fruits.