Homeostatis

Question 1

How does a healthy kidney produce urine? (5)

Answer 1

1) First filtering the blood.
2) Reabsorbing all the sugars
3) Reabsorbing the dissolved ions needed by the body.
4) Reabsorbing as much water as the body needs.
5) Releasing urea, excess ions and water as urine.

Question 2

How many kidneys does the human body have?
What is the function of kidneys?
Where is urine stored before being removed from the body?

Answer 2

The body has two kidneys.
They filter the blood, excreting substances you do not want and keeping those substances that the body needs.
Urine is stored in the bladder before being removed from the body.

Question 3

What is homeostasis?

What five internal conditions must be controlled in the body?

Answer 3

Homeostasis is the process of controlling internal conditions and keeping them within a narrow range.

1) Temperature
2) Blood sugar level
3) Ion content
4) Water content
5) Level of waste products

Question 4

Give two waste products that have to be removed from the body and explain how they are formed and removed.

Answer 4

1) Carbon dioxide is produced by respiration and is removed via the lungs when we breathe out.
2) Urea is produced by the kidneys from the breakdown of amino acids, it is removed by the kidneys in urine and is temporarily stored in the bladder.

Question 5

How do water and ions enter the body?

What may happen if the water or ion content in the body is wrong?

Answer 5

Water an ions move into the body when we eat and drink, if the water or ion content in the body is wrong, too much water may move into or out of the cells. This could damage or destroy the cells.

Question 6

How can a person be kept alive if they suffer from kidney failure?
What does a dialysis machine do?

Answer 6

If a person suffers from kidney failure, they can be kept alive by dialysis.
A dialysis machine carries out the same job as the kidneys.

Question 7

Explain the process of dialysis. (8)

Answer 7

1) The dialysis machine is connected to a vein in the arm of the patient.
2) Blood flows to the dialysis machine via a pump and blood thinners prevent the blood from clotting.
3) The dialysis membrane is partially permeable.
4) The dialysis fluid contains the same concentration of useful substances that the patient’s blood does.
5) This means that these substances do not diffuse out of the blood so they do no need to be reabsorbed.
6) Urea diffuses out of the blood into the dialysis fluid.
7) The clean blood then leaves the dialysis machine and flows through a bubble trap to get rid of any bubbles.
8) The clean blood is then returned to a vein in the persons arm.

Question 8

Give one positive and one negative of dialysis.

Answer 8

Positive:
Dialysis restores the concentration of substances in the blood back to normal.
Negative:
Dialysis is quite restrictive as it must be carried out at regular intervals.

Question 9

What is a better option than dialysis for most patients?

Answer 9

A kidney transplant is a better option than dialysis for most patients.

Question 10

Where can kidneys for kidney transplants be obtained from?

What must the kidney be a very good tissue match?

Answer 10

Kidneys may be obtained from a victim of a fatal accident or sometimes from living donors.
The transplant kidney must be a tissue match to prevent rejection.

Question 11

What are antigens?
How may the body react to a transplant kidney?
What must the recipient take following a kidney transplant and why?

Answer 11

Antigens are proteins on the surface of cells.
The recipient’s antibodies may attack the antigens on the donor organ because they recognise them as being ‘foreign’.
Following a transplant the recipient must take immunosuppressant drugs to suppress the immune response to prevent rejection.

Question 12

What is the major disadvantage of kidney transplants?

Answer 12

There are some risks from operations and treatment before and following the transplant involves suppressing the patients immune system, which leaves them vulnerable to common infections.

Question 13

At what temperature must the human body be kept and why?

What must be kept stable?

Answer 13

Human body temperature must be ket at 37ºC so that enzymes will work properly.
The core temperature deep inside the body must be kept stable.

Question 14

What is body temperature monitored and controlled by?

How does this centre do this?

Answer 14

The body temperature is monitored and controlled by the thermoregulatory system in the brain. The centre has receptors which detect the temperature of blood flowing through the brain. Temperature receptors in the skin also send impulses to the brain to give information about skin temperature.

Question 15

What two things happen in the body if the core temperature rises and why?

Answer 15

If the core temperature rises:

1) Blood vessels near the surface of the skin dilate allowing more blood to flow through the skin capillaries, energy is transferred by radiation and the skin cools.
2) Sweat glands produce more sweat. Water evaporates from the skin’s surface, the energy required for the water to evaporate comes from the skin’s surface, so we cool down.

Question 16

What two things happen in the body if the core temperature falls and why?

Answer 16

If the core temperature falls:

1) Blood vessels near the surface of the skin constrict and less blood flows through the skin capillaries, less energy is radiated which prevents heat loss.
2) We shiver, i.e. muscles contract quickly, this requires respiration and some of the energy released warms the blood.

Question 17

When deciding on the best course of treatment for a patient who has suffered kidney failure, what must doctors consider? (5)

Answer 17

1) The general health of the patient.
2) How long the patient has been on dialysis.
3) Cost of treatment - long term cost of dialysis against the cost of an expensive operation followed by treatment with immunosuppressant drugs.
4) The risks of a transplant operation, e.g. infection or risks associated with anaesthetics.
5) The availability of donor kidneys.

Question 18

What three ethical issues should be considered when deciding the right course of treatment for a patient with kidney failure?

Answer 18

1) Should everyone be automatically on a transplant register, or should they ‘opt’ in.
2) Should people be paid to be donors?
3) Should people pay for a new kidney to jump the queue.

Question 19

What are the benefits of carrying a donor card?

Answer 19

Carrying a donor card means families do not have to make a distressing decision about organ donation immediately after the death of a close relative.

Question 20

What are the negatives of small children having a large surface area to volume ratio?

Answer 20

They transfer energy to the surroundings very quickly in cold conditions and dehydrate very quickly in hot conditions.

Question 21

What can be the impact of low temperature in a child?

What can be the impact of dehydration in a child?

Answer 21

If the body temperature is too low the respiratory enzymes work too slowly and too little energy is released.
If the child dehydrates they cannot cool down, so they overheat, which means enzymes denature.

Question 22

Which organ in the body monitors and controls the level of glucose in the body?
What does it do if there is too much glucose in our blood?

Answer 22

The Pancreas.

If there is too much glucose in our blood the pancreas produces the hormone insulin.

Question 23

What does insulin do?

What happens to excess glucose in the liver?

Answer 23

Insulin causes the glucose from the blood to move into cells and the blood glucose level to fall.
In the liver excess glucose is converted to glycogen for storage.

Question 24

What happens if the level of blood sugar gets too low? (4)

Answer 24

1) If the level gets too low, receptors in the pancreas detect the low level.
2) The pancreas releases glucagon, another hormone.
3) The glucagon causes the glycogen in the liver to change into glucose.
4) This glucose is released back into the blood.

Question 25

What is type 1 diabetes?

How is type1 diabetes controlled?

Answer 25

Type 1 diabetes is a condition where the pancreas produces little or no insulin and the blood sugar level may become very high.
It is controlled by careful attention to diet and levels of exercise and injections of insulin.

Question 26

What new methods are scientists and doctors trying to develop to treat and cure type 1 diabetes? (5)

Answer 26

1) Pancreas transplants
2) Transplanting pancreas cells
3) Using embryonic stem cells to produce insulin secreting cells.
4) Using adult stem cells from diabetic patients
5) Genetically engineering pancreas cells to make them work properly.

Question 27

What is Type 1 diabetes traditionally treated with and how is it produced?
How often do diabetics have to inject insulin?

Answer 27

Type 1 diabetes is traditionally treated with human insulin produced by genetically engineered bacteria.
The diabetic has to inject before meals every day of their life.

Question 28

How do some diabetics get insulin into their body, what is the advantage of this?

Answer 28

Some diabetics use pumps attached to the body. They can adjust the level of insulin injected by the pump.

Question 29

What is different about the amount of insulin active diabetics have to inject into their body?

Answer 29

They have to match the amount of insulin injected with their diet and exercise.