Topic 12 Homestatis

Question 1

Define homeostasis

Answer 1

the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.

Question 2

Autonomic control systems may involve

All chemical responses include a

Answer 2

nervous responses or chemical responses.

negative feedback mechanism.

Question 3

Glucose does what

Answer 3

releases energy during respiration)

Question 4

Pancreas does what

Answer 4

the gland which releases insulin and glucagon

Question 5

Insulin does what

Answer 5

(the hormone that stimulates the liver and muscle cells to store excess glucose as glycogen

Question 6

Glucagon does what

Answer 6

(the hormone that stimulates the liver to break down glycogen to release glucose)

Question 7

Glycogen is a

Answer 7

(the large polymer of stored glucose)

Question 8

Liver is the target organ for

Answer 8

(the target organ for insulin and glucagon)

Question 9

If blood glucose is too high what happens?

Answer 9

the pancreas produces the hormone insulin that causes glucose to move from the blood into the cells. In liver and muscle cells, excess glucose is converted to glycogen for storage.

Question 10

If blood glucose is too low, then what happens?

Answer 10

the pancreas produces the hormone glucagon that causes glycogen to be converted into glucose and released into the blood.

Question 11

Discuss the differences between type I and type II diabetes

Answer 11

Type 1: Pancreas does not produce any / enough insulin. Characterised by uncontrolled high blood glucose levels. Treated with insulin injections. Usually early onset.
Type 2: Liver does not respond to insulin. Treated by balancing carbohydrate intake with exercise. Usually develops later. Obesity, diets high in sugar and lifestyles lacking exercise are risk factors.

Question 12

The skin contains temperature receptors and sends

Answer 12

nervous impulses to the thermoregulatory centre.

Question 13

If body temperature is too high, mechanisms are used to increase transfer of energy to the environment:

Answer 13

Vasodilation of arterioles; more blood can flow to the skin’s surface
Sweat production from sweat glands; sweat evaporates from the skin

Question 14

Describe control of blood glucose concentration

Answer 14

1. Eating foods containing carbohydrate puts glucose (a type of sugar) into the blood from the gut
2. The normal metabolism of cells removes glucose from the blood
3. Vigorous exercise removes much more glucose from the blood
4. Excess glucose can be stored as glycogen in the liver and in the muscles
5. The level of glucose in the blood must be kept steady. Changes are monitored and controlled by the pancreas, using the hormones insulin and glucagon, in a negative feedback cycle.

Question 15

State that uncontrolled water loss occurs via the ——– during exhalation and via the ——— during sweat ( along with ——– and ———–)

Answer 15

lungs
skin
ions
urea

Question 16

Describe production of urea:

Answer 16

The digestion of proteins from the diet results in excess amino acids
Excess amino acids are deaminated in the liver to form ammonia.
Ammonia is toxic so is converted to urea for safe excretion.

Question 17

The kidneys produce urine by

Answer 17

by filtration of the blood and selective reabsorption of useful substances (glucose, some ions and some water).

Question 18

Describe the effect of ADH on the permeability of the kidney tubules

Answer 18

ADH is released by the pituitary gland when the blood is too concentrated
More water is reabsorbed back into the blood from the kidney tubules
This is controlled by negative feedback

Question 19

Describe how kidney failure can be treated by kidney dialysis.
Describe the basic principles of how kidney dialysis works.
Evaluate the advantages and disadvantages of treating organ failure by mechanical device

Answer 19

1. Dialysis has to be done regulary to keep the concentrations of dissolved substances in the blood at normal levels, and to remove waste substances
2. In a dialysis machine the person’s blood flows between the partially permeable membranes, surrounded by dialysis fluid. The membranes are permeable to things like ions and waste substances, but not big molecules like proteins (just like the membranes in the kidney).
3. The dialysis fluid has the same concentration of dissolved ions and glucose as healthy blood
4. This means that useful dissolved ions and glucose won’t be lost from the blood ruing dialysis
5. Only waste substances (such as urea) and excess ions and water diffuse across the barrier
6. Many patients with kidney failure have to have a dialysis session three times a week. Each session takes 3-4 hours- not much fun
7. Plus, dialysis may cause blood clots or infections
8. Being on a dialysis machine is not a pleasant experience and it is expensive from the NHS to run.
9. However, dialysis can buy a patient with kidney failure valuable time until a donor organ is found.

Question 20

Describe how kidney failure can be treated by kidney transplant
Describe the basic principles of how kidney transplant works.
Evaluate the advantages and disadvantages of treating organ failure by transplant.

Answer 20

1. At the moment the only cure for kidney failure is transplant
2. Healthy kidneys are usually transplanted from someone who died suddenly
3. The person who has died has to be on the organ donor register or carry a donor card (provided their relatives agree too).
4. Kidneys can also be transplanted from people who are still alive (as we all have two of them) but there is a small risk to the person donating the kidney
5. There is also a risk that the donor kidney could be rejected by the patient’s immune system. Patients are treated with drugs to prevent this but it can still happen
6. Transplants are cheaper (in the long run) than dialysis and they can put an end to the hours patients have to spend on dialysis but there are longer waiting lists for kidneys

Question 21

If body temperature is too low:

Answer 21

Vasoconstriction - arterioles constrict
so less blood flows to the skin’s surface Sweating stops Skeletal muscles contract (shiver) - transfers energy to the body from glucose through increased respiration.