Homeostasis - Chapter 12

Question 1

What are thermoreceptors?

Answer 1

There are thermoreceptors in the skin that send impulses to the thermoregulatory centre (in the hypothalamus)
These can detect a change of 0.5degrees celcius

Question 2

What happens when core body temp. begins to rise?

Answer 2

When your core body temperature begins to rise:
1. impulses are sent from hypothalamus-body
2. vasodilation - blood vessels that supp;y the surface skin capillaries dilate (open wide) –> lets more blood flow through them
3. Skin warms, so more energy is transferred by radiation to the surroundings, cooling the body
4. Sweat glands produce more sweat - energy is used to evaporate this off. In humid conditions, when it can’t evaporate it is hard to cool off.
5. Water and mineral ion loss must be balanced by food and water

Question 3

When your core body temperature begins to fall?

Answer 3

1. Impulses are sent from the hypothalamus to the body
2. Vasocontriction occurs, where the blood vessels contrict and let less blood flow through them. This prevents the loss of energy, through the skin.
3. Shivering occurs - Muscles contract faster, to generate heat in the body.
4. Sweat glands produce less sweat, to reduce energy loss, from the water evaporating.
5. Hairs on arms begin to rise up, to form an insulating layer around the body

Question 4

What is urea?

Answer 4

the breakdown product of excess amino acids (deamination)
Urea can greatly damage cells if it accumulates as it is toxic

Question 5

How is urea removed?

Answer 5

1. It is passed from the liver cells to the blood
2. In the kidneys it is filtered from the blood
3. Passed out of the boody in urine along with any excess water and salts

Question 6

How is CO2 excreted from the body?

Answer 6

Produced as a waste product in respiration - absorbed by the blood - diffuses into the alveoli - It is then exhaled.

Question 7

Function of kidneys:

Answer 7

1. Carries out selective reabsorption, to reabsorb substances, such as glucose.
2. Regulates the water content in the blood
3. They excrete the toxic waste-products, formed by metabolic reactions.

Question 8

What sort of substances remain in the blood, and are not absorbed by the kidney, during selective reabsorbtion?

Answer 8

Blood cells and large molecules like proteins are too big to leave the blood in the filtering process

Question 9

What has occurred if proteins are present in the urine we produce?

Answer 9

Sign of kidney failure, where kidneys cannot control what they absorb and don’t.

Question 10

What happens after urine is produced in the kidneys?

Answer 10

When urine is produced in the kidneys is trickles into the bladder–> when full you feel the urge to pee
All of glucose is reabsorbed back into the blood - via diffusion AND active transport

Question 11

What is selective reabsorption?

Answer 11

The amount of water and mineral ions that are taken back into the blood (reabsorbed) varies

Question 12

What detects concentration of solutes in the plasma?

Answer 12

Osmoreceptors in the brain detect concentration of solutes in the plasma

Question 13

What is ADH?

Answer 13

• Anti-diuretic hormone
• Helps regulate the amount of water in your body. It works to control the amount of water your kidneys reabsorb as they filter out waste from your blood.

Question 14

What happens when blood becomes too concentrated?

Answer 14

If blood becomes too concentrated: low water levels –> more ADH is secreted by the pituitary gland –>
Causes more reabsorption of water into the blood–> so blood becomes less concentrated –> this produces low volume but concentrated urine.

Question 15

What happens when blood becomes too dilute?

Answer 15

If blood becomes too dilute: high water levels –> less ADH is secreted by the pituitary gland –> Causes less reabsorption of water into the blood –> so blood becomes more concentrated –> this produces high volume but diluted urine.

Question 16

What can damage kidneys, and their effect?

Answer 16

Infections, genes or accidents can damage the kidneys, affecting their ability to filter the blood
Failed kidneys means a build of toxic substances and water levels and mineral ion levels will not be balanced –> this means concentrations will be affected –> cells get damaged by osmosis (they can burst, which is called cell lysis)

Question 17

What can treat kidney failure?

Answer 17

1. Kidney transplant
2. Dialysis

Question 18

What happens in dialysis?

Answer 18

In dialysis, a person’s blood leaves their body and flows between partially permeable membranes (in a machine), where one side is the blood, and the other side is dialysis fluid
Dialysis fluid has the same concentration of useful substances as a healthy person’s blood
Dialysis fluid contains the same concentration of glucose and mineral ions as a normal person - this ensures that there is no net movement of these useful substances OUT of the blood
Dialysis must be repeated at regular intervals

Question 19

Advantages of dialysis:

Answer 19

1. A temporary solution, for when you are waiting for a transplant

Question 20

Disadvantages of dialysis:

Answer 20

1. Very time consuming
2. A careful diet has to be maintained, in order to keep stable blood chemistry for as long as possible

Question 21

What happens in a kidney transplant?

Answer 21

In kidney transplant, the donor kidney is joined to the blood vessels in the groin of the patient

Question 22

Why cannot everyone donate someone their kidney?

Answer 22

Antigens on the donor kidney will be different to the patient’s. So if the donor’s and patient’s kidneys don’t match
The risk with this: the patient’s immune system’s antibodies will attack the antigens on the donor organ –> results in the rejection and destruction of the donated kidney

Question 23

How is the risk of rejection reduced?

Answer 23

1. match the donor organ with a similar tissue type to the patient
2. the patient is given immunosuppressants for the rest of their lives

Question 24

Disadvantages of immunosuppressants?

Answer 24

They stop the patient from being able to deal with any pathogens- even something like the common cold can be fatal.

Question 25

How long can a kidney transplant last and what happens after?

Answer 25

Average kidney transplant lasts around 9 years - they return to dialysis while they wait for a new kidney

Question 26

Disadvantage of long term dialysis?

Answer 26

Long term dialysis is much more expensive than transplant and causes serious damage to the body

Question 27

Advantages of dialysis:

Answer 27

1. Quick solution for kidney failure
2. Keeps you alive while you wait for a kidney transplant

Question 28

Disadvantages of dialysis:

Answer 28

1. More expensive than kidney transplant in the long term.
2. Not a permanent solution for kidney failure
3. Very time-consuming

Question 29

Advantages of kidney transplant:

Answer 29

1. Longer lasting - lasts around 9 years
2. Less time consuming
3. Relatively permanent solution for kidney failure
4. Less expensive in the long term.

Question 30

Disadvantages of Kidney Transplant:

Answer 30

1. Not many donors available.
2. Chances of donor kidney being rejected by the body, so immunosuppressants must be taken. These weaken the immune system, so in the case of disease or pathogens, immune system can not effectively fight these off.

Question 31

Who is commonly recommended for kidney transplant

Answer 31

Family members