principles of homeostasis and negative feedback

Question 1

define homeostasis

Answer 1

physiological control system that maintains internal environment within restricted limits

Question 2

describe why homeostasis is important

Answer 2

1. vital for cells to function normally and to prevent from them being damaged
2. vital for controlling enzyme activity which controls the rate of metabolic reactions

Question 3

explain the importance of maintaining a constant core temperature

Answer 3

1. if temperature is too high = enzymes denature because enzyme molecules vibrate too much breaking their hydrogen bonds that maintain their tertiary structure
2. shape of active site is changed so they can no longer act as a catalyst
3. the highest rate of enzyme activity = optimum temperature

Question 4

explain the importance of maintaining a constant blood pH

Answer 4

1. if pH is too high/low = enzymes denature due to the breakage of the hydrogen bonds that hold their tertiary structure
2. shape of active site changes and they can no longer act as a catalyst
3. efficiency of metabolic reactions decreases
4. highest metabolic rate = optimum pH

Question 5

why is it important to maintain the right concentration of glucose in the blood

Answer 5

• because glucose is a respiratory substrate
• needed for respiration that produces the energy (ATP) required by cells

Question 6

what does glucose blood concentration affect

Answer 6

blood water potential

Question 7

explain the effects of having a high blood glucose concentration on water potential

Answer 7

1. water potential of blood decreases
2. water molecules diffuse out of cells into the blood via osmosis
3. cells shrivel up and die

Question 8

explain the effects of having a low blood glucose concentration on water potential

Answer 8

1. glucose is a respiratory substate
2. cells are unable to carry out metabolic reactions because there is not enough energy
3. there is not enough energy because there is not enough glucose for respiration to provide ATP

Question 9

what is the function of negative feedback

Answer 9

to restore systems to their original level

Question 10

outline the process of negative feedback

Answer 10

• receptors detect when levels are too high/low
• information is communicated via nervous/hormonal system to effectors
• effectors counteract change by bringing the level back to optimum

Question 11

when may effectors not be able to counteract change

Answer 11

when the change is too large

Question 12

explain the advantages of having multiple negative feedback systems

Answer 12

• you would have less control and a slower response
• because you’d only be able to actively change a level in one direction so it returns to normal

Question 13

what is the function of positive feedback

Answer 13

amplifies a change from the normal level

Question 14

what is positive feedback useful for?

Answer 14

useful for rapidly activating something

Question 15

when can positive feedback occur

Answer 15

when a homeostatic system breaks down

Question 16

explain why is positive feedback not involved in homeostasis

Answer 16

positive feedback is not involved in homeostasis because it doesn’t keep your internal environment stable