3.4.6 Homeostasis and Negative Feedback

Question 1

What is meant by homeostasis?

Answer 1

Maintenance of a stable internal environment

Question 2

Explain what happens when the body temperature is too high (i.e. to enzymes)

Answer 2

• Enzymes denature
  
  • Enzyme’s molecules vibrate too much = breaks H-bonds holding them in their 3D shape
  • Shape of enzyme’s active site changes = no longer works as catalyst
  • Mean metabolic reactions are less efficient

Question 3

Explain what happens when the body temperature is too low (i.e. to enzymes)

Answer 3

Enzyme activity is reduced = slows rate of metabolic reactions

Question 4

Explain what happens when the pH is too high/low (i.e. to enzymes)

Answer 4

1. H-bonds holding them in their 3D shape break ∴ shape of enzyme’s active site changes & no longer works as catalyst
2. Metabolic reactions are less efficient

Question 5

Explain what happens when the blood glucose levels are too high

Answer 5

• Ψw is reduced to point where water molecules diffuse out cells into blood by osmosis
• Causes cells to shrivel up and die

Question 6

Explain what happens when the blood glucose levels are too low

Answer 6

Cells unable to carry out normal activities ∵ isn’t enough glucose for respiration to provide energy

Question 7

What is negative feedback?

Answer 7

Mechanisms that restore the level to normal (to the set point)

Question 8

Negative feedback only works within certain ___

Answer 8

limits

If change is too big = effectors may not be able to counteract it

Question 9

Homeostasis involves _____ negative feedback mechanisms

Answer 9

multiple

Question 10

Why does homeostasis involve multiple negative feedback mechanisms?

Answer 10

• ∵ gives more control
• & allows you to actively increase or decrease a level so it returns to normal

Question 11

1 negative feedback mechanism means ___ ____ and ___ ____

Answer 11

slower response and less control

Question 12

What does postive feedback do?

Answer 12

Amplifies a change from the normal level

Question 13

What does postive feedback cause effectors to do?

Answer 13

Effectors respond to further increase the level away from normal level

Question 14

What is postive feedback useful for?

Answer 14

Useful to rapidly activate something

e.g. blood clot after injury

Question 15

Positive feedback is ___ involved in homeostasis

Answer 15

NOT

Question 16

When does positive feedback also occur?

Answer 16

When homeostatic system breaks down

e.g. of you’re too cold for too long

Question 17

Hypothermia involves ____ feedback

Answer 17

postive

Question 18

When does hypothermia occur?

Answer 18

Happens when heat’s lost from body quicker than it can be produced

Question 19

As body temp. ↓, brain….

Answer 19

doesn’t work properly & shivering stops

Makes body temp. ↓ even more

Question 20

Describe the role of positive feedback in hypothermia

Answer 20

Positive feedback takes body temperature further away from normal level & continues to decrease unless action is taken