Topic 7.1 - 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 causing H-bonds to holding them in their 3D shape to break
  • Shape of enzyme’s active site changes so it 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 therefore the 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

• Water potential 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 because there 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

Why does homeostasis involve multiple negative feedback mechanisms?

Answer 8

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

Question 9

What does postive feedback do?

Answer 9

Amplifies a change from the normal level

Question 10

What does postive feedback cause effectors to do?

Answer 10

Effectors respond to further increase the level away from normal level

Question 11

What is postive feedback useful for?

Answer 11

Useful to rapidly activate something

e.g. blood clot after injury

Question 12

Positive feedback is ___ involved in homeostasis

Answer 12

NOT

Question 13

When does positive feedback also occur?

Answer 13

When homeostatic system breaks down

e.g. of you’re too cold for too long

Question 14

Hypothermia involves ____ feedback

Answer 14

postive

Question 15

When does hypothermia occur?

Answer 15

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

Question 16

As body temp decreases, the brain….

Answer 16

doesn’t work properly & shivering stops

Makes body temp. decrease even more

Question 17

Describe the role of positive feedback in hypothermia

Answer 17

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