3.4.6 Homeostasis and Negative Feedback Flashcards Preview

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Flashcards in 3.4.6 Homeostasis and Negative Feedback Deck (20)
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1

What is meant by homeostasis?

Maintenance of a stable internal environment

2

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

  • 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

3

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

Enzyme activity is reduced = slows rate of metabolic reactions

4

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

  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

5

Explain what happens when the blood glucose levels are too high

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

6

Explain what happens when the blood glucose levels are too low

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

7

What is negative feedback?

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

8

Negative feedback only works within certain ___

limits

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

9

Homeostasis involves _____ negative feedback mechanisms

multiple

10

Why does homeostasis involve multiple negative feedback mechanisms?

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

11

1 negative feedback mechanism means ___ ____ and ___ ____

slower response and less control

12

What does postive feedback do?

Amplifies a change from the normal level

13

What does postive feedback cause effectors to do?

Effectors respond to further increase the level away from normal level

14

What is postive feedback useful for?

Useful to rapidly activate something

e.g. blood clot after injury

15

Positive feedback is ___ involved in homeostasis

NOT

16

When does positive feedback also occur?

When homeostatic system breaks down

e.g. of you're too cold for too long

17

Hypothermia involves ____ feedback

postive

18

When does hypothermia occur?

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

19

As body temp. ↓, brain....

doesn't work properly & shivering stops

Makes body temp. ↓ even more

20

Describe the role of positive feedback in hypothermia

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

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