6C - Homeostasis basics

Question 1

What is homeostasis?

Answer 1

The maintenance of a constant (stable) internal environment within a living organism.

Question 2

What can changes in your external environment affect?

Answer 2

Your internal environment - the blood and tissue fluid that surrounds your cells.

Question 3

What does homeostasis involve?

Answer 3

Control systems that keep your internal environment roughly constant (within certain limits).

Question 4

What is keeping your internal environment stable, vital for?

Answer 4

Cells to function normally and to stop them being damaged.

Question 5

What is controlled in homeostasis?

Answer 5

Core body temperature.
Blood pH.
Blood glucose levels.

Question 6

Why does body temperature need to be controlled by homeostasis?

Answer 6

• If it is too high, enzymes may become denatured.
• If it is too low, enzyme activity is reduced, slowing the rate if metabolic reactions.
• The highest rate of enzyme activity happens at their optimum temperature.

Question 7

Explain how an enzyme becomes denatured if body temperature is too high

Answer 7

The enzyme’s molecules vibrate too much, which breaks the hydrogen bonds that hold them in their 3D shape. The shape of the enzyme’s active site is changed and it no longer works as a catalyst. This means metabolic reactions are less efficient.

Question 8

Why does pH need to be controlled by homeostasis?

Answer 8

If blood pH is too high or too low (highly alkaline or acidic) enzymes become denatured. This means metabolic reactions are less efficient.

Question 9

Explain how an enzyme becomes denatured if pH is too high/low

Answer 9

The hydrogen bonds that hold them in their 3D shape are broken, so the shape of the enzyme’s active site is changed and it no longer works as a catalyst.

Question 10

At what pH does the highest rate of enzyme activity happen?

Answer 10

At their optimum pH - usually around pH 7 (neutral), but some enzymes work best at other pHs, e.g. enzymes found in the stomach work best at a low pH.

Question 11

Why is important to maintain the right concentration of glucose in the blood?

Answer 11

• Because cells need glucose for energy.

- Blood glucose concentration also affects the water potential of blood.

Question 12

What is water potential?

Answer 12

The potential (likelihood) of water molecules to diffuse out of or into a solution.

Question 13

Why does glucose need to be controlled by homeostasis?

Answer 13

• If blood glucose concentration is too high the water potential of blood is reduced to a point where water molecules diffuse out of cells into the blood by osmosis. This can cause the cells to shrivel up and die.
• If blood glucose concentration is too low, cells are unable to carry out normal activities because there isn’t enough glucose for respiration to provide energy.

Question 14

What can homeostasis be controlled by?

Answer 14

Nervous system
Endocrine system
A combination of the two

Question 15

How do homeostatic systems detect a change and respond?

Answer 15

By negative feedback.

Question 16

What do homeostatic systems involve?

Answer 16

Receptors, a communication system and effectors.

Question 17

What do receptors do in a homeostatic system?

Answer 17

Detect when a level is too high or too low.

Question 18

Where is the information from a receptor communicated in a homeostatic system?

Answer 18

To the effectors.

Question 19

How is the information from a receptor communicated to the effectors in a homeostatic system?

Answer 19

Via the nervous or the hormonal system.

Question 20

What do the effectors in a homeostatic system do?

Answer 20

Respond to counteract the change - bringing the level back to normal.

Question 21

What is the mechanism that restores the level back to normal in a homeostatic system called?

Answer 21

A negative feedback mechanism.

Question 22

What is the negative feedback mechanism?

Answer 22

The mechanism that restores the level back to normal in a homeostatic system.

Question 23

What does negative feedback do?

Answer 23

Keeps things around the normal level.

Question 24

Negative feedback only works…

Answer 24

Within certain limits.

Question 25

When does negative feedback not work?

Answer 25

If the change is too big then the effectors may not be able to counteract it.

Question 26

Why does homeostasis involve multiple negative feedback mechanisms for each thing being controlled?

Answer 26

Because having more than one mechanism gives more control over changes in your internal environment than just having one negative feedback mechanism.

Question 27

What does having multiple negative feedback mechanisms means you can do?

Answer 27

Actively increase or decrease a level so it returns to normal.

Question 28

Only have one negative feedback mechanism would mean what?

Answer 28

A slower response and less control.

Question 29

What does a positive feedback mechanism do?

Answer 29

Amplifies the change.

Question 30

What do effectors do in a positive feedback mechanism?

Answer 30

Respond to further increase the level away from the normal level.

Question 31

Why is positive feedback useful?

Answer 31

To rapidly activate something, e.g. a blood clot after injury.

Or in the labour point of pregnancy.

Question 32

When can positive feedback happen?

Answer 32

When a homeostatic system breaks down, e.g. if you’re too cold for too long.

Question 33

Why isn’t positive feedback involved in homeostasis?

Answer 33

Because it doesn’t keep your internal environment stable.

Question 34

How do endotherms maintain body temp?

Answer 34

Maintain body temp at a set point.

Generate heat energy through respiration.

Change cellular and physiological processes.

Question 35

How do ectotherms maintain body temp?

Answer 35

Mostly rely on external heat energy.

Warm or cool their body by changing their behaviour in response to changing conditions.

Expose themselves to the sun (basking).

Take shelter.

Gaining warmth from the ground.

Question 36

How do endotherms gain heat?

Answer 36

Vasoconstriction
Shivering
Raising of hair
Increased metabolic rate
Decrease in sweating
Behaviour

Question 37

How do endotherms lose heat?

Answer 37

Vasodilation
Increase sweating
Lowering of body hair
Behavioural mechanisms