Topic 6C - Homeostasis

Question 1

Can changes in our external environment affect our internal environment?

Answer 1

Yes

Question 2

What does homeostasis involve?

Answer 2

It involves the use of control systems to maintain our internal environment (within certain limits)

Question 3

Why is it important to maintain our internal environment?

Answer 3

To allow cells/proteins to function normally and to prevent them from being damaged.

Question 4

Give examples of 3 factors that need to be controlled in order to maintain our internal environment?

Answer 4

1. Temperature
2. pH
3. Glucose concentration

Question 5

How does temperature affect our internal environment?

and state the optimum temp for humans

Answer 5

1. Too high = enzymes may vibrate too much, breaking hydrogen bonds that holds them in their 3D shape. This changes shape of active site so it can’t fit into substrate (it denatures), so metabolic reactions are less efficient.
2. Too low = enzyme activity is reduced, slowing the rate of metabolic reactions.

Optimum temp in humans = 37

Question 6

How does pH affect our internal environment?

and state the optimum pH for humans

Answer 6

Too high/too low = hydrogen bonds that holds enzymes in their shape are broken. This changes shape of active site so it can’t fit into substrate (it denatures), so metabolic reactions are less efficient.

Optimum pH = pH 7 (but stomach enzymes work best at low pH’s)

Question 7

How does glucose concentration affect our internal environment?

Answer 7

Too high = water potential is reduced to a point where water molecules diffuse out of cells into blood by osmosis. This causes cells to shrivel up and die.

Too low = cells unable to carry out normal processes e.g. respiration, so less energy,

Question 8

What is negative feedback?

Answer 8

A mechanism that keeps things around the normal level

Question 9

What do homeostatic systems use?

Answer 9

They use receptors, a communication system, and effectors.

Question 10

How do homeostatic systems work?

(and what

Answer 10

1. Receptors detect a change, and info is communicated via nervous system or hormonal system to effectors.
2. Effectors responds to counteract change - bringing level back to normal. (negative feedback)

Question 11

What is the condition for negative feedback to work

Answer 11

CONDITION = Change must not be too large.

- Negative feedback only works within certain limits. if change is too big, effectors may not be able to counteract it.

Question 12

Does the body have only 1 negative feedback system or multiple negative feedback systems?

Answer 12

Multiple negative systems

Question 13

Why is it better to have multiple negative feedback systems than only 1 negative system.

Answer 13

Having more than 1 mechanism gives a faster response and more control over changes in your internal environment
- It allows you to actively increase or decrease a level so it returns to normal (If you only had 1 negative feedback mechanism, you’d only be able to change a level in 1 direction so it returns to normal.

Question 14

What are positive feedback systems?

Answer 14

They amplify a change from the normal level (The effectors respond to further increase the level away from the normal level).
- It isn’t involved in homeostasis.

Question 15

In what 2 situations is positive feedback used?

give examples

Answer 15

1. When a homeostatic system breaks breaks down (e.g. if you’re too cold for too long)
2. If you need to rapidly activate something (e.g. a blood clot after an injury)

Question 16

What happens in blood clots?

in terms of platelets and negative feedback systems

Answer 16

1. Platelets become activated and release chemical that trigger more platelets to be activated, and so on.
2. Platelets quickly form blood clot at injury site
3. The process ends with negative feedback, when the body detects the blood clot has been formed.

Question 17

How does hypothermia relate to positive feedback.

GRAPH

Answer 17

1. Hypothermia happens when heat’s lost from body, quicker than it can be produced.
2. As body temp falls, the brain doesn’t work properly and shivering stops - this makes body temperature fall even more.
3. Positive feedback takes body temp further away from the normal level, and it continues to decrease until action is taken.