U3 Homeostasis: Overview

Question 1

Define homeostasis

Answer 1

The maintenance of a constant internal environment despite fluctuations in the external environment

Question 2

Define feedback system

Answer 2

A circular situation in which the body responds to a stimulus, with the response altering the original stimulus and therefore providing feedback

Question 3

What are the steps of a feedback system?

Answer 3

1. Stimulus:
   internal/external change in the environment that causes a response
2. Receptor:
   sensory cells that detect a stimulus and convert it into a nerve impulse

Message:
receptors generate a message in the form of a nerve impulse or hormone

3. Modulator:
   control centre that processes the message received from the receptor

Message:
a new message is sent out by the modulator

4. Effector:
   muscle or gland that receives the message from the modulator
5. Response:
   the effector brings about an appropriate reaction
6. Feedback:
   the response changes the original stimulus

Question 4

Distinguish between positive and negative feedback

Answer 4

Positive feedback
- feedback that reinforces or amplifies the original stimulus
- not involved in homeostasis
- EG: fever, blood clotting

Negative feedback
- feedback that reduces or eliminated the effect of the original stimulus
- involved in homeostasis
- EG: