Homeostasis

Question 1

What is an effector?

Answer 1

A cell, tissue or organ that brings about a response.

Question 2

Define homeostasis.

Answer 2

Maintaining a constant internal environment despite changes in external and internal factors.

Question 3

What is negative feedback?

Answer 3

The mechanism that reverses a change, bringing the system back to the optimum.

Question 4

What is positive feedback?

Answer 4

The mechanism that increases a change, taking the system further away from the optimum.

Question 5

What are sensory receptors?

Answer 5

Cells/sensory nerve endings that respond to a stimulus in the internal or external environment of an organism and can create action potentials.

Question 6

Give six aspects maintained by homeostasis.

Answer 6

Body temperature
Blood glucose concentration
Blood salt concentration
Water potential of the blood
Blood pressure
Carbon dioxide concentration

Question 7

What is the standard response pathway?

Answer 7

Stimulus -> receptor -> communication pathway (cell signalling) -> effector -> response

Question 8

Give an example of a sensory receptor.

Answer 8

Temperature receptors.

Question 9

Where are temperature receptors found in the body?

Answer 9

On the surface of the body (skin)

Temperature receptors in the brain

Question 10

Give an example of a communication system in the body.

Answer 10

The neuronal system or the hormonal system.

Question 11

How do the communication systems work?

Answer 11

By signalling between cells.

Question 12

The messages from the receptor to the coordination centre are known as what?

Answer 12

The input

Question 13

What are the messages sent to the effectors calls?

Answer 13

The output

Question 14

Give examples of effectors.

Answer 14

Liver cells

Muscle cells

Question 15

Where is the coordination centre usually?

Answer 15

In the brain.

Question 16

Explain the flow diagram of negative feedback.

Answer 16

Change away from optimum -> Receptors detect change -> communication system informs effector -> effector reacts to reverse change -> return to optimum condition -> receptors detect a reduction in stimulus -> reduce the input to the coordination centre -> output from coordination centre to effectors reduces -> effectors reduce their activity.

Question 17

For negative feedback to work what processes must occur?

Answer 17

A change to the internal environment must be detected.
The change must be signalled to other cells.
There must be an effective response that reverses the change in condition.

Question 18

When is positive feedback used?

Answer 18

To stimulate an increase in change.

Question 19

Give two examples of positive feedback.

Answer 19

Dilation of the cervix during labour due to the secretion of the hormone oxytocin.
The activity of neurones also relies on positive feedback.

Question 20

What does oxytocin increase during labour?

Answer 20

The uterine contractions which stretch the cervix more.