Homeostasis

Question 1

Homeostasis

Answer 1

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

Question 2

Aspects maintained by homeostasis

Answer 2

• body temperature
• blood glucose concentration
• blood salt concentration
• water potential of blood
• blood pressure
• carbon dioxide concentration

Question 3

What is the response pathway?

Answer 3

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

Question 4

Sensory receptors

Answer 4

may be on surface of skin, they monitor the external environment and when they detect change it will be stimulated to send response to an effector.

Question 5

Communication system e.g neuronal/ hormonal works by

Answer 5

signalling between cells.
Transmits messages from the receptor cells to the effector cells via a coordination centre usually the brain.

Question 6

What is the input?

Answer 6

The messages from the receptor to the coordination centre.

Question 7

What is the output?

Answer 7

The messages sent to the effectors.

Question 8

What is an effector?

Answer 8

Cells such as liver cells or muscle cells that bring about a response.

Question 9

What is negative feedback

Answer 9

The mechanism of reversing a change bringing the system back to optimum.

Question 10

How does negative feedback work?

Answer 10

• receptor detects a change
• there is an input
• the communication system informs the effector
• there is an output
• effector reacts to reverse change
• return to optimum condition
• optimum condition
• change away from optimum
  cycle continues

Question 11

What are the processes that negative feedback needs to occur?

Answer 11

• A change in internal environment must be detected
• The change must be signalled to other cells

Question 12

Benefit of negative feedback

Answer 12

It can maintain a reasonably constant set of condition it may never remain perfectly constant there will be some variation around the optimum condition.

Question 13

What is positive feedback?

Answer 13

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

Question 14

Why is positive feedback usually harmful?

Answer 14

It destabilises the system.

Question 15

How does positive feedback work?

Answer 15

• Optimum condition
• change away from optimum
• receptor detects change
• there is an input
• communication system informs effector
• There is an output
• the effector reacts to increase change
• cycle continues bak to another change away from the optimum

Question 16

When is positive feedback beneficial?

Answer 16

As positive feedback is used to stimulate an increase in a change.
Is used to bring about dilation of cervix at the end of a pregnancy.
- as cervix begins to stretch causes the pituitary gland to produce more oxytocin.
- oxytocin increases uterine contractions which streets the cervix more.
- Birth ends the production of oxytocin.

Question 17

What does the activity of neurones rely on?

Answer 17

positive feedback.