5.1.2- Homeostasis

Question 1

What is an effector? (3 examples included)

Answer 1

A cell, tissue or organ that brings about a response

Question 2

What is homeostasis

Answer 2

Maintaining a CONSTANT internal environment, despite the changes in external and internal factors.

Question 3

What is Negative feedback?

Answer 3

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

What are some of the aspects maintained by homeostasis? (6 points)

Answer 6

1) Body temperature
2) Blood glucose concentration
3) Blood salt concentration
4) Water potential of the blood
5) Blood pressure
6) Carbon dioxide concentration

Question 7

What is the standard response pathway for homeostasis?

Answer 7

Stimulus -> Receptor -> Communication pathway (cell signalling) -> effector -> response

Question 8

Name an example of a sensory receptor and define it (2 points - internal and external)

Answer 8

• Temperature receptor, these receptors may be on the surface of the body such as temperature receptors in the skin. They monitor changes in the external environment
• Other receptors are internal to monitor conditions inside the body, temperature receptors in the brain. When a change is detected a change will be stimulated to send a message to an effector

Question 9

How do the signals from the sensory receptor travel to the effector?

Answer 9

A communication system is required such as the neuronal system or the hormonal system. This acts by signalling between cells.

Question 10

How to cells transmit a message from the receptor cells to the effector cells?

Answer 10

Coordination centre, usually in the brain

Question 11

What are the messages from the receptor to the coordination centre called?

Answer 11

Input

Question 12

What are the messages from the receptor the coordination centre called?

Answer 12

Output

Question 13

What is feedback?

Answer 13

Effectors respond the the output from the coordination centre, bring about a response that will change the conditions inside the body.
These changes are then detected by receptors, in other words the input changes.

Question 14

For negative feedback to work, a number of processes must occur, what are they? (3 points)

Answer 14

1) A change to the internal environment must be detected
2) The change must be signalled to other cells
3) There must be an effective response that reverses the change in conditions.

Question 15

What is overshoot?

Answer 15

When a stimulus occurs, it may take time to respond and the response may cause a slight overshoot

Question 16

What is an example of positive feedback being harmful to the body

Answer 16

Enzymes become less active below core body temperature -> exergonic reactions that release heat are slower and release less heat. Body cools further and slow the enzymes controlled reactions even more. This causes the body temperature to spiral downwards.

Question 17

What is an example where positive feedback is beneficial (5 points)

Answer 17

At the end of pregnancy to bring about dilation of the cervix. -> As the cervix begins to stretch this causes the posterior pituitary gland to secrete the hormone Oxytocin. -> increases the uterine contraction which stretch the cervix more –> causes more secretion of more oxytocin. Once oxytocin is fully dilated, the baby can be born.
birth ends in production of oxytocin

and the Activity of neurones also relies on positive feedback.