2.1.1 Homeostasis

Question 1

What is homeostasis?

Answer 1

The maintenance of a constant physiological state of the body despite fluctuations in the environment.

Question 2

What is homeostasis important for?

Answer 2

Ensures survival of an organism

Question 3

What is a stimulus?

Answer 3

A detectable change (input) in either the internal or external environment.

Question 4

What is a receptor?

Answer 4

Specialised cells that detect stimuli from the internal or external environment.

Question 5

What is an effector?

Answer 5

Any part of the body that responds to an efferent impulse from the brain or spinal cord.

Question 6

What is the purpose of a feedback system?

Answer 6

To act on a stimulus from one part of the body to cause a response which acts to alter the original stimulus.

Question 7

What are the two types of feedback systems?

Answer 7

• Negative feedback
• Positive feedback

Question 8

What does negative feedback do?

Answer 8

Restores the condition to a steady state by stopping or reducing the original stimulus.

Question 9

What does positive feedback do?

Answer 9

Forces an organism out of homeostasis by maintaining or increasing the direction of the stimulus.

Question 10

What happens during positive feedback?

Answer 10

Effectors respond by amplifying or producing more of the original stimulus until it ceases.

Question 11

What is a gland?

Answer 11

An organ that secretes chemicals or proteins within the body or externally.

Question 12

What is a muscle?

Answer 12

Tissue made up of long, thin fibres that contract when stimulated.

Question 13

Explain how negative feedback loops function using the example of the eye responding to too much light.

Answer 13

Light receptors detect too much light, send a message to the CNS, which sends a nerve impulse to the muscles in the eye (effector) causing the pupil to contract (response).

Question 14

Fill in the blank: A _____________ is a detectable change in the internal or external environment.

Answer 14

stimulus

Question 15

True or False: Negative feedback systems are the most common in the body.

Answer 15

True

Question 16

Fill in the blank: An effector can be either a _______ or a gland.

Answer 16

muscle

Question 17

What is detected by specialised cells found in sense organs (receptors)?

Answer 17

Stimuli

Question 18

Give two examples of effectors

Answer 18

Muscles which contract or relax
Glands which secrete hormones or other substances.

Question 19

Give an example of a negative feedback system

Answer 19

• maintaining sugar levels
• Maintaining internal temperature (endotherms)
• Maintaining pH levels of the blood

Question 20

Give an example of negative feedback

Answer 20

Childbirth
Lactation.
Bloodclotting