homeostasis and response

Question 1

Define homeostasis

Answer 1

the regulation of internal conditions to maintain a stable internal environment

Question 2

Name the 3 things that homeostasis has to control to maintain a stable environment

Answer 2

1) water levels
2) body temperature
3) blood glucose concentration

Question 3

Explain how negative feedback counteracts when levels of something (e.g water or temperature) are too high

Answer 3

RECEPTORS detect a a stimulus levels is too high

COORDINATION CENTRE receives and processes the information then organises a response.

EFFECTORS carry out response so levels drop which counteracts the change which restores optimum level.

Question 4

Explain how negative feedback counteracts when levels of something (e.g water or temperature) are too high

Answer 4

RECEPTORS detect stimulus level is too low.

COORDINATION CENTRE receives and processes the information then organises a response..

EFFECTORS carry out response so levels decrease to counteract the change which restores optimum level.

Question 5

What are receptors? give an example

Answer 5

The cells that detect stimuli.

e.g taste receptors on tongue
sound receptors in ears

Question 6

What makes up the Central Nervous system in mammals?

Answer 6

Brain
Spinal cord

Connected to the body by:
Sensory neurones
Motor neurones

Question 7

What are sensory neurones?

Answer 7

Neurones that carry information as electrical impulses from receptors to the CNS.

Question 8

What are the motor neurones?

Answer 8

Neurones that carry information as electrical impulses from the CNS to the ffectors.

Question 9

What are the effectors?

Answer 9

Muscles which contract in response to a nervous impulse or glands that secrete hormones in response.

Question 10

Explain what happens in the nervous system when a bird sees a cat.

Answer 10

The receptors in the bird’s eye are stimulated.
Sensory neurones carry the information (as electrical impulses) from receptors to CNS.
CNS decides what to do about it.
The CNS sends information to the bird’s wings (the effectors) via motor neurones.
The muscles contract and the bird flies away to safety.

Question 11

How does information moves between neurones?

Answer 11

Electrical impulse travels along to the end of neurone where it triggers the release of chemicals which diffuse across the synapse to the next neurones which then set of a new electrical impulse.

Question 12

What are reflex actions?

Answer 12

Actions that are automatic and do not involve the conscious part of the brain.

Question 13

Explain the stages of the reflex arc

Answer 13

A stimulus is detected by the receptors.
Impulses are sent along a sensory neurone which triggers chemicals to diffuse across synapse to the relay neurone (in CNS) to set of new electrical impulse.
When impulse reaches a synapse between relay neurone and motor neurone the same thing happens (electrical-chemical-electrical).
Impulse travel along motor neurone to the effector (e.g a muscle which contracts to pull limb away from danger).

Question 14

Define:

cornea
iris
pupil
lens

Answer 14

Cornea- transparent outer layer that refracts light into eye

Iris- contains muscles that allow it to control the diameter of the pupil therefore how much light enters

Pupil- hole in middle of eye and allows light through

Lens- focuses light onto retina. It changes shape to see objects near and far.

Question 15

What is the job of:

sclera
retina
ciliary muscles and suspensory ligaments
optic nerve

Answer 15

Sclera- tough, supporting wall of eye

Retina- contains receptors that are sensitive to light intensity and colour

Ciliary muscles and suspensory ligaments control the shape of the lens

Optic nerve- carries impulses from retina to the brain

Question 16

How does the eye accommodate when focusing on a near object?

Answer 16

Ciliary muscles contract, which slacken suspensory ligaments. Lens becomes more curved which increases the amount by which it refracts light.

Question 17

How does the eye accommodate when focusing on a far object?

Answer 17

The ciliary muscles relax, which allows suspensory ligaments to pull tight. Lens becomes less curved so it refracts light by a less amount.

Question 18

What happens when bright light hits your eye?

Answer 18

When light receptors in the eye detect bright light, a reflex triggers the pupil to become smaller. The circular muscles in the iris contract and the radial muscles relax which reduces amount of light that can enter eye.

Question 19

What does the eye do in dim light?

Answer 19

The opposite: The circular muscles relax and the radial muscles contract which makes the pupil wider (dilated)

Question 20

Explain why some people are long sighted (hyperopia)?

Answer 20

The lens is the wrong shape and doesn’t refract enough or the eyeball is too short. The images of near objects are brought into focus behind the retina.

Question 21

What glasses would people with long-sightedness (hyperopia) wear?

Answer 21

Convex lens (curves outwards) which refracts light rays so they focus on retina.

Question 22

Explain why some people are short sighted (myopia)?

Answer 22

The lens is wrong shape and refracts too much or eyeball is too long. The images of distant objects are brought to focus in front of the retina.

Question 23

What glasses would people with short-sightedness (myopia) wear?

Answer 23

Concave lens (curves inwards) so that light rays focus on the retina.

Question 24

What new technologies are treatments for eye defects?

Answer 24

.Contact lenses
.Laser eye surgery
.Replacement lens surgery

Question 25

Compare hard and soft contact lenses.

Answer 25

Soft contact lenses are more comfortable but carry a higher risk of infection.

Question 26

What are the benefits of contact lenses?

Answer 26

.Lightweight
.Almost invisible
.Convenient for activities like sport

Question 27

How can laser eye surgery help myopia and hyperopia? Give 2 negatives.

Answer 27

For short sightedness, they slim down the shape of the cornea making it less powerful.

For long sightedness, they change the shape of the cornea so that it’s more powerful.

Negatives:
.infection
.eyes react in a way that makes vision worse

Question 28

What is replacement lens surgery? Give a negative.

Answer 28

Treats hyperopia.
The natural lens of the eye is removed and replaced by and artificial lens made of clear plastic.

Negative- possible damage to retina (could lead to loss of sight)

Question 29

What is the function of the cerebral cortex?

Answer 29

Responsible for things like consciousness, personality, intelligence, memory, language

Question 30

What is the function of the cerebellum?

Answer 30

Responsible for muscle coordination and balance.

Question 31

What is the function of the medulla?

Answer 31

Responsible for unconscious activities like breathing, heartbeats