Nervous System And The Eye

Question 1

What is the nervous system?

Answer 1

Consist of the brain and spinal cord (CNS), which coordinate the responses to the world around us by sending electrical impulses all around the body using nerve cells ie neurones

Question 2

What are synapes? How do they work?

Answer 2

The connection between two neurones

• the nerve signal is transferred by chemical which diffuse across the gap
• these chemicals then set off a new electrical signal in the next neurone

Question 3

What are reflexes?

Answer 3

Rapid, automatic responses for certain stimuli that dont invlove the conscious part of the brain - they can reduce the chances of being injured
- the passage of info in a reflex is called a reflex arc

Question 4

What are receptors? Give some examples.

Answer 4

Cells that detect a stimulus

- taste receptors on the tongue, and sound receptors in the ears

Question 5

What are effectors? Give examples

Answer 5

Respond to nervous impulses and bring about a change.

- muscle and glands are effectors

Question 6

What do the sensory, relay and motor neruone do?

Answer 6

Sensory - carries electrical impulses from receptor to spinal cord
Relay - picks up the impulses in the spinal cord
Motor - receives the impulse from the spinal cord & send it to a effector

Question 7

How does the reflex arc work?

Answer 7

1) . A stimulus is detected by receptors, impulses are sent along to a relay neurone in CNS
2) . Impulse reaches a synapse betweem the sensory and relay neurones, they trigger the chemical to be released & diffuse along to the relay neurone (neurotransmitter)
3) . Impulses reach a synapse between the relay and motor neruone, chemicals are released ans impulses are sent along the motor neurone
4) . Impulse travels along the motor neurone ro the effector
5) . The effector repsonds

Question 8

What is the central nervous system? What are all impulses?

Answer 8

A coordination centre that recieves info from the receptors and the coordinates a response which is carried out by effectors
- all impulses are identical

Question 9

Whats the independent variable?

Answer 9

The factor you are investigating/controlling

Question 10

What is the dependant variable?

Answer 10

The factor that changes as a result of your investigation/ what you are recording

Question 11

What is the control variable?

Answer 11

The factors you must keep the same throughout so the test is carried out accurately

Question 12

What are computer tests?

Answer 12

Used to measure reaction speeds, they test how quickly you can press a button/key when younsee an image on the screen

Question 13

What three things are computer tests?

Answer 13

• more accurate as they czn measure in milliseconds
• more precise as there is no human error
• no clues as you have no idea when the image will appear so you cant predict when to react. When a person tests you they may give you hints!

Question 14

What do the dendrites, axon, myelin sheath, and nerve endings do?

Answer 14

Dendrites - long extensions that stick out of the cell membrane, they detect the stimulus sent
Axon - a long structure like a tail, transports impulses quickly
Myelin sheath - rolls of fat tissue wrapped around the axon that speed up impulses + prevent any impulse leaking out.
Nerve endings - impulse leaves the neurone here as a chemical and can be passed on

Question 15

What does the retina and lens do?

Answer 15

Retina - contains receptors called rods and cones that are sensitive to light and colours
Lens - focuses the light that enters the eye onto the retina so it can be detected by receptors

Question 16

What does the pupil and sclera do?

Answer 16

Pupil - the hole in the eye that allows the light to enter

Sclera - strong, tough wall around the eye that provides support to the organ

Question 17

What do the cornea and iris do?

Answer 17

Cornea - a trasnparant outer layer that reflects light into the eye
Iris - muscles that control the size of the pupil and therefore controls how much light can enter the eye

Question 18

What does the optic nerve and ciliary muscles do?

Answer 18

Optic nerve - carries impulses from thr retinas receptors to the brain so the brain can make sense of what we’re looking at
Ciliary muscles - muscle fibres work with the suspensory ligaments to control the shape of the lens

Question 19

How do we see things?

Answer 19

1) . The lens refracts (bends) light producing an upside down image
2) . The receptors in the retina send an impulse along the sensory neurones in the optic nerve to the brain
3) . The back of the brain (occitpitual lobe) recieves the impulse & produces a corrected image we see

Question 20

What do the radial and circular muscles do?

Answer 20

Radial - radiate out from the pupil

Circular - go around and around the iris

Question 21

How does the eye respond to bright light?

Answer 21

1) . Light receptor on the retina detect bright light
2) . Circular muscles in the iris contract
3) . Radial muslces in the iris relax
4) . Pupil gets smaller
5) . Limits the amount of light that enters the eye

Question 22

How does the eye respond to dim light?

Answer 22

1) . Light receptors on the retina detect low light
2) . Circular muscles in the iris relax
3) . Radial muscles in the iris contract
4) . Pupil gets larger
5) . Allows more light to enter the eye

Question 23

What is accomodation?

Answer 23

When the lens changes shape in order to focus on the image correctly

Question 24

How does the eye see objects that are close to us?

Answer 24

1) . Ciliary muscles contract
2) . The ligaments become loose
3) . Lens gets fatter/more curved
4) . Causes greater refraction of light

Question 25

How does the eye see objects that are far away to us?

Answer 25

1) . Ciliary muscles relax
2) . Ligaments become tight
3) . Lens gets thinner/ stretched
4) . Causes less refraction of light

Question 26

What is myopia? How does it happen? What happens because of it?

Answer 26

Its short sightedness happens when the lens is the wrong shape or the eyeball is too long
- the light is refracted too much so the image is focused before it reaches the retina

Question 27

What is hyperopia? How does it happen? What happens because of it?

Answer 27

Its long sightedness, people cannot focus on objects close by as the lens is the wrong shape is the eyeball is too short
- the light isnt refracted enough meaning the image is focused behind the retina

Question 28

How can myopia and hyperopia be solved?

Answer 28

Myopia - wear glasses with a concave lens to correct it, so the light ray focuses on the retina
Hyperopia - wear glasss with convex lens to correct it, so the lens refracts the light rays to focus on the retina

Question 29

What happens to the eye with old age? What does this mean?

Answer 29

The lens in the eye begins to lose some flexibility, which means it will not be as able to form the correct shape to focus on objects at different distance

Question 30

How do contact lenses work?

Answer 30

They are thin lenses that sit on the surface of the eye and compensate for the faulty lens within the eye itself

Question 31

Why are contact lenses popular?

Answer 31

There’s lightweight, invisible and improve sight.

The soft lens is more popular than the hard lens as its more comfortable however it can be more prone to eye infections

Question 32

How does laser eye surgery work? How does it improve short and longsightedness?

Answer 32

Its used to remove tissure from the cornea,
SS- this makes the cornea thinner so it cant refract so much light and therefore improve short sightedness
LS - the surgery improves the amount of light refraction, allowing the imsge to be focused onto the retina

Question 33

What are the advantages and disadvantages of laser eye surgery?

Answer 33

A - very precise procedure- takes off the correct amount of tissue to correct eyesight
D - risk of complications/infection

Question 34

How do replacement lenses work?

Answer 34

The faulty natural lens is removed & replaces with an artificial plastic lens. The plastic is clear to allow light to enter

Question 35

What are the advantages and disadvantages of replacement lens?

Answer 35

A - sometime works more efficiently on longsightedness than laser eye surgery does
D - involves surgical work which inside the eye theres a greater risk of infection and complications that could damage eyesight