The Nervous System and the Eye

Question 1

What is a neurone?

Answer 1

Specialised cells which transmit information through nerve responses

Question 2

What is a nerve?

Answer 2

A bundle of several neurones

Nerve cell = a single neurone

Question 3

What is a nerve impulse?

Answer 3

Electrical signal (current) that travels along a neurone

Question 4

Two examples of reflexes

Answer 4

Knee jerk reflex

Pupil reflex

Question 5

What is the cell body?

Answer 5

The part of a neurone which contains the nucleus

Question 6

What is the dendrite?

Answer 6

Extensions at which nerve impulses are received from other cells at synapses and transmitted to the cell body

Question 7

What is the axon?

Answer 7

Extension which carries nerve impulses to other neurone or effector organ (muscle or gland)

Question 8

What is the myelin sheath?

Answer 8

Fatty sheath which insulates the axon (preventing short-circuits of electrical impulses) and speeds up the conduction of nerve impulses, made of Schwann cells

Question 9

What are the steps of the reflex arc?

Answer 9

• Stimulus (could be pain)
• Receptor
• Sensory neurone (anywhere where you feel sense)
• Relay neurone (in the central nervous system)
• Motor neurone
• Effector (muscle, gland)
• Response

Question 10

Way to remember the reflex arc?

Answer 10

Steve 
Receives 
Stamps 
Regularly 
Meanwhile
Emily 
Runs

Question 11

What is a reflex?

Answer 11

Involuntary and almost immediate response to a stimulus

Question 12

What does the central nervous system consist of and how is it linked to the sense organs?

Answer 12

The brain and the spinal cord are the two parts of the central nervous system. They are linked to the sense organs by nerves

Question 13

What are the three parts of the spine?

Answer 13

Intervertebral disc
Spinal cord
Vertebral column (encloses and protect the spinal cord)

Question 14

What is a synapse?

Answer 14

A tiny gap between 2 neurones across which impulses pass by diffusion of a neurotransmitter

Question 15

What is are neurotransmitters?

Answer 15

Chemicals that transmit signals from one neurone to another across a synapse

Question 16

Two examples of diseases linked to defective neurotransmitter function

Answer 16

Schizophrenia

Depression

Question 17

Steps of transmitting of a nerve impulse across a synapse

Answer 17

• Nerve impulse travels along the axon to the synapse in the form of an electrical signal
• The vesicles containing the neurotransmitters move to the membrane of the axon terminal
• Neurotransmitter is emptied into the synapse
• Neurotransmitter diffuses across the synapse
• Neurotransmitter binds to the receptor on the surface of the dendrite
• Binding of the neurotransmitter triggers a new nerve impulse
• The nerve impulse travels along the dendrite to the axon

Question 18

What is the function of the conjunctiva in the eye? And what is it?

Answer 18

It is a layer covering the cornea and sclera

Helps lubricate the eye

Question 19

What is the function of the cornea in the eye? And what is it?

Answer 19

It is a clear covering over the eye

Helps refract and focus light

Question 20

What is the function of the lens in the eye? And what is it?

Answer 20

It a transparent structure behind the pupil

Refracts and focuses light

Question 21

What is the function of the pupil in the eye? And what is it?

Answer 21

It is a hole in the centre of the iris

Controls the amount of light entering the eye

Question 22

What is the function of the iris in the eye? And what is it?

Answer 22

It is a pigmented tissue

Controls the amount of light entering the eye

Question 23

What is the function of the suspensory ligaments in the eye? And what are they?

Answer 23

They are ligaments connecting the ciliary muscle and the lens
Involved in controlling accommodation

Question 24

What is the function of the ciliary muscle in the eye? And what is it?

Answer 24

It is a ring of muscle connected to the lens via suspensory ligaments
Controls accommodation

Question 25

What is the function of the retina in the eye? And what is it?

Answer 25

It is the inner layer of the eye containing photoreceptors (rods + cones) Responds to light stimulus

Question 26

What is the function of the optic nerve in the eye? And what is it?

Answer 26

It is a sensory nerve (part of the CNS) | Carries nerve impulses from retina to brain

Question 27

What process happens to the pupil in dim light which allows it to dilate?

Answer 27

- The stimulus of a dim light is picked up by the retina which sends a nerve signal to the optic nerve. - The optic nerve acts as a sensory neurone and sends the signal to the CNS - The nerve signal goes through a relay neurone and into a motor neurone - The signal is sent to the muscles in the iris which respond

Question 28

What are the muscles in the iris?

Answer 28

Radial muscles | Circular muscles

Question 29

What happens in the iris when in dim light?

Answer 29

- Radial muscles contract - Circular muscles relax - Pupil dilates (gets bigger)

Question 30

What happens in the iris when in bright light?

Answer 30

- Radial muscles relax - Circular muscles contract - Pupil gets smaller

Question 31

What do rods do in the retina?

Answer 31

Help with vision in dim light

Question 32

What do cones do in the retina?

Answer 32

Provide colour vision

Question 33

What is accommodation in the eye?

Answer 33

The reflex that makes the eye focus on an object by changing the shape of its lens

Question 34

What happens to light that is reflected from an object?

Answer 34

The light is refracted (bent) by the cornea and the lens forming an upside down image on the retina

Question 35

What causes short sightedness and how can it be cured?

Answer 35

The eye is too long so the point of focus is before the retina Corrective concave lenses are used

Question 36

What causes far sightedness and how can we cure it?

Answer 36

The eye is too short so the point of focus is behind the retina Corrective convex lenses are used