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Nervous System > Vision > Flashcards

Vision Flashcards

1
Q

Light rays bend to form a sharp image on the retina, this is known as

A

refraction

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2
Q

We can focus on near or distant objects by changing how much we bend the light rays, this is known as

A

accommodation

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3
Q

Sometimes there is a mismatch between how much we bend the light rays which leads to

A

refractive errors

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4
Q

An image is seen through

A

phototransduction

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5
Q

What is accommodation?

A

The ability to focus on objects which are far away or close by changing how much we bend the light rays

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6
Q

What three things comprise accommodation when focusing on something close and happen simultaneously?

A

Lens changes shape becoming thicker and more spherical
Pupils constrict
Eyes converge

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7
Q

Ciliary body contraction causes the ciliary body to

A

bulge - decreasing the space between the body and the lens

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8
Q

What effect does ciliary body contraction have on the suspensory ligaments and therefore the lens?

A

Suspensory ligaments become relaxed, the lens is no longer under stretch so becomes thicker

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9
Q

Is a thicker lens more or less powerful?

A

More

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10
Q

To sharpen the focus on an object, the pupil

A

constricts - to allow only a few rays from the object to pass through

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11
Q

What is the pupillary constrictor?

A

A concentric muscle around the border of the pupil which gets parasympathetic innervation

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12
Q

Eyes converge when

A

focusing on a close up object

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13
Q

What muscles of the eye are used to converge the eyes?

A

Medial recti muscles of both eyes

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14
Q

Why are the medial recti muscles thicker than the lateral recti muscles in humans?

A

Humans spend a lot of time focussing on close up objects e.g. when reading so the medial recti muscles are used more frequently

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15
Q

What is myopia?

A

Short sightedness

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16
Q

What is hyperopia?

A

Long sightedness

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17
Q

What is astigmatism?

A

Non-spherical curvature of the cornea or lens

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18
Q

What is presbyopia?

A

Long sightedness due to old age

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19
Q

What is emmetropia?

A

perfect vision

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20
Q

Myopia causes

A

close objects to look clear but distant objects to appear hazy

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21
Q

What is the most common cause of myopia?

A

Eyeball too long for the strength of lens and cornea

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22
Q

In myopia, when the cornea and lens bend the rays of light, the image is not formed on the retina but

A

in front of the retina

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23
Q

What are the common symptoms of myopia?

A

Headaches
Complaints from children of being unable to see board in classroom
Divergent squint in infants and pre-verbal children
Toddlers with loss of interest in sports and people

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24
Q

How is myopia corrected?

A

Biconcave lenses or laser eye surgery - decreases bending power

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25
Q

Hyperopia causes close objects to appear

A

hazy, while further away objects are clear

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26
Q

What are the symptoms of hyperopia?

A

Eye strain after reading/working

Convergent squint in children/toddlers

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27
Q

How is hyperopia treated?

A

Biconvex lenses or laser eye surgery

28
Q

What does astigmatism cause?

A

Close and distant objects to appear hazy, due to the surface of the eye having different curvatures in different medians

29
Q

How is astigmatism corrected?

A

Using cylindrical glasses which are curved in only one axis, laser eye surgery or toric lenses

30
Q

What happens to the lens in presbyopia?

A

With increasing age the lens becomes less mobile and less elastic, ciliary muscle still contracts but the lens is more rigid so less able to change its shape

31
Q

How is presbyopia corrected?

A

Biconvex glasses/lenses for reading

32
Q

What is phototransduction?

A

The conversion of light energy into an electrochemical response by the photoreceptors (rods and cones)

33
Q

Visible light is an

A

electromagnetic wave

34
Q

The phototransduced rods and cones activate

A

the optic nerve neurons which generate an action potential which is transmitted to the brain

35
Q

What is rhodopsin?

A

A visual pigment found in the rods of the retina - extremely sensitive to light so enables vision in low lighting

36
Q

What will any condition affecting vitamin A absorption affect?

A

Vision, cause night blindness as well as abnormal conjunctiva and corneal epithelium

37
Q

What two types of light-sensitive cells are contained in the retina?

A

Rods and cones

38
Q

Rods work in

A

low light conditions to help with vision at night

39
Q

Cones work in

A

daylight and are responsible for colour discrimination

40
Q

Colour blindness is usually caused by

A

faulty cones or a defect in the pathway from the cone to the brain

41
Q

In increased illumination, the parasympathetic system causes the pupils to

A

constrict

42
Q

In low illumination, the sympathetic system causes the pupils to

A

dilate

43
Q

What muscles are responsible for the change in pupil diameter?

A

Constrictor pupillae and dilator pupillae

44
Q

All fibres from the eye pass through the

A

optic nerve to the optic chiasm

45
Q

The optic chiasm sits on top of the

A

pituitary gland

46
Q

At the optic chiasm the medial nasal fibres

A

cross to the opposite side

47
Q

The optic tract contains fibres from

A

the temporal half of the ipsilateral eye and the nasal fibres from the contralateral eye

48
Q

Fibres from the optic tract synapse at the

A

Lateral Geniculate Body

49
Q

From the lateral geniculate body, the optic radiation passes

A

behind the internal capsule to reach the primary visual cortex

50
Q

What lobe is the primary visual cortex found in?

A

Occipital

51
Q

The right visual cortex sees

A

the left half of the visual field

52
Q

The intrinsic muscles of the eye control

A

pupil diameter and help alter the lens curvature in order to see close objects

53
Q

The extrinsic muscles of the eye control

A

eye movement

54
Q

Name the 6 extra ocular muscles

A 
Medial rectus 
Lateral rectus
Inferior rectus 
Superior rectus
Inferior oblique 
Superior oblique
55
Q

The recti muscles of the eye arise from

A

the apex of the orbit from an annular fibrous ring

56
Q

The superior oblique arises from

A

the roof of the orbit, posteriorly

57
Q

The inferior oblique arises from the

A

floor of the orbit, anteriorly

58
Q

What muscle runs superiorly to and elevates the upper eyelid?

A

Levator palpebrae superioris

59
Q

When the eye is abducted, the superior rectus causes

A

elevation

60
Q

When the eye is adducted, the superior rectus causes

A

intorsion

61
Q

When the eye is abducted, the inferior rectus causes

A

depression

62
Q

When the eye is adducted, the inferior rectus causes

A

extorsion

63
Q

When the eye is adducted, the superior oblique causes

A

depression

64
Q

When the eye is adducted, the inferior oblique causes

A

elevation

65
Q

The medial rectus causes

A

adduction

66
Q

The lateral rectus causes

A

abduction

Nervous System (44 decks)

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