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LCRS Neuroscience > Neurology of the visual system > Flashcards

Neurology of the visual system Flashcards

1
Q

Where does the visual pathway transmit a signal from and to?

A

From the eye to the optic chiasm

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2
Q

Which cranial nerve is the optic nerve?

A

2

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3
Q

What happens at the optic chiasm?

A

Half of the optic nerve fibres cross

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4
Q

What do ganglion nerve fibres exit the optic chiasm as?

A

The optic tract

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5
Q

Where do ganglion nerve fibres originate?

A

Retina

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6
Q

Where do ganglion nerve fibres synapse with the next order neurone?

A

Lateral geniculate nucleus

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7
Q

Where is the lateral geniculate nucleus?

A

In the thalamus

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8
Q

What is the optic radiation?

A

4th order neurone that relays signals to the primary visual cortex in the occipital lobe for visual processing

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9
Q

Where does the primary visual cortex (striate cortex) relay information to?

A

Extra striate cortex

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10
Q

In the retina part of the visual pathway, what are the first order neurones?

A

Rod and cone retinal photoreceptors

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11
Q

What are second order neurones?

A

Bipolar cells

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12
Q

What are third order neurones?

A

Retinal ganglion cells

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13
Q

What is the receptive field of a retinal neurone?

A

Retinal space within which incoming light can alter the firing pattern of a neurone

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14
Q

Do rods or cones have bigger receptive fields?

A

Rods- high sensitivity

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15
Q

Do rods or cones synapse less upon the same ganglion cells?

A

Cones- high visual acuity

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16
Q

What is an on-centre ganglion cell?

A

It is stimulated by light falling on the centre of its receptive field and inhibited by light falling on the edge of its receptive field

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17
Q

What is an off-centre ganglion cell?

A

It is inhibited by light on centre of receptive field and stimulated by light on edge

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18
Q

What does this have an important role in?

A

Contrast sensitivity and enhanced edge detection

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19
Q

What is the difference between lesions anterior or posterior to the optic chiasm?

A

Lesions anterior to the optic chasm affect one eye

Posterior affects both eyes

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20
Q

Where do the 53% of fibres that cross at the optic chasm originate from?

A

Nasal retina

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21
Q

What is it called where lesions lead to problems in both eyes?

A

Bitemporal hemianopia

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22
Q

What are the two divisions of the optic radiation and where do they travel?

A

Upper division - through the parietal lobe (inferior visual quadrants)
Lower division- through the temporal lobe (superior visual quadrants)

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23
Q

What is the Meyer’s loop formed from?

A

Lower division loops

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24
Q

What will a Meyer’s loop lesion lead to?

A

Vision loss in one of the superior quadrants (superior homonymous quadrantopia)

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25
Q

What is the most common cause of bitemporal hemianopia?

A

Enlargement of the pituitary gland which sits within the sella turcica beneath the optic chiasm

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26
Q

Where is the primary visual cortex situated?

A

Along the calcarine sulcus within the occipital lobe

27
Q

What part of vision is PVC above the calcarine sulcus responsible for?

A

Inferior visual field

28
Q

What is the main cause of damage to the primary visual cortex?

A

Strokes

29
Q

What does the extrastriate cortex do?

A

Converts basic visual information to position and orientation

30
Q

How does the pupil regulate light input?

A

In light, the iris circular muscle contracts and there is constriction of the pupillary aperture which reduces light entering the eye and reduces the amount of photopigment bleaching which increases the depth of field

31
Q

Where do the retinal ganglion cells involved in the pupillary light reflex leave the optic tract and synapse?

A

They exit the posterior 1/3 before the lateral geniculate nucleus and synapse upon the dorsal brainstem- pretectal nucleus

32
Q

What happens at the Edinger-Westphal nucleus?

A

The afferent pathway from each eye synapses there on both sides of the brainstem

33
Q

What provides the efferent pathway of the pupillary reflex?

A

Parasympathetic nerve that originates at the Edinger-Westphal nucleus and synapses at the ciliary ganglion with the short posterior ciliary nerve which then directly innervates the iris pupillary sphincter

34
Q

Will light in the left eye stimulate the pupillary reflex in the right eye?

A

Yes- both eyes

35
Q

What is an example of an afferent deficit?

A

Damage to the optic nerve

36
Q

What happens in an afferent deficit?

A

No constriction in either eye when affected eye is stimulated but normal constriction in both eyes when unaffected eye is stimulated

37
Q

What happens in an efferent deficit?

A

There is no constriction in affected eye when either eye is stimulated and the unaffected eye constricts both times

38
Q

How do you test for a relative afferent pupillary deficit>

A

Swinging torch test

39
Q

What is duction?

A

Movement in one eye

40
Q

What is version?

A

Simultaneous movement of both eyes in same direction

41
Q

What is vergeance?

A

Simultaneous movement of eyes in opposite directions

42
Q

What is convergence?

A

Simultaneous adduction movement of both eyes when viewing a near object

43
Q

What is a saccade?

A

Short fast burst

44
Q

What is smooth pursuit?

A

Sustained slow movement

45
Q

What are the six extra-ocular muscles?

A 
Superior rectus
Inferior rectus
Superior oblique
Inferior oblique
Lateral rectus
Medial rectus
46
Q

Which muscle does the trochlear nerve innervate?

A

Superior oblique

47
Q

Which muscle does the abducens innervate?

A

Lateral rectus

48
Q

Which muscles does the oculomotor innervate

A

Inferior oblique, superior rectus, inferior rectus and medial rectus

49
Q

Where do all the rectus muscles originate from?

A

Common tendinous ring behind the eye at the orbital apex

50
Q

Where do the rectus muscles insert?

A

Sclera of the anterior globe- they pull the eye backwards

51
Q

In relation to rectus muscles, which direction do the obliques rotate the eye?

A

The opposite direction

52
Q

What effect does the superior rectus have on the eye?

A

It elevates the eye when in an abducted position

53
Q

What effect does the superior oblique have on the eye?

A

It depresses the eye when in an adducted position

54
Q

In 3rd nerve palsy what are the only two eye muscles that are working?

A

Lateral rectus and superior oblique

55
Q

What does this mean happens to the eye in 3rd nerve palsy?

A

The eye moves down and out

56
Q

What else do you get in 3rd nerve palsy?

A

Ptosis (drooping eyelid) because the oculomotor also innervates lid levator. There is also pupil dilation due to loss of parasympathetic innervation from oculomotor

57
Q

What muscle is no longer innervated in 6th nerve palsy?

A

Lateral rectus

58
Q

What does this means happens to the eye in 6th nerve palsy?

A

A deficit in abduction of the affected eye

59
Q

What is Hering’s law?

A

There is equal innate innervation to both muscles from both eyes involved in conjugate or pair movements

60
Q

What does the medial longitudinal fasciculatus do?

A

It acts as a link synchronising the 6th nerve nucleus on the right side and third nerve nucleus on left side so when the eyes looks to the left, both eyes move at the same time

61
Q

In what condition is Hering’s law violated?

A

Internuclear opthalmoplegia

62
Q

What is Sherrington’s law of reciprocal innervation?

A

Agonist muscles contract whilst antagonist muscles relax

63
Q

In what condition is Sherrington’s law violated?

A

Duane’s syndrome

64
Q

What is Duane’s syndrome?

A

Congenital absence of abducens- both medial and lateral rectus are innervated by oculomotor now so both agonist and antagonist contract at same time

LCRS Neuroscience (18 decks)

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