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Neuroanatomy > Vision > Flashcards

Vision Flashcards

1
Q

What are the extraoccular muscles?

A

Muscles involved in eyemovement; Lateral Rectus (6); Superior Oblique (4); superior rectus, medial rectus, inferior rectus; inferior oblique (3)

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2
Q

Which extraoccular muscles are innervated by the Abducens nerve?

A

lateral rectus

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3
Q

Which extraocculuar muscle is innervated by the Trochlear nerve?

A

Superior oblique

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4
Q

Which extraoccular muscles are innervated by CN III

A

superior rectus, medial rectus, inferior rectus, inferior oblique

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5
Q

Which fibre bundle is associated with communication between motor CN nuclei involved in gaze?

A

Medial longitudinal fasciculus

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6
Q

Where is the MLF at the level of the rostral pons?

A
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7
Q

Where is the MLF at the level of the caudal pons?

A
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8
Q

Where is the MLF at the level of the midbrain?

A
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9
Q

Where is the vertical gaze centre?

A

Midbrain - reticular formation and pretectal area

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10
Q

Where is the horizontal gaze centre?

A

Pons - paramedian pontine RF (PPRF)

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11
Q

How many neurons are involved in directing the gaze to the right

A

4 - 1) the horizontal gaze centre neurons synpapse on the abducens nucleus; IPSI CN VI terminates on the right lateral rectus (LR6); 3) another set of abducens neurons cross the midline and synapse at the OCCULOMOTOR nucleus; 4) occulomotor neurons innervate the ipsilateral medial rectus

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12
Q

What would happen to gaze if there was a lesion to the RIGHT abducens nerve

A

Ipsilateral (right) eye would fail to abduct when looking to the right; leftward gaze would be unaffected

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13
Q

What is a reflexive saccade?

A

Visually guided saccade in response to external cue (prosaccade)

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14
Q

What is a volitional saccade

A

voluntary eye movement

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15
Q

What is the main input for voilutional saccades?

A

Frontal eye fields in SMA (BA 8)

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16
Q

What is the main input for reflexive saccades

A

Superior colliculi (brainstem)

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17
Q

Reflexive saccades recruit which structures?

A

Frontal eye fields –> ipsi superior colliculus –> contralateral horizontal gaze centre –> abducens nucleus –> ipsi lateral rectus and contra occulomotor nucleus –> ipsi left medial rectus

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18
Q

What is found in the DESCENDING MLF?

A

Medial and lateral vestibulospinal tracts

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19
Q

Which structures are involve in smooth pursuit?

A

FEF and V1 –> ipsilateral pontine nuclei (cerebropontine) –> contralateral cerebellum –> ipsilateral vestibular nuclei –> contralateral abducens nucleus –> activation of ips CNVI and contra CN III via the MLF

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20
Q

Which direction do eyes move in the VOR

A

Opposite of the direction of head movement

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21
Q

Which structures are involved in the VOR response to leftward head rotation?

A

1) Left horizontal canal —> ipsi vestibular nuclei —> contra abducens nucleus —> ipsi CN VI and contra CN III via MLF and occulomotor nucleus

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22
Q

Which muscles are involved in the pupillary reflex?

A

Constrictor pupillae

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23
Q

Which nuclei are involved in pupillary constriction

A

1) Pretectal; 2) Edinger-Westphal (CN-III GVE)

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24
Q

What are the first step involved in pupillary constriction?

A

1) light reaches retina; info travels to pre-tectal nuclei in midbrain via optic nerve and optic tract (post-chiasm)

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25
Q

What is the role of the pretectal nuclei in pupillary constriction?

A

Send bilateral projections to the edinger-westphal nuclei of CN III

26
Q

What is the role of the edinger-westphal nuclei in pupillary constriction

A

Send preganglionic efferents (GVEs) to the ciliary ganglia

27
Q

What happens at ciliary ganglia during pupil constriction?

A

Receive pre-ganglionic input from edinger-westphal nucleus; send post-ganglionic projections (ciliary nerves) to innervate constrictor pupillae muscles

28
Q

If parasympathetic fibres in the right CN III were damaged, what would happen when a light was shone into the right eye?

A

No pupillary constriction in right eye BUT left eye will still constrict; called “blown pupil”

29
Q

Which fibres cross the optic nerve?

A

Fibres from the NASAL (medial) half of each retina

30
Q

Which tract do fibres travel in on their way from the LGN to V1?

A

Optic radiation (geniculocalcarine tract)

31
Q

Which fibres form Meyer’s loop?

A

More ventral fibres (representing info from the upper visual field)

32
Q

Where do tracts from the upper and lower visual field end up in the cortex

A

Lower portion of calcarine sulcus (upper); upper portion of calcarine sulcus (lower)

33
Q

Which portion of the visual field travels via Meyer’s loop upon exiting the LGN?

A

Upper visual field (“bottom” of the retina)

34
Q

What is a homonymous visual field deficit?

A

One that affects both eyes in the same part of the visual field

35
Q

Monocular vision loss is due to a lesion to ____

A

Optic nerve

36
Q

A lesion to the optic chiasm causes ____

A

Loss of temporal vision in both visual fields – bitemporal hemianopia

37
Q

A lesion to the optic tract causes ____

A

Loss of the contralateral visual field in BOTH eyes

38
Q

A lesion to Meyer loop causes ____

A

Upper portion of the contralateral visual field in both eyes

39
Q

A partial lesion to the optic radiations before they are joined by fibres from Meyer’s loop ___

A

Loss of lower portion of contralateral visual field in both eyes

40
Q

A lesion of the entire V1 ___

A

Loss of the contralateral visual field on both sides

41
Q

Pupillodilator reflex begins where with which type of stimulus

A

Lateral horn neurons in T1 receive descending input (from e.g., the hypothalamus) in response to EMOTIONAL cues

42
Q

Where do preganglionic fibres travel after receiving descening input for the pupillodilator reflex

A

Leave SC; travel up sympathetic trunk to superior cervical ganglion

43
Q

Where do postganglionic neurons from the superior cervical ganglion go to intiate the pupillodilator reflex?

A

Travel along internal carotid and via the opthalmic division of CN V

44
Q

Which nerves innervate the dilator pupillae muscles

A

Long cilliary nerves (branch off of CN V-1 opthalmic)

45
Q

The corneal blink reflex is mediate by WHICH cranial nerve afferent

A

Trigeminal (V)

46
Q

Which brainstem nuclei are involved in the corneal nerve reflex

A

Trigeminal Sensory nucleus and facial motor nucleus

47
Q

Which muscle do fibres from the facial motor nucleus innervate to cause the blinking reflex

A

Orbicularis oculi

48
Q

Convergence of the eyes (close vengence point) involves WHICH muscles and associated motor nuclei?

A

Medial rectus; oculomotor nuclei

49
Q

Divergence of the eyes (far vengence point) requires WHICH muscles and assocaited motor nuclei

A

lateral rectus (abducens)

50
Q

Which area of the rostral midbrain is responsible for coordinating the accommodation reflex

A

Supraocculomotor Area

51
Q

Which processes occur during accomodation?

A

1) Convergence, 2) Pupillary constriction 3) Thickening of the lens

52
Q

Which brainstem nuclie does the supraocculomotor area activate to intiate accomodation

A

1) Oculomotor (activates the medial rectus muscles) 2) Edinger-westphal nucleus (para efferents innervate the ciliary ganglion)

53
Q

Afferent component of the pupillary light reflex

A

retinal info to pretectal area; pretectal to EW nucleus

54
Q

Efferent component of pupillary light reflex

A

CN III (occulomotor nerve) –> ciliarly ganglion –> ciliary nerves –> iris constrictor muscles

55
Q

Afferent component of ACCOMODATION

A

retina (receptors and neuronal elements), optic nerves, optic chiasm, optic tracts, lateral geniculate bodies, geniculocalcarine tracts, visual cortex. Corticotectal projections to superior colliculus/pretectal area - then to oculomotor nuclear complex.

56
Q

Accomodation efferent component

A

CNIII nerve, ciliary ganglion, short ciliary nerves, ciliary muscle andconstrictor.•CNIII nerve, medial rectus muscle.

57
Q

Pupilodilator reflex afferent component

A

Afferent component - from posterior hypothalamus via brainstem. Reticular formation to preganglionic sympathetic neurons at C8 and T1. Information via sympathetic trunk to superior cervical ganglion.

58
Q

Pupilodilator reflex efferent component

A

Efferent component - postganglionic sympathetic fibers via nasociliary nerve (travels in opthalmic division of V-1), which gives off long ciliary nerves to dilator muscle of iris.

59
Q

Where are the trochlear (CN IV) nuclei

A

Caudal midbrain; anterior part of PAG

60
Q

What is in the DESCENDING MLF

A

Vestibulospinal tract

61
Q

What is in the ASCENDING MLF

A

Connects CN-IV with CN-III; also connect VIII (vestibular) to CN III, IV, and VI for the VOR

62
Q
A

Neuroanatomy (13 decks)

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