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Veterinary Neurology > Vision > Flashcards

Vision Flashcards

1
Q

Optic tract brings axons to three targets: lateral geniculate nucleus (LGN), pretectal nucleus, rostral colliculus.

A

Cortical projections in the LGN
optic tract->LGN->VI (primary visual cortex)
optic tract->LGN->brachium of rostral colliculus->rostral colliculus and pretectal area

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2
Q

Direct light reflex

A

Pupil constriction in illuminated eye

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3
Q

Nyastagmus

A

Periodic back and forth or up and down eye movement
Vestibular (prolonged angular acceleration of head) or Opticokinetic (passage of series of objects through the visual fields)

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4
Q

Eye movement control

A

Motorneurons to extra ocular eye muscles (3, 4, 6)
Gaze centers of brainstem (movement horizontal and vertical)
Cortex and brainstem (initiate particular types of movements)

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5
Q

Eye movements

A

Maintain visual fixation on a visual target already in view and reorient eyes toward a new target

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6
Q

Retino-tectal system

A

Characterized as reflex visuomotor system, controlling such reflex unconscious activities as pupillary dilation and constriction, head and eye orientation to visual stimuli
Axons pass directly to pretectum and rostral colliculus without synapsing in lateral geniculate body

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7
Q

Lateral geniculate nucleus (LGN)

A

Visual cortex for form vision (discriminative: what, where, color, motion)

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8
Q

Retinal field

A

Retinal area upon which light falls

Light that originates in temporal visual field strikes the nasal retinal field

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9
Q

Optic tract brings axons to:

A

Lateral geniculate nucleus (LGN), pretectal nucleus, and rostral colliculus

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10
Q

Horizontal gaze center

A

PPRF, activation leads to conjugate gaze shifts toward ipsilateral side
MLF interconnects motor nuclei of CN III and VI, coordinates horizontal conjugate eye movements

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11
Q

Visual field

A

Location in space from which light originates

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12
Q

Rounding of lens

A

Contraction of ciliary muscle to relax tension on lens, allowing it to round and increase optical power -> focuses eye on near object

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13
Q

Constriction of pupil

A

Improvement of visions through limiting entrance of stray light

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14
Q

Reflex orienting of the eyes

A

tecto-oculomotor system, CN III nucleus, CN IV nucleus, N VI nucleus

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15
Q

Tecto-oculomotor system

A

Rostral colliculus exercises control over eye movement

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16
Q

Convergence of eyes

A

Co-contraction of medial rectus muscles to align eyes with near object

17
Q

Startle and orienting of head and neck

A

Tectospinal tract, cervical spinal cord motorneurons

18
Q

Tectospinal tract

A

Originates from rostral colliculus
Descends with medal longitudinal fasiculus (MLF)
Subserves head reflex and upper extremity movement to photic stimuli

19
Q

Conjugate gaze and pursuit

A

Frontal eye fields and parietal-occipital cortex, paramedic pontine reticular formation (PPRF), MLF, motor nuclei of III and VI

20
Q

Pretectal nucleus

A

Pupillary light reflexes

21
Q

Acuity

A

Minimum size of visual targets that can be detected

22
Q

Fovea

A

Center of macula, area of pure cones

23
Q

Macula

A

Location of majority of the cones where visual is normally centered

24
Q

Rostral colliculus

A

Visual orienting response via tectospinal tract

25
Q

Consensual reflex

A

Pupil constriction upon illumination of the other eye, mediated by caudal commissure which connects the two pretectal nuclei

26
Q

Convergence

A

CN III nucleus, medial rectus muscles

27
Q

Near triad

A

Accomplishment of focused vision upon attention to a near object, 3 integrated motor elements

28
Q

Accommodation

A

Optic tract, pretectal nucleus, Ed West nucleus, ciliary ganglion, ciliary muscle
Postganglionic fibers from ciliary ganglion terminate in ciliary muscle (allow lens to round and focus eye near vision)

29
Q

Decrease pupil size

A

Caused by postganlionic fibers from ciliary ganglion terminating in sphincter muscle of iris

30
Q

Pupillary Light Reflexes

A

Optic tract, pretectal nucleus, Ed West nucleus, ciliary ganglion, pupil

31
Q

Pretectal nuclei

A

Right and left connected by caudal commissure, output pathways go to both ipsilateral and contralateral Edinger-Westphal nuclei (PS portion of CN III)

Veterinary Neurology (9 decks)

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