Visual Pathways/Oculomotor Flashcards by Shirley Yancey

Cone or rod?

Function optimally in light adaptations

Cone

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Cone or rod?

Mediate central and color vision

Cone

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Cone or rod?

Greatest density in fovea

Cone

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Greatest density of rods?

20 degrees from fovea

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Cone or rods?

More abundant in peripheral retina

Rods

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Cone or rods?

Function optimally in dark adaptation

Rods

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Axons from ganglion cells of nasal retina of each eye (cross/do not cross) in the ____

Cross

optic chiasm

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Nasal retina receives visual information from ____

temporal visual field

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Temporal retina receive visual information from ___

nasal visual field

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superior retina receives information from ____

inferior visual field

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Visual information pass through ____ from retinal ganglion cells to primary visual cortex

Lateral geniculate nucleus (LGN) of the thalamus

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Axons of ipsilateral retinal ganglion cells synapse in ___

layers 2, 3, 5 of lateral geniculate nucleus

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Axons of contralateral retinal ganglion cells synapse in ___

Layers 1, 4, 6 of lateral geniculate nucleus

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Magnocellular pathway are composed of layer ____ of LGN

Concerned with:

1 and 2

movement detection, detection of low contrast, dynamic form perception

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Parvocellular pathway composed of ___ layers of LGN

Concerned with:

3 and 6

Color selective and responsive to high contrast

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Most peripheral temporal visual field arises from (paired/unpaired) (crossed/uncrossed) axons from the (nasal/temporal) retina that projects to ____

Unpaired
Crossed
Nasal
Most anteromedial portion of visual cortex

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Macular disease produces ____

hemeralopia (day blindness)

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Peripheral retinal disease produces ____

Nyctalopia (night blindness)

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Diseases of optic nerve produces (3):

Central vision loss: decreased visual acuity w/ central scotoma
Impaired color vision
Impaired contrast vision

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Cardinal sign of optic nerve disease

Relative afferent pupillary defect: affected pupil will dilate when illuminated in swinging flashlight test

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Disease of optic chiasm produce:

Bitemporal hemianopia = temporal visual field defect

b/c only crossing fibers from nasal retina affected

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Disease affecting retrochiasmal visual pathway produces:

Homonymous hemianopia = visual field defect of same half of the visual field in bowth eyes

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Diseases affecting superior fibers produce:

homonymous inferior quadrantanopia = visual field defect of same inferior quarter of visual field in both eyes

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Ventral pathway of primary visual cortex is involved in:

Object identification and recognition

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dorsal pathway of primary visual cortex is involved in:

Visual information to aid in object localization in space

Prosopagnosia

Inability to recognize faces

Action of superior rectus

Elevation and intorsion

Action of inferior rectus

Depression and extorsion

Action of superior oblique

Depression and intorsion

Action of inferior oblique

Elevation and extorsion

CN3 nucleus located:

midbrain, ventral to cerebral aqueduct

Motor neurons for levator palpebrae superioris m. arise from:

central caudal nucleus (midline)

Motor neurons for superior rectus m. arise from:

CONTRALATERAL superior rectus subnucleus

Motor neurons for remaining extraocular m of CN3 arise from:

Ipsilateral subnuclei

CN4 nucleus located: | Motor neurons destined for superior oblique m. arise from:

dorsal-caudal midbrain | CONTRALATERAL CN4 nucleus

CN6 nucleus located in: | Contain motor neurons destined for (ipsi/contralateral) lateral rectus m.

Pontine tegmentum | Ipsilateral

3rd Nerve Palsy results in:

Impaired elevation, depression, adduction Inability to open eyes Dilated pupils

When looking straight ahead, pt with 3rd nerve palsy will have:

eye that deviates away from nose and downward (down and out)

Common causes of 3rd nerve palsy (2)

Microvascular ischemia | Compression by posterior communicating artery aneurysm

Compression by posterior communicating artery aneurysm will cause: Rule of pupil:

dilation of pupil b/c parasymp. fibers to sphincter m. are located peripherally and dorsally in nerve. Rule of the pupil: When CN3 is compressed by aneurysm, pupil wil dialate and/or sluggishly reactive.

Microvascular ischemia causing 3rd nerve palsy will affect:

Center of nerve, sparing pupil constriction

4th Nerve Palsy results in:

Impaired depression and intorsion of eye, especially when eye is adducted

Pt with 4th nerve palsy will tilt head to (ipsi/contralateral) side to compensate for impaired intorsion.

Contralateral

6th Nerve Palsy will result in:

impaired abduction of eye

Common cause of 6th nerve palsy

Alterations in intracranial pressure | Head trauma

Frontal eye fields located at: | Signals:

caudal end of middle frontal gyrus Contralateral voluntary saccades Contralateral smooth pursuts and vergence eye movements

Unilateral lesion of frontal eye fields will result in:

Ipsilateral gaze deviation | Loss of ability to produce contralateral voluntary saccades

Bilateral lesions of frontal eye fields will result in:

Ocular motor apraxia = Inability to produce voluntary saccades appropriately

Parietal eye fields located in: | Signals:

Lateral intraparietal sulcus Visual-evoked saccades Smooth pursuit

Omnipause neurons located in:

Nucleus raphe interpositus in pontine reticular formation

Constant stimulation of omnipause neurons result in:

inability to generate saccades

Neurons responsible for horizontal saccades are located in:

Pons in paramedian pontine reticular formation (PPRF)

Neurons responsible for vertical-torsional saccades are located in:

rostral midbrain in rostral interstitial nucleus of medial longitudinal fasciculus (riMLF)

Lesion of PPRF will result in:

Slowing/complete inability of ipsilateral horizontal saccades Gaze deviation to contralateral side Ipsilateral facial palsy Horizontal VOR remains intact

Lesion of MLF will result in:

Slowing/complete inability to adduct ipsilateral eye during contralateral saccades

Bilateral lesion of riMLF will:

abolish all vertical saccadic eye movements Vertical VOR remains intact

Horizontal component of step signal produced by:

medial vestibular nuclei | nucleus prepositus hypoglossi

Vertical and torsional component of step signal produced by:

Interstitial nucleus of Cajal in midbrain reticular formation

Lesions of neural integrator will produce:

Gaze-evoked nystagmus: Drift of eye back to center that's corrected for by saccadic eye movements back to object of interest

Instability of neural integrator results in:

Pendular nystagmus = eye oscillations

Lesion in interstitial nucleus of Cajal will result in:

Seesaw nystagmus = vertical and torsional oscillations

Near response triad

1. Convergence of eyes 2. Accommodation of lens 3. Constriction of pupil (miosis)