Visual Pathways/Oculomotor Flashcards
Cone or rod?
Function optimally in light adaptations
Cone
Cone or rod?
Mediate central and color vision
Cone
Cone or rod?
Greatest density in fovea
Cone
Greatest density of rods?
20 degrees from fovea
Cone or rods?
More abundant in peripheral retina
Rods
Cone or rods?
Function optimally in dark adaptation
Rods
Axons from ganglion cells of nasal retina of each eye (cross/do not cross) in the ____
Cross
optic chiasm
Nasal retina receives visual information from ____
temporal visual field
Temporal retina receive visual information from ___
nasal visual field
superior retina receives information from ____
inferior visual field
Visual information pass through ____ from retinal ganglion cells to primary visual cortex
Lateral geniculate nucleus (LGN) of the thalamus
Axons of ipsilateral retinal ganglion cells synapse in ___
layers 2, 3, 5 of lateral geniculate nucleus
Axons of contralateral retinal ganglion cells synapse in ___
Layers 1, 4, 6 of lateral geniculate nucleus
Magnocellular pathway are composed of layer ____ of LGN
Concerned with:
1 and 2
movement detection, detection of low contrast, dynamic form perception
Parvocellular pathway composed of ___ layers of LGN
Concerned with:
3 and 6
Color selective and responsive to high contrast
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
Macular disease produces ____
hemeralopia (day blindness)
Peripheral retinal disease produces ____
Nyctalopia (night blindness)
Diseases of optic nerve produces (3):
Central vision loss: decreased visual acuity w/ central scotoma
Impaired color vision
Impaired contrast vision
Cardinal sign of optic nerve disease
Relative afferent pupillary defect: affected pupil will dilate when illuminated in swinging flashlight test
Disease of optic chiasm produce:
Bitemporal hemianopia = temporal visual field defect
b/c only crossing fibers from nasal retina affected
Disease affecting retrochiasmal visual pathway produces:
Homonymous hemianopia = visual field defect of same half of the visual field in bowth eyes
Diseases affecting superior fibers produce:
homonymous inferior quadrantanopia = visual field defect of same inferior quarter of visual field in both eyes
Ventral pathway of primary visual cortex is involved in:
Object identification and recognition
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
- Convergence of eyes
- Accommodation of lens
- Constriction of pupil (miosis)