Visual System Flashcards
Rectus Muscles
Superior: elevation
Inferior: Depression
Medial: look in
Lateral: look out (Abducens)
Oblique Muscles
-Superior (Trochlear)
-Inferior (Oculomotor)
Pupillary Light Reflex
-Afferent: Optic
Efferent: Oculomotor
-consensual light response
Eye Anatomy
Sclera and Cornea: most anterior
Pupil: controls light into eye
Lens: accommodates for near objects
Choroid: Superficial Layer of blood vessels
Retina: Innermost layer with neurons (rods and cones)
Fovea: in retina, highest visual acuity with smallest field; only cones
Optic Disc: blind spot
Vitreous Humor: jelly substance
Retina
Outer Layer: melain to decrease light scattering
Inner Layer: phototransduction site
-Photreceptors: Rods (b/w) and Cones (color)
-Bipolar cells: transfer info to ganglion cells
-Ganglion Cells: generate AP as 1st order neuron and synapse with optic nerve
Phototransduction
-release of neurotransmitter by photoreceptors generate AP in ganglion cells (1st order)
-Cones: color, low light sensitivity, small receptive field
-Rods: black and white, large receptive field, high light sensitity, more abundant
Visual Perception
-Ganglion cells (1st order) < optic N. < optic chiasm < optic tract < (2nd order) lateral geniculate body in thalamus < Optic radiation < Primary visual cortex
-imiage is inverted and reversed
Optic Nerve
-ipsilateral nasal (inner fibers) and temporal fibers (outer fibers)
Lesion: ipsi eye blindness
Optic Chiasm
-nasal fibers cross here (inner fibers)
-Temportal fibers stay ipsi
Lesion:
-only temporal fibers
-Bitemporal hemianopsia
- Outer field of vision gone in B eyes
-LE L field gone, RE R field gone
Optic Tract
-Ipsi temporal fibers
-contra nasal fibers
-hemi-visual field
Lesion:
-Homonymous hemianopsia
-contra side of lesion gone in same half of vision in both eyes
- Right lesion, LE L field gone, RE L field Gone
Primary Visual Cortex
Cuneus: upper bank; lower quadrant of both eyes
Lingua: lower bank; upper quadrant of both eyes
Visual Association cortex:
-Dorsal Stream: parieto-occippital cortex; motion; localization
-Ventral Stream: occipito-temporal cortex; perception, high resolution and visual acuity, recognition
Eye Movement
Functions
Stabilize Gaze: eye stable during head mmt
-Vestibulo-Ocular Reflex: stabilize images during slow head mmt; eyes stable with head turn in opposite direction to keep stable on retina
-Optokinetic Reflex: vestib info on eye position during head mmt; quick saccades to keep target in eye sight
Movements
-Conjugate: both eyes move in the same direction; both looking right
-Vergence: both eyes move in diff; Convergence (crossing); Divergence (away from midline)
-Saccades: rapid eye mmt to scan, read; align fovea with scene
-Smooth Pursuit: slow tracking mmt of eyes
Eye Movement Control: Brain Stem
-Pontine reticular formation (horizontal gaze center)
-Rostral inttersistial Nuc in RF (vertical gaze center)
-Medial longitudinal fasciculus (coordinates both neural circuits)
-CNs
-Vestib N
Eye Movement Control: Forebrain
-initiates accurately shiftitng eyes toward target
Frontal eye field: contra saccades and smooth pursuit
Parieto-Occipital-temporal complex: ipsi smooth pursuit
Superior Colliculus: optic tectum, attention and acuracy of eye mmt in response
Eye Movement Control: Basal Ganglia
-initiation of eye mmt
-oculomotor loop
-prefrontal loop
