visual pathways Flashcards
visual system pathway components
- temporal and nasal retina
- optic nerve
- optic chiasm
- optic tract
- pulvinar nucleus
- lateral geniculate body
- superior colliculus
- optic radiation
- primary visual cortex
retina components
- rods
- cones
- ganglion cells (optic disc)
rods
- dim light and peripheral vision
- rhadapsin inhibits glutamate which is continuously secreted in darkness
compenents of rods
- inner
- outer (~700 discs with rhadapsin)
- rod fiber (nucleus)
cones
- 3 types (red, blue, yellow)
- visual acuity and trichromatic vision
components of cones
- inner
- outer (pigment-bearing discs)
retinal cells
- midget cells
- parasol cells
- association neurons
- muller glial cells
where are neural signals from the rods and cones processed
in retinal ganglion cells in the posterior retina
midget cells
- small dendritic arbors
- small slow-moving stimuli
- not sensitive to low contrast
- color
parasol cells
- large dendritic arbors
- large fast moving stimuli
- sensitive to low contrast
- no color
association neurons
- amacrine cells (inhibit and excite)
- horizontal cells (inhibit)
- interplexiform cells (feeback between amacrine and horizontal cells)
muller glial cells
support
pathway to the visual cortex
- optic nerve to optic chiasm (hypothalamus)
- visual fields cross to lateral geniculate nucleus of the thalamus
optic nerve portions
- intraocular portion
- intraorbital portion
- intra-canalicular portion
- intracranial portion
optic tract/chiasm location
superior to sella turcica and pituitary gland
what are the optic tract/chiasm susceptible to
secondary pituitary disorders
pulvinar nucleus
- largest thalamic nucleus
- medial and dorsal to the lateral geniculate nucleus
most fibers travel from the chiasm after splitting to lateral geniculate nucleus but 10% travel to …
superior colliculus and pulvinar nucleus to the primary visual cortex
which retinal cells input info to the lower geniculate nucleus
- midget ganglion cells
- pasasol cells
optic radiations
- geniculocalcarine fibers
- exit dorsally from lower geniculate nucleus then spread into superior and inferior bundles
dorsal and central optic radiations travel in ? to ?
parietal lobe; visual cortex
ventral optic radiations curve in an anteroinferior direction into the ?
anterior pole of temporal lobe
meyers loop
ventral group of optic radiation fibers
optic radiation function
carry information from the thalamus’s lower geniculate neuron to the primary visual cortex
what information is processed in the primary cortex
- static versus moving objects
- pattern recognition
what information is processed in occipital, parietal, temporal lobe
- object recognition
- color perception
- depth
- motion
primary visual area brodmanns area
17
secondary visual area brodmanns areas
18, 19
visual defects
- retinal detachment
- color vision deficiency
retinal detachment
- blow to the eye
- fluid accumulation
- can lead to blindness
color vision deficiency
- dichromatic vision (one opsin not produced)
- monochromatic vision (2/3 cone opsin not produced)
4 common neurological patterns of vision loss
- monocular blindness
- bitemporal hemianopia
- homonymous hemianopia
- lesions of the primary visual cortex
monocular blindness
- lesion at optic nerve
- stroke (ophthalmic artery)
- migraine (transient)
- MS (bilateral)
bitemporal hemianopia
- optic nerve compression
- pituitary tumor
- info from temporal visual field falls on the nasal retina
- vision is missing in the outer half of left and right visual fields
homonymous hemianopia
- posterior cerebral artery stroke
- lesion after optic chiasm
- vertical midline loss
lesions of the primary visual cortex
- scotoma
- hole is the visual field
