Chapter 14 Flashcards
(24 cards)
How is glaucoma different from cataract?
glaucoma - result of intraocular pressure causing damage to retinal & optic nerve.
cataract - results from opacification of the lens causing impaired vision b interfering with light rays passing though it.
Between what layers does the detachment of the retina occur?
between layer 1 - pigment layer
and layer 2 - photoreceptor layer (rods & cones)
*the detached part ceases to function b/c the rods and cones are metabolically dependent on the pigment cells.
What morphologic features are common to retinal layers 4, 6, and 8?
they all contain cell bodies:
layer 4 - photoreceptors cell bodies (rods & cones)
layer 6 - bipolar neuron
layer 8 - ganglion cells
Night blindness is associated with functional deficits in what structures? What vitamin would be involved?
result from vitamin A deficiency which aids in the restoration of the photopigment rhodopsin in the rods.
Color blindness is associated with functional deficits in what structures?
associated with the absence of red-, green-, and blue- sensitive pigments in the cones.
Compare the fovea centralis and optic disc as to morphology and function?
fovea centralis - most acute vision, cons, only layers 1,2,3,4 and 10.
optic disc - where ganglion cell axons gather together and emerge forming the optic nerve, only layers 9 and 10 and is the blind spot b/c there is no photoreceptors.
What is the medical significance of the morphologic features unique to the optic nerve?
- possess CNS morphologic characteristics
- resembles spinal cord/brainstem tract b/c its axons are supported by glial cells, no neurolemma cells, so they do not regenerate if injured.
- medically important, optic nerve enveloped by the meninges and cerebralspinal fluid in the subarachnoid space can put pressure on the nerve causing edematous selling of the optic disc termed disc edema, papilledema, or chocked disc.
How is transduction of sensory stills in the retina different from transduction in most other sensory systems?
in retina - a photon of night hitting retina triggers a biochemical change in the visual pigments (rhodopsin & iodopsin)
somatosensory - a mechanical stimulus alters receptor membran potential resulting in ionic conductance.
How is processing a visual stimuli different in the retina and lateral geniculate nucleus compared with the primary visual cortex?
retina and lateral geniculate - respond to focused spots of light with “on-center or off-center” response properties.
primary visual cortex - neurons transform this input to lines of bars of different orientations
The conscious interpretation of shape, motion, and color course in what area(s) of the cerebral cortex?
cortical areas away from primary visual cortex - shape, color, movement.
inferior temporal cortex - shape and color
posterior parietal cortex - movement
A patient with homonymous hemianopia and absence of the direct and consensual pupillary light reflexes upon shining a small pin-point beam of light onto only the blind half of either retina has a lesion in the?
c: optic tract
Visual field deficits accompanied by light reflexes deficits can only occur with damage of the visual pathways between?
between the retina and the lateral geniculate nucleus (optic nerve, chasm or tract)
A lesion in the visual path distal to the optic tract will result in what?
- lesions distal to optic tract could involve the lateral geniculate nucleus, optic radiation, or visual cortex.
- will spare the pupillary light reflex fibers that bypass the lateral geniculate nucleus in the brachium of the superior colliculus.
A patient presents with a history of gradual loss of visual sensations from only a limited area of the visual field. Temporally staggered neuroimagining reveals a slowly enlarging mass in the right temporal lobe white matter. This probable tumor is likely damaging?
c: right loop of Meyer
The visual deficit caused by the tumor/lesion in the right loop of Meyer will result in?
a: left homonynmous superior quadratic anopsia
A patient awakens with sensory and motor abnormalities involving the left side of the body and face and an impairment of vision of the left field of vision. Examination reveals a left hemianesthesia, left spastic hemiplegia, and left homonymous hemianopsia. The most likely location for a lesion(s) causing these deficits would be?
d: single lesion in the right posterior limb of the internal capsule
A stroke in the right parietal lobe may result in?
a: left homonymous lower quadratic anopsia
A pituitary tumor that bisects the optic chasm causes damage to the optic nerve fibers arising from the?
b: left and right nasal retinae
* retinogeniculate projections rom the nasal retinae transmit input from the temporal visual fields and dessert in the optic chiasm.
What visual field deficits result from destructive lesions in the left optic nerve?
blindness in left eye
What visual field deficits result from destructive lesions in the median part of optic chiasm?
bitemporal hemianopsia
What visual field deficits result from destructive lesions in the retrolenticular part of right internal capsule?
left homonymous hemianopsia
What visual field deficits result from destructive lesions in the right striate cortex?
left homonymous hemianopsia
What visual field deficits result from destructive lesions in the right angle of chiasm?
right nasal hemianopsia
What visual field deficits result from destructive lesions in the right optic tract?
left homonymous hemianopsia
