The visual system Flashcards
what are the only cells in the retina that produce nerve impulses?
retinal ganglion cells(projection neurons)
what are the only cells that have projections that leave the eye?
retinal ganglion cells(projection neurons)
what neurons process light?
internal nuclear cell layer
what do amacrine cells and horizontal cells do?
talk with multiple streams of information and provide contrast in the visual field.
eg: being able to detect edges
what do rods and cones do?
phototransduction, grated potentials
what cell spans the retina and provides ion support and makes the virtuous humor? It is the only glial cell as well
muller supporting cell
what cells are the only cells that us an action potential in the retina?
the retinal ganglion cells the rest use graded potentials
what is the fovea used for?
high acuity vision, highest amount of cones are here
where are rods located?
just outside the fovea
what happens are the chiasm?
a partial decussation
axons for temporal visual fields (lateral) do what at chiasm?
cross the contralateral
axons for the nasal visual vision (medial) do what at chiasm?
remain ipsilateral
the optic tract projects to what struction in the thalamus?
lateral geniculate nucleus (LGN)
secondary neurons from the lateral geniculate nucleus go where?
to the primary visual cortex via optic radiations
where is the superior field of vision located in the optic radiations?
in the temporal portion called the meyes loop
where is the inferior field of vision located in the optic radiations?
in the parietal part
what does pie in the sky mean?
damage to meyers loop will result in losing the superior vision
primary visual cortex is divided into two portions, what are they?
lower field which is above the upper field
what is the macula?
where high acuity vision goes
what is the calcarine sulcus
what divides the lower and upper fields gyrus in the primary visual cortex
the retinal is supplied by what artery?
ophthalmic artery
the optic tract and lateral geniculate nucleus is supplied by what artery?
anterior choroidal artery(branch of middle cerebral)
what parietal optic radiations are supplied by what artery?
middle cerebral
the calcarine cortex is supplied by what artery?
posterior cerebral artery from the basilar artery
in the pupillary light reflex the retinal ganglion cells send axons to what nucleus?
pretectal region
axons from the pretectal region nucleus go where?
to the EW nucleus
from the EW nucleus where do the parasympathetic axons go?
to the ciliary ganglion
the nerve axons from the ciliary ganglion then go where?
to the pupillary constrictor muscles
is the pupillary light reflex consensual?
yes
subdural hematoma with uncal herniation symptoms
sluggish or absent pupillary reflex
ptosis
less effects on extraocular movements
CNIII effects
pupillary dilation sympathetic pathway 1st step
hypothalamus sends signal to T1 sympathetics
from the T1 level where does the sympathetic axon go?
to the superior cervical ganglion
from the superior cervical ganglion where do the axons go?
to the pupil
tarsal muscle
symptoms of horner’s syndrom
ptosis
miosis
anhyrosis
PAM has horns
a lesion any where on the sympathetic pathway will lead to horner’s syndrome T/F?
true
what does it mean that eyes are yoked?
move the same direction
controlled by centers in cortex and brainstem
no direct path from upper motor neurons to cranial nerves
frontal eye fields do what?
voluntary fast horizontal eye movements of the opposite eye.
what is the PPRF?
paramedian pontine reticular formation
cells in the frontal eye field project to contralateral PPRF T/F
true
where does the crossing occur ?
cuadal to nucleus III
what does the PPRF do?
coordiates horizontal movements between CN III, IV, VI for both eyes
from the PPRF where do axons go?
to the CN VI nucleus
from CN VI where do the axons go?
to the lateral rectus and to CN III nucleus
when axons from CN VI go the CN III nucleus what does it do?
synapses only on the medial rectus neurons
PPRF lesions lead to horizontal gaze paralysis of both eyes, toward the side of the lesion or to the opposite side of lesion?
to the same side
what is the MLF
the neuron going from CN VI nucleus to CN III nucleus
a lesion of the MLF leads to what?
loss of adduction in ipsilateral eye.
diplopia(double vision)
typically a sign of MS
*other CN III functions are unaffected
