Visual System Flashcards
where does the majority of refraction / bending of light occur in the eye?
the cornea
vitreous body function
a gel (high in hyaluronic acid) that gives shape to the eye
the retina comes from where?
the retina is an outgrowth of the brain from the diencephalon
what is the only cell type that sends axons out of the eye?
retinal ganglion cells
where are the retinal ganglion cells located?
in the inner surface of the retina
where is light converted into chemical energy?
in the rods and cones
are the axons myelinated in the eye?
axons are NOT myelinated in the eye b/c myelin can scatter light
describe the area surrounding the fovea
there is a physical removal of all things surrounding the fovea. Ie no vasculature
cones function
high acuity vision
color
rods function
peripheral vision
black and white and night vision
optic disc
“blind spot” this is where the blood vessels enter and exit as well as the optic nerve exits here
what is the name of the surface of the retina that is on the medial surface (towards the nose) that looks out laterally?
temporal visual field
what is the name of the surface of the retina that is on the lateral surface that looks in medially towards the nose?
nasal visual field
what axons of the optic nerve decussate
the temporal visual field axons
the left optic tract carries vision from where?
look what direction(s)
- the left eye’s nasal visual field and the right eye’s temporal visual field
- thus it looks right
the right optic tract carries vision from where?
look what direction(s)
the left eye’s temporal visual field and the right eye’s nasal visual field
-look left
what can pituitary tumors cause?
bitemporal vision loss = can see peripheral vision
how do the axons of the optic tract get primary visual cortex?
synapse in the lateral geniculate nucleus (of the thalamus) and take the optic radiations back to the occipital lobe
the temporal lobe carriers vision for what area?
the temporal lobe (bottom of the brain) carries vison for the sky
the parietal lobe carriers vision for what area?
the parietal lobe (top of the brain) carries vision for the ground
where is the primary visual cortex located?
- the occipital lobe (calcarine cortex)
- medial surface of the cortex
the upper cyrus carries vision for the _______
ground
the lower gyrus carries vision for the _______
sky
the posterior cerebral artery supplies the _______
calcarine cortex (primary visual field) - occipital lobe and the temporal lobe
the ophthalmic artery supplies the _______
retina, eye, optic nerve
the middle cerebral artery supplies the _______
parietal cortex, optic radiations
the anterior choroidal artery supplies the _________
optic tract, lateral geniculate nucleus, thalamus
macular vision receives blood from ________
both the posterior cerebral artery and the middle cerebral artery
what happens if you cut the right optic nerve?
blind in right eye
what happens if you cut the optic chiasm? what is this called?
bitemporal hemianopia = no peripheral vision
what happens if you cut the right optic tract? what is this called?
left homonymous hemianopia = can’t see left field of vision
what hoes anopia mean?
loss of vision
what happens if you cut both left upper and lower optic radiations? what is it called?
right homonymous hemianopia = loss of right field of vision
what happens if you cut the left lower optic radiation? what is it called?
right superior quadrantopia = can’t see upper right field of vision
what happens if you cut the left upper optic radiation? what is it called?
right inferior quadrantopia = cant see lower right field of vison
in regards to the pupillary light reflex, if there is a lesion in CN II of the left eye, what happens when a light is shined in the left eye? What about the right?
light shined in the left eye - nothing happens in both eyes.
Light shined in right eye - both eyes pupils constrict
what is double vision called and when does it occur?
diplopia = double vison
-occurs when convergence doesn’t happen
describe the near response
input?
output?
input- CN II to lateral geniculate
output- 1. CN III - medial rectus
2. CN III - ciliary ganglion - pupillary constrictors
what happens to the near response in the right oculomotor lesion?
- right pupil is dilated
- pupillary light reflex absent in right eye
- near response absent in the right eye
- ptosis in right eye
what controls pupillary dilation
sympathetic nervous system = hypothalamus
what is the sympathetic pathway to dilate the eye?
hypothalamus to T1 to superior cervical ganglion to dilator pupilae
what causes Horner’s syndrome? Symptoms?
a lesion anywhere in the central or peripheral sympathetic nervous pathway
P- ptosis = droopy eyelid
A- anhydrosis
M- miosis - constricted pupil
what are some affects a subdural hematoma can have?
temporal lobe can squeeze the midbrain (small ventricles, misshapen peduncles, compressed midbrain)
-causing problems with CN 3 (pupillary light reflex), ptosis, problems with the cerebral peduncles (hyperreflexia, weakness, upper motor neuron damage)
the left frontal eye field moves the eyes _________
to the right = contralateral
a damaged right frontal field of cortex would cause the eye to move where?
to the right
a seizure can cause the field of frontal cortex to move to where?
to the contralateral side
what are the two most important cranial nerves of the eye to more in horizontal direction?
CN III - medial rectus of one eye works at the same time as the lateral rectus of the other eye (CN VI)
PPRF
paramedian pontine reticular formation
where is the PPRF located?
nucleus is located in the pons
what does the PPRF control
horizontal eye movements
the left cortex make your look _____
right
what connects the PPRF to CN III
the medial longitudinal fascicules (MLF)
what would happen if there was a problem with the right medial longitudinal Fascicules (MLF)?
- can not adduct right eye when both eyes are trying to look left
- medial rectus works fine just not when both eyes are engaged
- all other CN III functions are ok
in reference to the abducens nucleus, where is the paramedian pontine reticular formation located?
-rostral and ventral to the abducens nucleus
cells in the frontal eye field project to the _________ PPRF
contralateral
