Visual Pathway Flashcards
what does the choroid layer do?
provide nourishment
macula is rich in what
cone cells
why are there so many cell layers in the retina
reduce intensity of the light
how many layer groups in the retina
two - neuronal and non-neuronal
what do bipolar cells connect
photoreceptors to the ganglion cells
what do ganglion cells do
give off an axon that goes on to become the optic nerve
positioning of optic disc relative to fovea
slightly medial
what type of cells make up first order neuron
bipolar cells
what type of cells make up second order neuron
ganglion cells
where are first and second neurons located?
in the retina
are eyes in PNS or CNS?
ALL CNS
Outgrowth of diencephalon
path of ganglion cells
run over retina to optic disk/blind spot
forms optic nerve
optic nerve runs to LGN (thalamus)
third order neuron nerve path
LGN in thalamus via optic radiation to primary visual cortex
as an outgrowth of the diencephalon it has…
meninges
optic nerves pass out through which foramen
optic canal
the dura forms what around the eye
the sclera
the sub-arachnoid space forms what
the choroid space
problems associated with sub-arachnoid space
build up of CSF
papilloedema
compress nerves and blood vessels
why does papilloedema occur?
compresses central retinal vein preventing venous drainage from the eye - swells the optic disk
optic radiation allows what to go where
optic fibres to go along calcarine sulcus to occipital lobe
where does the striate cortex lie?
above and below calcarine sulcus
what’s either side of striate cortex?
Visual association cortex
path of light through eye
light information coming from left hand side goes to right hand retina
what happens to middle section the retinal sides
Blind spot!
path of optic nerves from retina - distinguish path of left from right
nasal part of retina sends information to contralateral side.
Temporal part of retina sending to ipsilateral side.
information from left hand side is interpreted from what side of hemisphere
right hand side
upper visual field goes to which bank of calcarine sulcus
lower bank of calcarine sulcus
lower visual field goes to which bank of calcarine sulcus
upper bank of calcarine sulcus
where does the centre of the visual axis (macula) go?
occipital pole
as you go along calcarine sulcus does vision become more central or peripheral?
central
how do visual field fibres get to lower calcarine sulcus?
inf. horn of lat ventricle
meyer’s loops
scotoma definition
localised patch of blindness
anopia definition
refers to the loss of one of more quadrants of the visual field
hemianopia definition
half of the visual field is lost
quadrantanopia definition
quarter of the visual field is lost
homonymous definition
visual field losses are similar for both sides
heteronymous definition
visual field losses are on different sides
what happens when you cut optic nerve in one eye
blind in one eye
monocular blindness
pituitary gland growth causes what
heteronymous hemianopia
loss of crossing fibres
aka bitemporal hemianopia
optic tract damage
homonymous hemianopia
optic radiation damage
homonymous quadrantanomia (with macula sparing)
both optic radia damaged
homonymous hemianopia (with macula sparing)
tip of occipital pole damage
scotoma
what percentage of fibres goes where?
10% go to the lateral geniculate nucleus of thalamus
what does pupillary light reflex test?
Afferent: optic nerve and tract
Efferent: oculomotor
what muscle constricts the eye? which nerve?
sphincter pupillae (circular) oculomotor short ciliary
what muscles dilates the eye? which nerve?
dilator pupillae (radial) long ciliary
what components are there of pupillary light reflex?
direct
consensual
what is direct component?
light in one eye, same pupil constricts
what is consensual component?
light in one eye, other pupil constricts
how do the pupillary light fibres enter the mid brain?
synapses in pre-tectal area
what sits either side of cerebral aqueduct?
Edniger-Westphal nucleus
What is the Edniger-Westphal nucleus?
Receives ipsilateral and contralateral optic fibres
Parasympathetic oculomotor nucleus
Gives off pre-ganglionic fibre
Where does the pre-ganglionic nerve from the Edniger-Westphal nucleus go to?
Ciliary ganglion (runs with oculomotor nerve)
would your eyes be permanently dilated if one of your optic nerves is damaged?
No
Because oculomotor is intact
would your eyes be permanently dilated if one of your oculomotor nerves is damaged?
Yes
Unopposed sympathetic input
can ask about accommodation reflex
but not until the integrated
