Visual Pathway ( McMahon ) Flashcards
What are the 4 cells involved in the pathway
Photoreceptor cells
Bipolar Neurons
Ganglion Cells
Neurons of Lateral Geniculate Body in Thalamus
What is the photoreceptor cells made up of and what do they do
Rods and Cones
Rods for night vision
Cones for colour vision
What do the bipolar neurons do
Connects rods and cones to ganglion cells
What makes up the ganglion cells ( axons pass to where )
axons pass to thalamus
Where does the axons of LGN of thalamus pass to
Visual Cortex
What does the pigment epithelial layer contain when what is the function of the pigment cells
Contains melanin and absorbs light that passes through retina
How many rods and cones do we have
Rods : 110 - 125 mill
Cones : 6 - 7 mill
What axons form the optic nerve
Axons of ganglion cells
Bipolar cells have interneurons, what are they
Amacrine and Horizontal cells
Where do you get acute vision
Fovea
What do you call the area surrounding the fovea
Macula Lutea
The line connecting fovea and viewed objects is called as
Visual Axis
What kind of cells do you find in the floor of fovea
Cones
Inner retinal layer allows light rays to reach without having to cross other layers
What is the optic disc
An area at which unmyelinated optic nerve fibers exit retina but fibers will become myelinated as emerge
What is the optic nerve myelinated by
Oligodendrocytes hence cannot be regenerated once damaged
Image of object in right field of vision will be projected onto
Nasal half of right retina ( R )
Temporal half of left retina ( L )
Right field vision will be projected on L / R visual cortex?
Left
Which fibers will cross midline? Fibers from nasal half or medial half
Nasal half will cross over
The fibers terminate by synapsing with ( )
LGN of thalamus
LGN will give rise to optic radiation and the most anterior fibers will form ( )
Loop of Meyer
In the Lateral Geniculate Body, where will neurons project complete left field of vision onto visual cortex of the right hemisphere? ( what is the area )
Area 17
A pituitary tumour may damage what ?
The optic chiasm
How is the optic chiasm related to the internal carotid?
Internal carotid is lateral to chasm so aneurysm will damage lateral part of chiasm
Some fibres of the optic tract will pass from lateral geniculate to ( 2 ) and what are they concerned w
Pretectal nucleus
Sup colliculus of midbrain
Concerned w the light reflexes
What is direct light reflex
When the pupil that eye is shone light constricts
What is consensual light reflex
Constriction of opposite pupil
Impulses will travel through ( 4 )
Optic Nerve
Optic Chiasm
Optic tract
Synapses on nerves in pretectal nucleus
Describe the light reflex ( only up till ciliary ganglion )
Impulse pass to CNIII of affected eye
Synapses on pretectal nucleus of affected eye
Impulse travels to the Edinger - Westphal of both eyes
Impulses pass to ciliary ganglion in orbit
Where does the impulse pass to from the ciliary ganglion in orbit ( 2 )
To short ciliary nerves at eyeball
Constrictor pupillary muscle of iris
Causes constriction of both pupils
When does the accommodation reflex occur
When eye is directed from distant to near object
What muscles of the eye is involved in the accommodation reflex, what happens to it and what does it cause
The medial rectus muscle of both eyes would contract and this causes convergence of eyes
Why does the lens thicken and how does it thicken
To increase refractive power
The contraction of ciliary muscle helps thicken it
