Flashcards in Von Bartheld- Vision II Deck (55)
What is considered the "gateway to the cortex"?
lateral geniculate nucleus
What are the four CNS targets of retinal ganglion cells?
lateral geniculate nucleus (LGN)
Why would retinal ganglion cells want to target the pretectum?
for the pupillary light reflex
Why would retinal ganglion cells want to target the hypothalamus?
for circadian rhythm
Why would retinal ganglion cells want to target the superior colliculus?
visual reflexes; eye and head movements
What is the major target of ganglion cell axons in the optic tract in the diencephalon?
the dorsal lateral geniculate nucleus of the thalamus
How do neurons of the dorsal lateral geniculate nucleus of the thalamus send their axons to the cerebral cortex?
via a part of the internal capsule called the optic radiation and then terminates in the primary visual cortex (V1) or striate cortex of the calcarine fissure in the occipital lobe
What happens if you damage your retinogeniculostriate pathway (primary visual pathway)?
serious visual impairment
What does the edinger wesphal nucleus carry?
Explain how you get constriction of pupils?
light->bilateral projections from retina go to pretectum (b/w thalamus and midbrain). Pretectal neurons project to edinger westphal nucleus in the midbrain->sends its parasympathetic preganglionics to ocuolomotor nerve (CN 3) to terminate on neurons in ciliary ganglion. Neurons of ciliary ganglion innervate the constrictor muscles of the iris which decreases diameter of pupil when activated..... SO when you shine a light in someones eye it constricts!
Why do you get bilateral constriction of pupils when you shine a light in someones eyes?
because your pretectal neurons send axons to BOTH Edinger westphal nuclei!
Where is the suprachiasmatic nucleus located and what does it do?
Base of diencephalon, circcadian rhythm
Where is the superior colliculus and what does it do?
midbrain, coordinates head and eye movements
Explain sympathetic control of pupil dilation
retina tells pretectum which tells the superior cervical ganglion to send postganglionc sympathetics up the internal carotid and into the short and long ciliary nerves to innervates dilator pupillae muscle
projections to the lateral geniculate nucleus arise from ganglion cells who specialize mediating what?
richness of visual perception (high acuity, color, motion)
Projections to the hypothalamus and prectum arise from ganglion cells that are only suited for detecting (blank)
Following damage of the visual cortex or lesions of the pathways to the visual cortex what will remain? what has been said to be associated with this?
the subcortical pathway
What is blindsight?
it is when you cannot see because your visual cortex is damaged or you have a broken visual pathway BUT when given a visual stimuli, patients can guess what it is!!!
What is the binocular visual field?
FP until before peripheral vision
Mixing of the pathways (right and left eyes) does not happen until the level of the (blank). Are the fibers mixed at the LGN?
Explain to me what binocular disparities are
each eye sees an object at a slightly different angle and are constantly compensating to make their focus equal. The disparities are interpreted as differences in depth and are fused.
What is this:
the perception of depth produced by the reception in the brain of visual stimuli from both eyes in combination; binocular vision.
Explain the course of the optic radiation to the visual (striate) cortex
axons carrying info about superior portion of visual field sweep around the lateal horn of ventricle in the temporal lobe (meyers loop) before reaching the occipital lobe. Those carring inferior portion of the visual field travel in the parietal lobe
I.e inferior retinal quadrants give you superior visual field.
superior retinal quadrants give you inferior visual field
Tell me about the fovea and retinotopy
the fovea comprises one of the smallest areas of retinal surface area but makes up half the visual cortex.
V1 is the primary visual cortex. What are the secondary (extrastriate cortices) cortices?
V2, V3, V4, VP, MT
Is there only one retinotopic map?
no there are many
Crossing of nasal retinal ganglion cell axons in the chiasm do what?
Projects the right visual field to the left side of the brain and the left visual field to the right side of the brain
Several circular retinal ganglion cell receptive fields combine to form (blank) on individual neurons in cortex.
How do we get a singular complete image to the cortex?
rods and cons create an image and send it to the retina which will send affarent fibers to synapse in the LGN which will go to the cortex which will create a simple field that unifies all the info