Visual Pathways Flashcards
The intra ocular portion of the optic nerve is how long?
1 mm in length
What is the arterial supply to the intra ocular portion of the optic nerve?
Shorts, posterior ciliary artery, and circle zinn
At the lamina cribosa , ganglion cells are myelinated by…
Oligodendrocytes
What is the maculopapular bundle
Ganglion cells of the macular and via the macular papular bundle which enters the optic disc at centre.
How long is the intraorbital section of the optic nerve?
24mm (longest)
What is the blood supply to the intraorbital section of the optic nerve?
plial vessels and Central collateral artery
What is the blood supply to the intracranial section of the optic nerve?
blood supply: pial plexus, superior hypophyseal and internal carotid branches
What is the path of the intracranial portion of the optic nerves ?
 Passes superiorly medially posteriorly to optic chiasm which is at the floor of the third ventricle
- reaches optic chiasma and the floor of the 3rd ventricle
- above the intracranial portion of optic nerve –> lies the olfactory nerve (C 1)
Superior to optic chiasm is…
Optic chiasm relations
infero-nasal retinal nerve fibres cross chaisma…
> infero-nasal retinal nerve fibres cross
chaisma anteriorly, travel to the contralateral optic nerve before
travelling in the contralateral optic tract
This is known as knee of Von willebrand..
Therefore, lesion on the anterior right aspect of chiasm causes junctional scotoma, ie defect in superior left quadrant
> supero-nasal retinal nerve fibres cross chiasma…
> supero-nasal retinal nerve fibres cross chiasma posteriorly and travel through the the contralateral optic tract
Arterial supply to optic tract?
: branches of anterior choroidal, middle cerebral and posterior communicating arteries
The optic tract rotates by how many degrees
90° while winding round the brain stem
Where is the Lateral gen nucleus located
Pulvinar Thalamus
How many laminated layers does the IGN have
S ix
Optic radiations from Lgn are called
Myers’s loop
Optic radiations from mgn are called
Baum’s loop
Nasal retinal, fibres terminates, in which part of the LGn
1 4 6
Temporal retinal fibres terminate in which area of the LGN
235
LGN blood supply
blood supply anterior choroidal artery and thalamogeniculate
Blood supply to optic radiation
blood supply: anterior radiations supplied by anterior choroidal artery;
posterior Radiations supplied by posterior (mainly) & middle cerebral arteries and lateral striate a.
Optic chasm blood supply
chiasma blood supply: pial plexus supplied by mainly internal carotid arteries, plus superior hypophysial branches, posterior and anterior communicating a. supply
What is meyers loop
> lateral portion of LGN gives rise to Meyer’s loop optic radiations
Meyer’s loop fans laterally within the temporal lobe before swinging posteriorly toward the inferior wall of the calcarine sulcus visual cortex (pg. 93)
Remember PITS
What is Baum loop
Arises from MEDIAL PORTION of LGN which recieves impulses from superior retinal ganglion fibres ie. inferior visual field
medial portion of LGN gives rise to Baum’s loop optic radiations
Baum’s loop fans immediately superiorly and posteriorly within the parietal lobe heading direcIty toward the superior wall of the calcarine sulcus visual cortex
Remember PITS
What are magnocellular cells
Part of the LGN IN LAYERS 1 and 2
Connected to parasol ganglion cells
Responsible for:
Motion detection
Depth perception
Low acuity/resolution
High contrast sensitivity (monochromatic)
Magnocellular cells receive input from
Parasol ganglion cells
Parasol ganglia cell function
What are parvocellular cells
Part IGN in layer 3-6
parvocellular cells receive input from..
Midget ganglion cells
Midget ganglion cells are responsible for
Kiniocellular cells in Lgn receive input from
Bistratified ganglion cells which are connected to rods and cones
Brodmann’s area 17 is the
Primary visual cortex
Most optic radiations terminate in which area of the primary visual cortex
Layer 4 (some in 6)
Play five of the primary visual cortex is connected to…
Superior collículos to inform eye movement
The right visual field is controlled by which area in the primary cortex
The left ( all inverted, ie superior field, controlled by inferior aspects of cortex)
The secondary visual areas are known as…
Brodmann area 18 & 19, aka extra striate cortex
What are the blood vessels to the visual parts of the brain?
Blood supply to brain tissue concerned with vision
> middle cerebral artery supplies the frontal eye field <
> posterior (mainly) & middle cerebral arteries supply the visual cortex <
> calcarine artery (branch of posterior cerebral) supplies the visual cortex <
pathology in the FEF leads…
to a conjugate gaze deviation toward the side of the damage (ipsilateral gaze defect)
PARAMEDIAN PONTINE RETICULAR FORMATION (PPFR) lesion causes…
cause loss of horizontal saccades toward the side of the lesion and/or horizontal gaze deviation which are evident clinically
What is the path of the intracanalicular aspect of ophthalmic nerve
- optic canal lies within the lesser wing of the sphenoid bone
- meninges continue through the optic canal
- dura fuses with periorbita which fixes nerve
- ophthalmic artery passes inferolaterally to optic nerve in the optic canal
What is the blood supply to the intracanalicular aspect of optic nerve.
Plial plexus and branches of ophthalmic artery
