Anatomy Of Visual Systems - Week 6 ***printed***

Front 1

Visual Pathway Overview

Back 1

(first three cells are in retina - extention of CNS)
Synapse 1: Receptor cell
Synapse 2: Bipolar cell
Synapse 3: Tanglion cell
-axons=optic nerve->chiasm->optic tract
Synapse 4: lateral geniculate nucleus neuron
-axons->optic radiation
Synapse 5: Visual cortex neuron (striate cortex)

Front 2

Visual Pathway Structures

Back 2

-retina
-optic nerve
-optic chiasm
-optic tract
-LGN
-optic radiations
-straite cortex

Front 3

Optic Nerve

Back 3

Dimensions: length: 4-6cm
-intraocular: (axons and ganglion) not very long
-intraorbital: (posterior aspect of eye to optic canal) significantly longer portion
-intracanal: (segment just through optic canal)
-Intracranial: (from posterior aspect of optic canal to chiasm)
***get actual lengths from book***

Front 4

Optic Nerve: Diameter:

Back 4

Intraocular Diameter: 1.5mm
-1-2 million axons
-bundled into fasicles (1,000 fibers by sheaths of astrocytes per fasicle)

Postlaminar Diameter:
-3mm (approximately doubles)
-fasicles acquire additional CT sheath
-nerve fibers become myelinated (nonmyelinated in retina)

Front 5

Lamina Cribrosa

Back 5

Network of scleral fibers through which the optic nerve fibers exit the eye.

Front 6

Optic Nerve Relations with Meningeal Sheaths

Back 6

-Dura, pia, and arachnoid are continuous with those covering brain
(figure 13-3)

Front 7

Different Levels of Glia Cells

Back 7

figure 13-2
1) Intermediary Tissue of Kuhnt (#5)
-glia at level of retina

2) Border tissue of Jacoby (#4)
-glia at level of choroid (more posterior)

3)Marginal tissue of Elschnig (#3)
-connective tissue continuous with sclera

**glial tissue
**supported by tight junctions (limits what can pass through area)

Front 8

Optic Nerve Relations:

Back 8

-inferior to olfactory tract and anterior cerebral artery

-lateral to sphenoidal sinus (body of sphenoid)

-sheath is attached to EOM sheaths
->medial rectus
->superior rectus
**in optic neuritis, pain often accompanies eye movement because dura is pain sensitive (meningeal sheaths)

Front 9

Optic Nerve Blood Supply:

Back 9

*prelaminar (within optic disc) and laminar (area of lamina cribrosa):
-unfenestrated peripapillary (area around optic nerve head) choroidal network

*postlaminar (optic nerve past lamine cribrosa):
-ophthalmic
-central retinal artery
-pial vessel

*Intracranial:
-ophthalmic
-anterior cerebral
-anterior communicating
-internal carotid

Front 10

Optic Chiasm: Location, Relations and Blood Supply

Back 10

(figure 13-4)
Location: surrounded by Circle of Willis (anterior, lateral, posterior)
Relations:
-posterior to anterior cerebral and communicating arteries
-medial to internal carotid
-inferior to third ventricle
-superior to pituitary gland
Blood Supply:
-superior network: anterior cerebral and communicating
-inferior network: posterior cerebral and communicating internal carotid

Front 11

Optic Tract: Description and Location

Back 11

-flattened cylindrical band from chiasm to LGN

-some fibers, about 10%, go to pretectal area (pupillary light response) and superior colliculus (reflexive eye movement)

Front 12

Optic Tract: Relations and Blood Supply

Back 12

Relations:
-lateral to cerebral peduncle
-parallel to posterior cerebral artery, anterior carotal
-posterior communicating crosses optic tract inferiorly
-inferior to globus pallidus (portion of basal ganglia)

Blood Supply:
-anterior choroidal
-middle cerebral

Front 13

Lateral Geniculate Nucleus (body) = External Geniculate Nucleus
--> appearance and location

Back 13

(figure 13-7)
-assymmetrical and cone-shaped
-dorsal lateral thalamus
-magnocellular layers (inferior layers)
-parvocellular layers (superior four layers; medium size cells)
-konicellular layers (sandwiched between each layer; very small cells)

Front 14

Lateral Geniculate Nucleus (body) = External Geniculate Nucleus
--> function

Back 14

Function:
-some visual processing
-ensures that most important information is sent to visual cortex
-->has efferent to visual cortex and some subcortical areas
-->has afferent (reciprocals) from visual cortex

Front 15

Lateral Geniculate Nucleus (body) = External Geniculate Nucleus
--> relations, blood supply

Back 15

Relations:
-medial to internal capsule
-lateral to medial geniculate nucleus (associated with hearing)
-medial to inferior horn of lateral ventricle

Blood Supply:
-anterior choroidal
-posterior choroidal