The visual pathway

Question 1

What is the start to end of the visual pathway

Answer 1

ganglion cell axons

Optic nerve

Optic Chiasm

OPtic tract

Lateral geniculate body (LGB)

Optic radiation

Visual cortex

Question 2

What will happen if a lesion happens along the visual pathway

Answer 2

Visual field loss will occur (note that nasal half of retina sees the temporal part of the obj.)

Question 3

What is the field of vision

Answer 3

100 temporal

60 nasal

120 central (binocular vision)

60 superior

75 inferiorly

Question 4

What does the optic nerve contain

Answer 4

Millions of axons derived from the retinal ganglion

Question 5

What is the optic nerve subdivided into

Answer 5

Intra-ocular (eye)
- retinal surface of optic disc to sclera

Intra orbital (orbit)
- Globe to optic canal

Intracanlicular (canal)
- Passes thr optic canal

Intracranial (head)
- leaves canal to reach optic chiasma

Question 6

What is the blood supply of the intra ocular portion of the optic nerve

Answer 6

Branches of circle of Zinn-Haller and short posterior ciliary arteries

Question 7

What is the blood supply of intra orbital portion of optic nerve

Answer 7

Pial plexus of vessels, central collateral arteries (central retinal artery)

Question 8

What is blood supply of the intracanalicular portion of the optic nerve

Answer 8

Branches from pial plexus

Question 9

What makes the circle of willis

Answer 9

Anterior communicating artery

Anterior cerebral arttery

Internal carotid artery

Posterior commmunicating artery

posterior cerebral artery

Question 10

Which nerve fibres cross and do not cross at the optic chiasma

Answer 10

Fibres from nasal half of retina decussate a and cross to opp. optic tract
- partial crossing essential for binocular vision

Fibres from temporal half of the retina do not cross but pass back into the optic tract of the same side

Question 11

What is the blood supply of the optic chiasma

Answer 11

Branches from the internal carotid artery

Question 12

Which fibres are the optic tract derived from

Answer 12

Form nasal nerve fibres from opp. side and temporal nerve fibres from same side of the retina

Question 13

Where do the fibres reach after the optic tract

Answer 13

90% of nerve fibres reach lateral geniculate body

Some distrbuted to
- superior colliculus (eye reflex)
- pretectal nuclues (pupillary reflex)

Question 14

Describe the LGB

Answer 14

Axons of retinal ganglion cells synapse here in a specific layering pattern

Recives nasal nerve fibre from opp. side and temporal nerve fibres from same side of the retina

Question 15

What does LGB play a part in

Answer 15

Modify pattern of the strength of retinal signals and plays a part in stereopsis and colour vision

Question 16

Describe the optic radiation

Answer 16

Arise from LGB to relay messagesto occipital lobe at striate region

Question 17

What are the two parts of visual cortex

Answer 17

Primary visual cortex (straite cortex)

Secondary visual cortex

Question 18

Type of cells in the primary visual cortex

Answer 18

Simple, complex and hypercomplex

Question 19

How does the receptive field differ in the cortex vs the retina

Answer 19

Receptive fields as mapped out in the cortex differs from those in the retina without the concentric circularly symmetrical pattern

Question 20

How is the perception of edges perceived

Answer 20

Combination by simple and complex cells

Combined action of simple and complex cells provide the neuronal basis of perceiving edges, borders, boundaries and contrasts

Question 21

What is the function of the primary visual cortex

Answer 21

Detection of lines and borders, orientation of lines lines and borders, line position and length of lines/ detects lines and borders

Question 22

What is the function of the secondary visual cortex

Answer 22

Interpret signals from primary visual cortex and allows one to recall memory of previous sensory experience/ responsible for visual memory

Extra:
- recognition of objects but not recognition of written or printed symbols of language
- recall of visual memory relating to obj. but not to language symbols