Visual Pathway

Front 1

What is the route of the Visual pathway?

Back 1

Optic nerve

Optic chiasma

Optic tract

Lateral geniculate nucleus

Optic radiations

Visual cortex

Front 2

Label the following

Back 2

Front 3

Label the optic nerve cross section

Back 3

Front 4

What are the 4 parts to the optic nerve?

Back 4

Intraocular (1mm)

Intraorbital (30mm)

Intracanicular (6-9mm)

Intracranial (10mm)

Front 5

What is the intraocular part of the optic nerve?

Back 5

• Passes through sclera, Choroid and appears in eye as optic disc.

• It consists of 4 portions

Front 6

What are the 4 portions of the intraocular part of the optic nerve?

Back 6

From anterior to posterior:

a) surface nerve fibre layer.

b) prelaminar region.

c) lamina cribrosa.

d) retrolaminar region.

Front 7

What is the Intraorbital part?

Back 7

• Extends from back of eyeball to optic foramina.

• Surrounded 3 layers of meninges & subarachnoid space.

•Near optic foramina, optic nerve surrounded by annulus of Zinn & the origin of four recti muscles.

• Some fibres of superior & medial rectus are adherent to its sheath so painful ocular movement in retrobulbar neuritis.

Front 8

Describe the Internal structure of the Intraorbital portion.

Back 8

•Myelination

•20-30 mm Long

•Axons: myelin and glial cell (metabolic support)

Front 9

What and Where is the intracanalicular portion?

Back 9

• Medial wall of canal forms lateral wall of sphenoid

• Within canal: meninges, ophthalmic artery and sympathetic plexus.

• 10 mm length

• Related to ophthalmic artery.

Front 10

What is the intracranial part?

Back 10

•Leaves the cranial end of the optic canal (medially, backwards, upwards).

•4-15 mm (depending on the position of chiasm).

•Lies above cavernous sinus & converges with its fellow to form chiasm.

•Sheathed in pia mater.

Front 11

What is the optic chiasma?

Back 11

Area where nerve fibres arising from nasal half of two retina decussate at the chiasm.

Front 12

How big is the optic chiasm?

Back 12

•12mm wide

•8mm Anterio-posteriory

•Flat structure

•4 mm thick

Front 13

What is the blood supply around the chiasma?

Back 13

Front 14

What are the optic tracts?

Back 14

• Bundles of nerve fibres running outwards and backwards from postero-lateral aspect of the optic chiasm.

Front 15

What do the optic tracts consist of?

Back 15

• Fibres from temporal half of retina of same eye & nasal half of opposite eye.

• Posteriorly each ends in Lateral Geniculate Nucleus

Front 16

What is the lateral geniculate nucleus?

Back 16

Oval structures situated at termination of the optic tracts.

Front 17

What does the lateral geniculate nucleus consist of?

Back 17

Each consist of 6 layers of neurons (grey matter) alternating with white matter (optic fibres)

Front 18

What are the 2 main layers of the lateral geniculate nucleus?

Back 18

• Parvocellular layers

•Magnocellular layers

Front 19

What are the Parvocellular layers ?

Back 19

(Form and Colour):

• small cells, color sensitive

• high spatial resolution (small RF)

•low temporal resolution (does not see fast flickers of light)

•Receive inputs from P type Retinal cells.

Front 20

What are the Magnocellular layers?

Back 20

(motion):

• large cells, color blind

• low spatial resolution (large RF)

•high temporal resolution (good for processing motion stimuli)

• They receive inputs from M type retinal cells.

Front 21

What is the function of the lateral geniculate nucleus?

Back 21

• Relay station to relay visual information from optic tract to visual cortex.

• To gate transmission of signal to visual cortex.

Front 22

What layers of the lateral geniculate nucleus, do the contralateral fibres go to?

Back 22

Crossed fibers -1,4,6

Front 23

What layers of the lateral geniculate nucleus, do the ipsilateral fibres go to?

Back 23

Uncrossed fibers - 2,3,5

Front 24

What is the posterior aspect of the lateral geniculate nucleus represent?

Back 24

Posterior aspect represents central 15-20 degrees of visual field

Front 25

What is the anterior aspect of the lateral geniculate nucleus represent?

Back 25

Anterior aspect has 4 layers, layers 4 and 6 merge, and 3 and 5, represents the peripheral field

Front 26

What are the K layers?

Back 26

Between each of the M and P layers. K cells are functionally and neurochemically distinct from M and P cells and provide a third channel to the visual cortex.

Front 27

What are the optic radiations?

Back 27

• Extends from the LGN to the visual cortex.

• Fibres ascend before sweeping laterally as well as posteriorly

Front 28

Where do the medial and lateral fibres from the LGN through the optic tracts go?

Back 28

• Fibres in medial aspect travel straight to visual cortex.

(Peritial lobe)

superior retinal fibres

• Fibres in lateral aspect sweep forward then loop around – Meyer’s loop.

(Temporal lobe)

inferior retinal fibres

Front 29

What are the temporal lobe/radiations

Back 29

• Consist of inferior retinal fibres (superior visual field).

• Macula splitting

•Blood supply -Posterior cerebral artery but also supply visual cortex

Front 30

What is the Peritial lobe/ radiations?

Back 30

• Consists of superior retinal fibres pass proceed directly toward the visual cortex

•Blood supply middle cerebral artery

•Fibres deep within the parietal lobe are more closely grouped.

Front 31

What the 3 major parts of the Brain?

Back 31

• Cerebrum - 4 lobes

• Cerebellum

• Brain stem

Front 32

What is the Cerebrum?

Back 32

•Largest part of the brain

•Right and left hemispheres

Front 33

What is the function of the cerebrum?

Back 33

Performs higher functions

• touch

• vision

• hearing

• speech

• reasoning

• emotion

• learning

• fine control of movement

Front 34

Where is the cerebellum?

Back 34

Located under the cerebrum

Front 35

What is the function of the cerebellum?

Back 35

• coordinate muscle movements

• maintain posture

• maintain balance

Front 36

What does the Brain stem consist of?

Back 36

Includes the midbrain, pons, and medulla

Front 37

What is the function of the Brain stem?

Back 37

•Relay center connecting the cerebrum and cerebellum to the spinal cord.

•Performs many automatic functions such as breathing, heart rate, body temperature, wake and sleep cycles, digestion, sneezing, coughing, vomiting, and swallowing.

Front 38

What originates from the brainstem?

Back 38

10 of the 12 cranial nerves

Front 39

What is the visual cortex?

Back 39

•Outer 4-6 mm cerebrum

•Grey matter – large number ofnerve cells

•Underlying white matter

•Embryological development - grey matter folds

•Deep folds fissures

•Shallower folds sulci

•Cortex – two hemispheres

•Visual cortex area that receives visual input

Front 40

Where is the visual cortex located?

Back 40

•On medial aspect of occipital lobe

• Divided into areas:

-Striate area 17

-Striate area 18 and 19

Front 41

What is the primary visual cortex?

Back 41

Also know as the striate cortex where the perception of the visual stimuli become what we see.

Front 42

What does the primary visual cortex consist of?

Back 42

•Brodmann’s area 17

• V1

•Visual cortex

• Striate cortex

Front 43

What are simple cortical cells?

Back 43

•Respond best to bars or edges of light in a particular location in the receptive field and in a particular orientation (e.g., 45 degrees)

• All simple cells are monocular

• They also have on and off areas