Neuro: Visual Pathways

Question 1

The retina is divided into two regions and this structure separatees the nasal hemifield from the temporal hemifield.

Answer 1

Macula Lutea

Question 2

In the retina, what is the function of ON center cells vs. OFF center cells?

Answer 2

ON center cells inhibit Bipolar cell depolarization in the dark. They are used to see light.

OFF center cells stimulate Bipolar cell depolarization in the dark and are used to see in the dark.

Question 3

Axons come from the retina and pass thru the optic nerve, chiasm, and tract then pass to the:

Suprachiasmatic Nucleus of the Hypothalamus for what purpose?

Answer 3

Regulate circadian rhythm/wake sleep cycle

Question 4

Axons come from the retina and pass thru the optic nerve, chiasm, and tract then pass to the:

Lateral Geniculate Nucleus of the Thalamus for what purpose?

Answer 4

To be transmitted up to the visual cortex for interpretation.

Question 5

Axons come from the retina and pass thru the optic nerve, chiasm, and tract then pass to the:

Superior Colliculus for what purpose?

Answer 5

Visual tracking of moving objects (or stationary objects while viewer is moving)

The axons in this pathway follow the axons that terminate in the lateral geniculate nucleus but these axons travel thru the Brachium of the Superior Colliculus and travel into the superior colliculus.

Question 6

Axons come from the retina and pass thru the optic nerve, chiasm, and tract then pass to the:

Pretectal Area for what purpose?

Answer 6

Pupillary light reflex

Question 7

What type of deficit would occur from an aneursym compressing one optic nerve?

Answer 7

Ipsilateral vision loss in the eye and diminished or absent pupillary light reflex in the ipsilateral eye.

Question 8

What type of visual deficit would result from a pituitary tumor compressing the optic chiasm?

Answer 8

Pinches all the crossing fibers. Results in tunnel vision.

Question 9

Every point in our visual field that is picked up with both eyes is sent back to the primary visual cortex and the information of each point is analyzed thru six layers of cells called a “column”. Which layers in this column deal with the nasal hemifield and which deal with the temporal hemifield?

Answer 9

Nasal: 1, 4, and 6
Temporal: 2, 3, and 5

Question 10

Axons carrying visual info travel to the lateral geniculate nucleus where they synapse and then travel to the primary visual cortex on 2 different pathways. Name then and what type of information they carry.

Answer 10

1. Magnocellular: rods, info on brightness

2. Parvocellular: cones, color and acuity

Question 11

What region of the brain makes up the Primary Visual Cortex.

Answer 11

Internal portions of the cuneate (superior bank) and lingual (inferior bank) gyri that border the calcarine sulcus.

Question 12

Describe the pathway that a light signal travels in the pupillary light reflex.

Answer 12

1. CN II ——> Pretectal Area
2. Pretectal Area ——-> Edinger Westphal Nucleus
3. EWN ———-> CN III
4. CN III ——–> iris

Question 13

Describe the pathway that a neuron signals travel for visual motion tracking.

Answer 13

1. CN II ——-> superior colliculus
2. SC ——> pulvinar + lateral posterior nucleus of thalamus
3. Pul + LPN ——-> parietal cortex
4. Par Cx ——-> frontal eye field

Question 14

Name the two OPTIC radiations that arise from the Lateral Geniculate Nucleus and what type of information they carry.

Answer 14

1. Baum’s Loop (dorsomedial LGN): lower visual field
2. Meyer’s Loop (ventrolateral LGN): upper visual field

(baums is actually located superior to meyers even though it carriers lower visual field)

Question 15

What occurs from lesions to Baum’s and Meyer’s loops>

Answer 15

Baum’s: Pie in the floor
(Baums axons are located somewhat in the parietal lobe)
Meyer’s: Pie in the sky
(meyers axons are located somewhat in the temporal lobe)

Question 16

Strokes and vascular occlusions can result in vision loss. Why is the macula usually spared in these instances?

Answer 16

The macula has two major blood supplies and is often spared.

receives blood supply from posterior cerebral and middle cerebral arteries

Question 17

Which of the 6 layers of the columns in the primary visual cortex receives most of the visual information from the Lateral Geniculate Nucleus?

Answer 17

Layer 4

Question 18

The primary visual cortex is also called striate cortex because it has an extra band of white matter called what?

Answer 18

Stria of Gennari