Visual System

Question 1

Describe the components of the retina. Where is the first AP?

Answer 1

Bipolar cells, photoreceptors (rods and cones), and ganglion cells. NO APs in photoreceptors – first AP in ganglion cells. Photoreceptors are neuromodulators.

Question 2

Define Rods and Cones and their properties.

Answer 2

Photoreceptors (which are neuromodulators). Rods=highly sensitive, low acuity. Cones=low sensitivity, high acuity.

Question 3

Which photoreceptor is predominant at the fovea?

Answer 3

Cones. Highest acuity. Fovea contributes most to lateral geniculate.

Question 4

What is the optic nerve made up of?

Answer 4

Ganglion cell axons.

Question 5

SLO

Answer 5

Superior calliculous, lateral geniculate body, optic stuff (area 17).

Question 6

What are the two types of ganglion cells?

Answer 6

1. M-type: Rods, respond to movement.

2. P-type: Cones, respond to color and fine detail.

Question 7

What is the visual cortex?

Answer 7

Area 17

Question 8

What is the pretectal area?

Answer 8

Pupillary reflexes (Edinger-Westphal)

Question 9

What does the superior colliculous control?

Answer 9

Head and eye movements (orienting reflex, MLF).

Question 10

Describe orientation of visual field and path of fibers from lateral geniculate to area 17.

Answer 10

Upper fibers = lower visual field, via parietal lobe.

Lower fibers = upper visual field, via temporal lobe (Meyer’s loop)

Question 11

Describe visual path from retina

Answer 11

Light -> retina -> optic nerve -> optic chiasm -> optic tract -> lateral geniculate -> area 17.

Question 12

Describe light reflex

Answer 12

Causes pupillary constriction (both direct and consensual). Light -> optic nerve -> superior colliculus -> pretectal area, Edinger-Westphal -> CN III (occulomotor n.) -> ciliary ganglion -> constriction of pupil. Light reflex strictly via brainstem.

Question 13

Describe blink reflex

Answer 13

Causes corneal blink both direct and consensual via CN VII.

Question 14

Describe accommodation reflex

Answer 14

Requires visual cortex.

Question 15

What is the injury that causes Blind Right Eye?

Answer 15

Injured right optic nerve

Question 16

What injury causes Bilateral Hemianopia?

Answer 16

Injured optic chiasm. Loss of peripheral field.

Question 17

What injury causes Left Homonymous Hemianopia?

Answer 17

Injured right lateral geniculate or injured right optic tract. Loss of left visual field in both eyes.

Question 18

What injury causes Left Homonymous Upper Quadrantanopia?

Answer 18

Injured Meyer’s loop (inferior fibers). Loss of upper visual field.

Question 19

What injury causes Left Homonymous Lower Quadrantanopia?

Answer 19

Injury to upper fibers (parietal) from lateral geniculate to area 17. Loss of lower visual field.

Question 20

What injury causes Left Homonymous Hemianopia with Macular Sparing?

Answer 20

Injury to all fibers by right side area 17. Loss of left visual field except at center (fovea).

Question 21

Describe cortical processing and the function of cortical layers

Answer 21

Cortical processing: more complex as you move up cortical layers. Layer four (input) is larger in visual cortex than in other layers. Layer five = output.

Question 22

Describe the three types of hypercolumns

Answer 22

1. Orientation
2. Blobs - color specificity
3. Ocular dominance: left vs right

Question 23

Distinguish between parietal and temporal lobe detection of vision

Answer 23

Parietal lobe = where object is

Temporal lobe = what object is