Visual System

Question 1

M ganglion cells

Answer 1

• AKA y
• largest
• extensive dendritic arbors
• large receptive fields
• periphery
• rods input

Question 2

P ganglion cells

Answer 2

AKA X

• small dendritic arbors
• small receptive fields
• in central retina
• input from cones

Question 3

W ganglion cells

Answer 3

• non uniform

- various receptive field size and physiologic response

Question 4

Where does CN II leave brainstem, reside in skull and where does it exit?

Answer 4

exits orbit, through optic canal into middle cranial fossa

-does not join brainstem

Question 5

optic chiasm

Answer 5

where optic nerves converge and then split again to form optic tracts

Question 6

visual pathway

Answer 6

optic nerve
optic chiasm (1/2 fibers cross (nasal))
optic tract (to lateral geniculate nucleus (LGN) also to superior colliculus and pretectum)
optic radiation (from LGN to V1/visual cortex)

Question 7

LGN layers (how many and name of layers only)

Answer 7

6 layers
magnocellular layers (1,2) and parvocellular layers (3-6)
1M and 2P per eye

Question 8

Magnocellular layers

Answer 8

• layers 1, 2
• large cells
• movement and contrast
• from M cells

Question 9

Parvocellular layers

Answer 9

• layers 3-6
• small cells
• form and colour
• from p cells

Question 10

Optic radiations

from/to

Answer 10

From LGN to primary visual cortex

• upper visual field to inferior optic radiations, terminate in inferior V1 (below calcarine fissure)
• lower visual field to superior optic radiations, terminate in superior V1 (above calcarine fissure)

Question 11

Projection of peripheral vs central vision in V1

Answer 11

peripheral vision is anterior

central vision is posterior

Question 12

Simple vs Complex cells of V1/Area 17

Answer 12

simple respond to orientation of a line

complex may be direction sensitive or respond best to a corner, cross or X

Question 13

Cortex layers and LGN synapsing

Answer 13

LGN synapse on layer IV
layer IV mostly monocular
layer II/III, V, and VI binocular (but most have preference for one eye’s input)

Question 14

orientation column

Answer 14

cell column in primary visual cortex that prefers same line or orientation (ie all cells in column will fire for vertical but not horizontal line)

Question 15

ocular dominance column

Answer 15

cell column in primary visual cortex that responds to L or R eye (or strong preference)

Question 16

colour sensitive region

Answer 16

cell clusters in primary visual cortex that respond to colour

Question 17

hypercolumn

Answer 17

set of orientation and ocular dominance columns in primary visual cortex that receive input from given point in visual field (ice cube model)

Question 18

extrastriate visual areas

Answer 18

primary visual cortex projects here

requires complex stimuli

Question 19

Dorsal (m) stream

Answer 19

where
-to posterior parietal association cortex
-perception of motion
V5

Question 20

ventral (p) stream

Answer 20

what
-to inferior temporal association cortex
-size/shape/colour/orientation
V4

Question 21

Optic tract to Superior colliculus

Answer 21

• role in visual orienting reflexes via tectospinal tract

- in midbrain

Question 22

optic tract to pretectum

Answer 22

• in midbrain

- from pretectum, BILATERAL projections to Edinger Westphal nucleus

Question 23

pupillary light reflex

Answer 23

• info from pretectal nucleus to Edinger westphal nucleus (bilaterally)
• PSN fibers from EWN travel with CN III to ipsilateral ciliary ganglion to sphincter pupillae

This is why light in one eye makes both pupils change

Question 24

direct vs consensual light reflex

Answer 24

direct: illuminated eye response

consensual; non illuminated eye response