Week 4 Vision Objective 4

Question 1

Amacrine cells (the flashcard with tons of stuff on it)

Answer 1

30 kinds

One kind involved in direct conduction for rod pathway

One type responds strongly at the offset of visual signal but fades quickly

One type responds strongly at the onset of visual signal but fades quickly

Some respond when light is turned on/off

One responds to movement of a spot across retina in a specific direction

MOST ARE INTERNEURONS that help analyze visual signals before they leave retina

Question 2

Ganglion cells

Answer 2

average 60 rods and 2 cones converge on each ganglion cell, and the optic nerve fiber from ganglion cell

approaching fovea, fewer rods/cones converge on each optic fiber, rods/cones become slender

this increases visual acuity in central retina

Question 3

in central fovea, there are only what “shaped” cones?

Answer 3

slender and no rods

Question 4

Weak light stimulates what part of the retina?

Answer 4

all of it, but the peripheral region the most

as many as 200 rods converge on a single optic fiber in these regions

Question 5

Types of Ganglion Cells (just name them)

Answer 5

W X Y

Question 6

W Ganglion

Answer 6

Make up around 40% of ganglia

8m/sec

small

receives signals mostly from bipolar and amacrine cells

broadly distributed dendria in peripheral fields

Question 7

X Ganglion cells

Answer 7

make up about 55% of ganglia

14 m/sec

medium diameter

small fields receiving discrete retinal signals

receives input from at least one cone cell, so probably responsible for color vision

Question 8

Y Ganglion cells

Answer 8

makes up 5% of all ganglion cells

large diameter

50m/sec or faster

respond to rapid changes in visual image

apprise CNS almost instantaneously when new visual signals occur anywhere in field without

lacks great accuracy or respect to location of field