Lecture 8: Vision II

Question 1

What are the layers of the retina (in order)?

Answer 1

Photoreceptors, horizontal cells, bipolar cells, amacrine cells, ganglion cells

Question 2

Photoreceptors

Answer 2

Rods, cones; transmit signals to outer plexiform layer, synapse with bipolar and horizontal cells

Question 3

Horizontal cells

Answer 3

Transmit signals from rods/cones to bipolar cells; transmits signals to outer plexiform layer; output always inhibitory

Question 4

Bipolar cells

Answer 4

Transmit signals from rods/cones/horizontal cells; transmit signals to inner plexiform layer; synapse with amacrine, ganglion cells

Question 5

Amacrine cells

Answer 5

Interneurons that help analyze visual signals before the leave the retina

Question 6

Ganglion cells

Answer 6

Transmit signals from retina to brain; axons make up optic nerves

Question 7

What cells make up the optic nerves?

A. Horizontal cells
B. Ganglion cells
C. Bipolar cells
D. Amacrine cells

Answer 7

B. Ganglion cells

Question 8

What is the neuronal pathway for cones?

Answer 8

3 neurons: Cones, Bipolar cells, Ganglion cells

Question 9

What is the neuronal pathway for rods?

Answer 9

4 neurons: Rods, Bipolar cells, Amacrine cells, Ganglion cells

Question 10

What neurotransmitter is involved with signaling between rods/cones and bipolar cells?

A. GABA
B. Glycine
C. Glutamate
D. Dopamine

Answer 10

C. Glutamate

Question 11

What part of the eye does not contain any rods?

Answer 11

Central fovea

Question 12

W ganglion cells

Answer 12

Increased sensitivity to dim light, most excitation from rods; 40% of all ganglion cells

Question 13

X ganglion cells

Answer 13

Responsible for all color vision; 55% of all ganglion cells

Question 14

Y ganglion cells

Answer 14

Respond to rapid changes in visual image, apprise CNS when new visual event occurs; 5% of all ganglion cells

Question 15

What is the function of the lateral geniculate nucleus?

Answer 15

Receives input from the optic nerve and relays information from optic tract to visual cortex

Question 16

How much decussation occurs in the optic chiasm?

A. 50%
B. 40%
C. 25%
D. 75%

Answer 16

A. 50%

Question 17

Which layers of the LGN receive signals from the lateral half of ipsilateral retina?

Answer 17

II, III, V

Question 18

Which layers of the LGN receive signals from the medial half of opposite retina?

Answer 18

I, IV, VI

Question 19

Layers I and II of the LGN

Answer 19

Large neurons receive input from Y ganglion cells; rapidly conducting, only transmits black and white

Question 20

Layers III through VI of the LGN

Answer 20

Small to medium size neurons receiving input almost entirely from large X type ganglion cells; moderate conducting pathway for color and point-point transmission

Question 21

Transmission gating

Answer 21

Regulation of how much of the signal is allowed to pass to the visual cortex by LGN

Question 22

What are the 2 sources of gating control?

Answer 22

Corticofugal fibers from the primary visual cortex and reticular areas of the mesencephalon

Question 23

Layer IV of the primary visual cortex

Answer 23

Geniculocalcarine fibers terminate here; X signals terminate in IVcalpha, Y signals terminate in IVcbeta and IVa

Question 24

Color blobs

Answer 24

Special column-like areas receiving lateral signals from adjacent visual columns; located in secondary visual areas

Question 25

Accommodation

Answer 25

Ability of lens to adjust to near/far vision

Question 26

Accommodation in children

Answer 26

Accommodate near vision well because of the elasticity of the lens

Question 27

Suspensory ligaments around lens

Answer 27

Create tension that causes lens to remain flat under normal conditions (distant vision)

Question 28

What cranial nerve controls both sets of ciliary muscles?

Answer 28

CN III (Oculomotor)

Question 29

Meridional fibers and circular fibers

Answer 29

Components of ciliary muscles that release tension on lens, allowing for near vision

Question 30

Presbyopia

Answer 30

Decreased accommodation in old age due to the lens becoming larger, thicker, and less elastic