Lecture 51 - The visual system

Question 1

what is the:

sclera

Answer 1

encapsulates the eye (laterally and caudally)

Question 2

what is the:

cornea

Answer 2

part of the sclera that is transparent in front of the eye

Question 3

what is the:

pupil

Answer 3

entry of light

Question 4

what is the:

retina

Answer 4

where light is focused (neural)

Question 5

what is the:

lens

Answer 5

focuses the light

Question 6

what is the:

ciliary muscle

Answer 6

controls lens thickness

Question 7

what is the:

iris

Answer 7

controls the amount of light entering

Question 8

what is the:

choroid

Answer 8

vascular bed surrounding the eye

Question 9

what is the:

vitreous humor

Answer 9

fills the inside compartment of the eye (between lens and retina)

Question 10

what is the:

aqueous humor

Answer 10

fills the space between the lens, iris, and cornea

Question 11

what is the:

anterior chamber

Answer 11

compartment for aqueous humor

Question 12

give steps 1 - 4 in the perception of light cascade

Answer 12

1. light enters through cornea and is refracted
2. light passes through the pupil, further refracted by the lens
3. an inverted image is projected on to the retina
4. photoreceptor cells in the retina respond to light

Question 13

what is the sensor protein in the photoreceptor

Answer 13

opsin

Question 14

give steps 5 - 8 in the perception of light cascade

Answer 14

5. photoreceptors synapse onto bipolar cells which then synapse to ganglion cells
6. signal transmitted through optic nerve to lateral geniculate nucleus
7. LGN relays visual signals to the primary visual cortex
8. visual broken down into two streams

Question 15

dorsal stream of vision refers to

Answer 15

spatial information

Question 16

ventral stream of vision refers to

Answer 16

object-related information

Question 17

if the ciliary muscles are contracted the pupil is

Answer 17

constricted

Question 18

what is the 3-component circuit of the retina

Answer 18

photoreceptors –> bipolar cells –> ganglion cells

Question 19

the inner segment of photoreceptors does what

Answer 19

ATP production and photopigment synthesis

Question 20

the outer segment of photoreceptors is composed of what

Answer 20

visual pigments in membrane discs

Question 21

summarize phototransduction in 6 steps

Answer 21

1. photon causes isomerization in rhodopsin
2. breaks apart G-protein from rhodopsin
3. activates cyclic GMP PDE
4. PDE hydrolyzes cGMP to be inactive
5. close cGMP-gated Na+ channels
6. hyperpolarization

Question 22

T/F: photoreceptors continuously secrete glutamate

Answer 22

TRUE

Question 23

T/F: glutamate is excitatory in bipolar cells

Answer 23

FALSE - inhibitory

Question 24

what decreases when photoreceptors are stimulated by light

Answer 24

glutamate production

Question 25

the decrease in glutamate results in ____ of bipolar cells

Answer 25

depolarization

Question 26

what are the properties of the rod system

Answer 26

• black and white
• high level of convergence
• high sensitivity to light
• night vision
• motion detectors

Question 27

what are the properties of the cone system

Answer 27

• color
• low level of convergence
• low sensitivity to light
• day vision
• poor motion detector

Question 28

do lateral or medial binocular ganglion cells cross

Answer 28

medial

Question 29

tapetum lucidum

Answer 29

reflective surface that intensifies vision in dim light

Question 30

tapetal degradation can occur due to

Answer 30

• nutritional induced (Zn deficiency)
• chemical-induced (zinc)
• hereditary (beagles, dilute/white hair)