Visual System Physiology

Question 1

what are the photoreceptor cells connected to?

Answer 1

bipolar cells

Question 2

what are bipolar cells connected to?

Answer 2

ganglion cells

Question 3

the central processes coming off the ganglion cells form what?

Answer 3

the axons of the optic nerve which eventually end up in the nuclei of the brain

Question 4

which system is heavily dependent on convergence?

Answer 4

rod system

Question 5

why is convergence important in the rod system?

Answer 5

it allows the rod system to operate in dim light

Question 6

where does the density of the cones peak at?

Answer 6

the fovea

Question 7

where does the density of the rods peak at?

Answer 7

about 20 degrees to the side of the cones

Question 8

what happens to the photoreceptor cells under dark conditions?

Answer 8

they depolarize

Question 9

what happens to the photoreceptor cells under light conditions?

Answer 9

they hyperpolarize

Question 10

what are rods and cones constantly releasing?

Answer 10

glutamate

Question 11

when is glutamate release from the photoreceptor cells the highest?

Answer 11

when it is dark

Question 12

when is glutamate release the lowest?

Answer 12

when there is light

Question 13

when does glutamate act as an excitatory amino acid?

Answer 13

when the receptor is an NMDA or non-NMDA receptor

Question 14

when does glutamate act as an inhibitory amino acid?

Answer 14

when the receptor is an mGlu6 receptor

Question 15

what glutamate receptor do bipolar cells express?

Answer 15

mGlu6 receptor

Question 16

what does the mGlu6 receptor do when it is activated?

Answer 16

it closes the cGMP-gated Na+ channel

Question 17

what happens when the bipolar cell is activated?

Answer 17

it releases glutamate

Question 18

what glutamate receptor is found on the ganglion cells?

Answer 18

NMDA or non-NMDA (so glutamate will act as an excitatory amino acid on the ganglion cells)

Question 19

what is the most prominent target of the retina?

Answer 19

the lateral geniculate body

Question 20

what is the role of the lateral geniculate body?

Answer 20

it regulates the flow of information to the primary visual cortex

Question 21

what is the role of the superior colliculus?

Answer 21

it creates a map of the visual space to activate appropriate motor responses required to move the eyes

Question 22

what does the superior colliculus connect with?

Answer 22

connects with the tectospinal tract to send projections to cervical anterior horn cells

Question 23

what is the pretectum important for?

Answer 23

the pupillary light reflex

Question 24

what does the pretectum send projections to?

Answer 24

the edinger-westphal and then on to the ciliary ganglion

Question 25

what are the small number of fibers that branch off the optic tract known as?

Answer 25

the retinohypothalamic tract

Question 26

where do the fibers of the retinohypothalamic tract terminate?

Answer 26

in the supraoptic, suprachiasmatic and the paraventricular nuclei of the hypothalamus

Question 27

visual input to the hypothalamus drives what?

Answer 27

the light-dark entrainment of the neuroendocrine function and other circadian rhythms

Question 28

what is the role of the accessory optic nuclei?

Answer 28

advances visual processing

Question 29

what are 4 functions of the lateral geniculate nucleus?

Answer 29

control the motions of the eyes-to converge on a point of interest, control the focus of the eyes based on distance, determine relative position of objects to map them in space, detect movement

Question 30

what are the projections from the LGB to the visual cortex known as?

Answer 30

optic radiations

Question 31

what 3 areas make up the visual cortices?

Answer 31

primary visual cortex, parastriate cortex, and extrastriate cortex

Question 32

what is the major job of V1?

Answer 32

to identify the edges and contours of objects

Question 33

what is area V2 important for?

Answer 33

depth perception, which is detected by analyzing the disparities between the two eyes

Question 34

what is the major function of area V3a?

Answer 34

identification of motion

Question 35

what is the major function of V4?

Answer 35

complete processing of color inputs

Question 36

what are lesions in the V4 area known to cause?

Answer 36

achromatopsia- dullness in color

Question 37

what are the MT/V5 areas important for?

Answer 37

tracking motion across a scene in terms of directionality and context of the background

Question 38

what are the ocular dominance columns?

Answer 38

a slap of cells that preferentially respond to input from one eye or the other

Question 39

what are the orientation columns?

Answer 39

an organized region of neurons that are excited by visual line stimuli of varying angles

Question 40

where are the orientation columns located?

Answer 40

perpendicular to the cortical surface

Question 41

what are the blobs in the primary visual cortex?

Answer 41

an organized region of neurons that are sensitive to color assembled into cylindrical shapes

Question 42

what type of ganglion cells can directly sense light?

Answer 42

melanopsin ganglion cells

Question 43

what are the melanopsin ganglion cells sensitive to?

Answer 43

blue-wavelengths of light

Question 44

where do the melanopsin ganglion cells project directly to?

Answer 44

they project directly to hypothalamic suprachiasmatic nucleus

Question 45

what is the suprachiasmatic nucleus?

Answer 45

it is the neuroendocrine effector in the pineal gland which produces melatonin in a rhythmic pattern

Question 46

what is the general pathway of the dorsal pathway of the visual system?

Answer 46

from the primary visual cortex to the parietal/frontal cortex

Question 47

what is the dorsal pathway important for?

Answer 47

associating vision with movement and completing motor acts based on visual pathway

Question 48

what is the dorsal pathway laid out?

Answer 48

V1--> V2/V3--> V5/MT--> parietal lobe

Question 49

what is the general pathway of the ventral pathway?

Answer 49

primary visual cortex to the inferior temporal cortex

Question 50

what is the ventral pathway primarily responsible for?

Answer 50

interpreting images (recognizing human symbols, copying forms, facial recognition)

Question 51

what is the ventral pathway laid out?

Answer 51

V1--> V2--> V4--> temporal lobe