22. Visual system Phys

Question 1

loss of cone vision —

Answer 1

legally blind

Question 2

loss of rod vision—

Answer 2

night blindness

Question 3

what is the sensititivity and resolution associated with rods

Answer 3

high sensitivity ; low resolution

many rods converge to 1 bipolar cell (some bipolar cells interact with amacrine cells)

Question 4

what is the sensititivity and resolution associated with cones

Answer 4

best resolution, poor sensitivity

one cone to one bipolar cell

Question 5

what is the path for dark current (on center)

Answer 5

less photons stimulating photoreceptor –> cell depolarize bc more glutamate released –> onto on-center bipolar cells (mGluR6) –> increased inhibition –> close cation channels –> bipolar cell hyperpolarization –> less Glu released from bipolar –> ganglion cell

= dark

Question 6

what is path for light on on-center bipolar cells

Answer 6

increased photon –> less Glu onto on-center bipolar cell –> less inhibition –> increase cation channels open –> depolarize bipolar cells –> release glutamate onto ganglion cell

cone cells

Question 7

characteristic of mGluR6

Answer 7

Gi GPCR

when glutamate bind –> it DECREASES cation influx by closing cyclic GMP gate Na channels

(high Glu –> close channel & on-center bipolar cell inactivated)

Question 8

how do off-center bipolar cells work

Answer 8

activation of receptor in center of bipolar cell receptive field ==> hyperpolarization

use non-NMDA receptors- open and depolarizes

Question 9

what are ganglion cells

Answer 9

also on- & off- center

• have NMDA or non NMDA
• use action potential

if associated bipolar cell is depolarized –> it releases glutamate –> depolarizes ganglion cell

Question 10

what are amacrine cells

Answer 10

inhibitory - release gly or gaba

-allow vision in low light to enhance edges, shadows & contrasting areas

Question 11

lateral geniculate body

Answer 11

signals from 2 eyes are kept apart (direct target retina)

control motion of eyes to converge

control focus of eyes based on distnce

determine relative position

detect movement relative to an object

Question 12

superior colliculus

Answer 12

make visual map to activate appropriate motor responses to move eyes to intended position

coordinate head & eye movement to visual targets

Question 13

pretectum

Answer 13

reflex control of pupil/lens

send projection to edinger westphal then to ciliary ganglion

Question 14

hypothalamus job in vision

Answer 14

retinohypothalamic tract - terminate in supraoptic, suprachiasmatic & paraventricular nuclei of hypothalamus

light -dark entrainment and circadian rhythms

Question 15

medial temporal area (V5)

Answer 15

neurons that selectively to the direction of a moving edge

tract motion acress scene

ignore color

Question 16

accessory optic system

Answer 16

advanced visual processed

role in eye movement of compensation & pursuit (esp alternation w saccadic type eye movement for prolonged watching of large field motion)

Question 17

primary visual cortex (V1)

Answer 17

crude vision/general shape

-size, orientation, local direction of movement & binocular disparity

located in occipital lobe (retinotopic organization)

mostly excitatory (glutamatergic)

damage –> wont see color conscious/subconscious

Question 18

visual association cortex (v2)

Answer 18

depth perception

analyze disparity btn 2 eyes

Question 19

V3a

Answer 19

identify when motion is occuring

Question 20

V4

Answer 20

process color inputs

damage: dont see color but still see shape if diff colors are present ( subconcious level)

Question 21

ocular dominance column

Answer 21

all 6 layers of cortex

column that responds to input from one eye to other

Question 22

orientation column (V1)

Answer 22

all 6 layers

organized by visual line stimuli of varying angles

oriented perpendicular to cortical surface

Question 23

blobs V1

Answer 23

all 6 layers

sensitive to color assembles into cylindrical shape

all 3 color coding required

Question 24

achromatopsia

Answer 24

damage to specific extrastriate cortical areas

• pat is unable to see info supplied by retina

Question 25

melanopsin ganglion cells

Answer 25

intrinsically photosensitive

join rods & cones

project to suprachiasmatic nucleus of hypothalamus, nucleus of pretectum and limbic system (regulate mood)

Question 26

what is the ventral striate pathway

Answer 26

the “what” pathway

V1 - thru V2 - V4 - temporal love

-interpret images

facial recognition

selectively activated by shape, color, textrue & object recognition

Question 27

what is the dorsal striate pathway

Answer 27

“where” pathway

V1 - thru V2 & V3 - MT/V5 - parietal lobe

associate vision with movement

selectively activated by direction & speed

Question 28

agnosia

Answer 28

see an object but unable to copy/identify

inability to construct or draw visual stimuli or cant recognize picture

Question 29

prosopagnosia

Answer 29

type of agnosia

CAN recognize face, its parts and facial expression BUT CANNOT recognize whose face it is