L7: Vision II

Question 1

layers of the retina

Answer 1

photoreceptors
horizontal cells
bipolar cells
amacrine cells
ganglion cells

Question 2

rods and cones interact w/ ______ cells via NT ?

Answer 2

bipolar cells

glutamate

Question 3

amacrine cell NTs

Answer 3

8 or more kinds
including:
GABA, glycine, dopamine, ACH, indolamine

**note all are inhibitory

Question 4

retinal layer - photoreceptors

Answer 4

rods and cones
transmit signals to outer plexiform layer

synapse w/ bipolar cells and horizontal cells

Question 5

plexiform layer = ?

Answer 5

layer of synaptic connections

Question 6

horizontal cells

Answer 6

1. transmit signals from rods/cones to bipolar cells
2. transmit signals to outer plexiform layer
3. output is always inhibitory — lateral inhibition

Question 7

bipolar cells

Answer 7

1. transmit signals from rods/cones and horizontal cells
2. transmit signals to inner plexiform layer
3. synapse w/ amacrine and ganglion cells

Question 8

amacrine cell signals

Answer 8

transmit signals to :
–directly from bipolar to ganglion cells

—w/in inner plexiform layer from axons of bipolar cells to dendrites of ganglion cells or to other amacrine cells

Question 9

ganglion cells

Answer 9

transmit signals from retina to brain**

axons make up optic nerves**

Question 10

axons of the optic nerve

Answer 10

only retina cells that transmit action potentials

Question 11

interplexiform cells

Answer 11

transmit from inner plexiform to outer layer (retrograde signals)

inhibitory signals – lateral inhibition

Question 12

foveal region

Answer 12

cone vision

3 neurons in direct pathway

Question 13

3-neuron cone vision

Answer 13

cones
bipolar cells
ganglion cells

Question 14

4-neuron rod vision

Answer 14

rods
bipolar cells
amacrine cells
ganglion cells

Question 15

describe amacrine cells

Answer 15

• -30 kinds
• -dif type does dif things
  ex. rod conduction, continuing visual signals, offset of visual signals, dark or light vision, mvt

Question 16

because of their various functions, amacrine cells are ?

Answer 16

interneurons

help analyze visual signals before they leave retina

Question 17

describe ganglion cells

Answer 17

~60 rods and 2 cones per ganglion cell to optic nerve fiber

Question 18

approaching the fovea, ____ rods and cones converge on each optic fibers, rods and cones also become more ______ .

Answer 18

fewer
slender

central fovea – only cones ~35k

Question 19

what is the result of rods and cones sliming down

Answer 19

increases visual acuity in central retina

Question 20

describe peripheral retina

Answer 20

–more sensitive to low light

up to 200 rods converge on a single optic fiber in periphery

Question 21

types of ganglion cells

Answer 21

3 types

W, X, Y

Question 22

W ganglion cells

Answer 22

40% of ganglion cells
small
transmit 8 m/sec

most excitation due to rods by way of small bipolar and amacrine cells

Question 23

W ganglion cell in periphery

Answer 23

broad fields in peripheral retina

because dendrites spread widely in inner plexiform layer

Question 24

X ganglion cells

Answer 24

55% of ganglion cells
medium size
transmit 14 m/sec

Question 25

X ganglion cell signals

Answer 25

small fields -- discrete retinal locations every x ganglion receives input from at least one cone cell

Question 26

cells probably responsible for all color vision

Answer 26

x ganglion cells

Question 27

Y ganglion cells

Answer 27

5% large transmit 50 m/sec and up respond to rapid changes in visual image

Question 28

Y ganglion to CNS

Answer 28

transmit almost instantly when a new visual event occurs anywhere in the field but w/o great accuracy w/ respect to location

Question 29

dorsal lateral geniculate nucleus

Answer 29

receives input from optic nerve (in thalamus) relays info from optic tract to visual cortex by optic radiation = geniculocalcarine tract

Question 30

decussation in optic chiasm

Answer 30

50%

Question 31

layers of lateral geniculate nucleus

Answer 31

6 layers 2,3,5 = receive signals from lateral half of ipsilateral retina 1,4,6 = from medial half of opposite retina

Question 32

layers 1 and 2

Answer 32

magnocellular layer large neurons input almost entirely from Y ganglion provide rapid conduction only black and white

Question 33

layers 3 and 4

Answer 33

parvocellular layers small/medium neurons input from X ganglion moderate conduction color

Question 34

describe transmission gating

Answer 34

the lateral geniculate nucleus controls how much of the signal is allowed to pass to the cortex

Question 35

source of gating control

Answer 35

corticofugal fibers from primary visual cortex reticular areas of mesencephalon

Question 36

describe sources of gating control

Answer 36

both sources are inhibitory and help highlight visual info that is allowed to pass

Question 37

the primary visual cortex is also called ?

Answer 37

striate cortex

Question 38

characteristics of primary visual cortex

Answer 38

in occipital lobe 6 distinct layers geniculocalcarine fibers terminate in layer 5

Question 39

where do signals from macular area terminate in visual cortex?

Answer 39

signals from macular area terminate near occipital pole

Question 40

where do peripheral retina signals terminate in visual cortex?

Answer 40

term in concentric half circles anterior to the pole but still along the calcarine fissures

Question 41

layer 4 of primary visual cortex

Answer 41

organized into subdivisions 4calpha = signals from Y ganglion 4cbeta and 4a = signals from x ganglion

Question 42

the primary visual cortex is organized into several million vertical ______ of ______.

Answer 42

columns of neurons 30 - 50 micrometer diameter ~1000 neurons per column

Question 43

describe color blobs

Answer 43

special column-like areas --located among the columns of 2ndary visual areas receive lateral signals from adjacent visual columns are activated specifically by color signals

Question 44

signals from the 2 separate eyes enter _______ stripes of columns in layer ___.

Answer 44

alternating stripes | layer 4

Question 45

what does the cortical area do?

Answer 45

deciphers whether the respective areas of the 2 visual images from each eye register w/ each other

Question 46

accommodation in children

Answer 46

refractive power of the lens can be voluntarily increased from 20 to 34 diopters accommodation of 14

Question 47

accommodation in young person -- relaxed state

Answer 47

no tension on capsule | lens assumes almost spherical shape

Question 48

accommodation in young person -- normal eye conditions

Answer 48

suspensory lig. attached radially around lens create tension causes lens to remain flat

Question 49

meridional fibers

Answer 49

part of ciliary muscle | contract and release tension on lens

Question 50

circular fibers

Answer 50

part of ciliary muscle | decrease tension on lens

Question 51

_______ controls both sets of ciliary muscles

Answer 51

CN III | optic nerve

Question 52

accommodation in older person

Answer 52

lens is larger and thicker w/ age less elastic accommodation power decreased by 2 diopters by 50 decreased to 0 by 70

Question 53

define presbyopia

Answer 53

farsightedness due to loss of elasticity of the lens occurs typically in middle to old age **need for reading glasses