Special Senses - Vision Flashcards Preview

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Flashcards in Special Senses - Vision Deck (82):
1

If an object is far away, light rays have_____ and _____ rays enter the eye. Does or does not need a lot of refraction.

diverged
only parallel
does not need a lot of refraction

2

If an object is near, light rays are_____. Need ________refaction to make the rays focus on the retina.

still diverging
more refraction

3

To focus an image on the retina, the eye uses

refraction

4

two sights of refraction

cornea and lens

5

cornea role in refraction

1st site of refraction
bends light the most of any structure (2/3 of the bending)
the amount of bending is fixed - we can't control it

6

why do we need the variable refection provided by the lens

so we can see near things and farthings

7

Accommodation requires what 3 components

ciliary muscle, suspensory ligaments, the lens itself

8

Near vision requires ______ of the ciliary muscle

contraction.

9

when ciliary muscle contracts, the tension on suspensory ligaments ______ . The lens becomes _____

is released.
rounder

10

increasing the curvature of the lens ______ the refractive power of the lens

increases. allows the light rays from a nearby object to be bent sufficiently to bring them into focus on the retina

11

In young children, the lens can add ____ diopters, in the mid 20s, a loss of _____ results in a strength of ___ diopters. By 50s, the lens may be able to add only ____ diopters

20
elasticity
10
1

12

Far vision requires ______ of the ciliary muscle

relaxation

13

when the ciliary muscle relaxes, the tension on suspensory ligaments ______. The lens becomes _______.

increases
flat

14

decreased curvature of the lens _____ refractive power of the lens

decreases. if the object is far away, less bending of the parallel light rays is required, the lens needs to be flatter.

15

The near response includes (3)

contraction of ciliary muscles
convergence of eyes to point of focus
constriction of pupil

16

constriction of the pupil in the near response does what

reduces the opening for light to enter, eliminating some diverging light rays - this allows us to focus better.

17

In the retina, light moves from ____ to _____

the inner limiting membrane to the pigment epithelium through multiple layers of cells

18

in the retina there are multiple cell types (5)

photoreceptor cells
bipolar cells
ganglion cells
horizontal cells
amacrine cells

19

Light passes through all of the layers of cells (except RPE). as a result, there is

distortion of the image that the retina will take care of

20

Vertical pathway of the retina is composed of (3)

photoreceptor
bipolar cell
ganglion cell

21

The vertical pathway is the pathway for

relaying visual information to the brain

22

The circuit for the _____ seems to be the base for all vision

cones

23

photoreceptors have a constant release of ____

glutamate

24

in the dark - photoreceptor release of glutamate is _____

high

25

when a photon activates photoreceptor, release of glutamate is______

low (remember that light hyper polarizes the rods and cones)

26

Vertical pathway for cones

1. light hits a photoreceptor
2. photoreceptor is hyperpolarized => decreased release of NT (glutamate) onto a bipolar cell

27

On-center bipolar cell

activation of photoreceptor (decrease glutamate to center of cell) in CENTER of bipolar cell's receptive field causes DEPOLARIZATION of the bipolar cell.

activation of photoreceptor (decreased glutamate to periphery) in the SURROUNDING region causes HYPERPOLARIZATION of the bipolar cell

28

Off- center bipolar cell

activation of photoreceptor (decreased glutamate to periphery) in the SURROUNDING region causes DEPOLARIZATION of the bipolar cell

activation of photoreceptor (decreased glutamate to center of cell) in CENTER of bipolar cell;s receptive field causes HYPERPOLARIZATION of the bipolar cell

29

When a photoreceptor is activated, where does depolarization occur in an on center bipolar cell as compared to an off center bipolar cell>

the center
the periphery

30

if a photoreceptor activates an on center bipolar cell, what type of receptor are we thinking

metabotropic

31

if a photoreceptor activates an off center bipolar cell, what type of receptor are we thinning

AMPA

32

On-center bipolar cell mechanism

metabotropic receptor
NT binding the receptor (DARK) causes a DECREASE in cation influx

so… in the dark, the on-center cell is hyper polarized

with light, photoreceptor releases LESS glutamate, so cation current increases and the on center cell is depolarized

33

Off-center bipolar cell mechanism

AMPA receptor
NT binding the receptor (DARK) causes an INCREASE in cation influx

so… in the dark, the off-center cell is depolarized

with light, photoreceptor releases LESS glutamate, so cation current decreases and the off center cell is hyper polarized

34

Ganglion cells are also On-center and off-center based on

whatever their connection bipolar cell is

35

When bipolar cells are depolarized, they release what NT

glutamate

36

bipolar cells, when depolarized, release glutamate onto what cells

ganglion cells.

37

Ganglion cell axons become

the fibers of the optic nerve

38

The first place in the eye we see true action potentials is

the ganglion cells.

39

Ganglion cells rely on _____ as NT

glutamate

40

Describe the vertical pathway for rods

many rods converge on one ON-center bipolar cell
bipolar cell synapses on an A11 amacrine cell
A11 amacrine cell synapses on a cone ON-center bipolar cell
the cone on-center bipolar cell activates a ganglion cell

41

Rods do vision in ______ situations

low light

42

need many rods to converge on a _______. WHy>

bipolar cell. to increase our chances of seeing what we need to see.

43

Role of on and off center cells

these two types of cells help us increase the ability to detect edges and sharpen our vision

44

on center cells tell us

where something is

45

off center cells tell us

where something ends.

46

amacrine cells and horizontal cells

provide inhibitory signals that modify the activity of neighboring photoreceptors, bipolar cells or ganglion cells

47

Action potentials occur in what cells

ganglion cells

48

axons from ganglion cells will become

fibers of the optic nerves

49

the retina from each eye sees ______ visual fields

two different

50

The Left temporal retina is activated by light coming from

the right visual field

51

the right nasal retina is activated by light coming from

the right visual field

52

the right temporal retina is activated by light coming from

the left visual field

53

the left nasal retina is activated by light coming from

the left visual field

54

at the _____ the axons from the ______ retina on each side will cross and join the axons from the _____retina

optic chiasm
nasal retina
temporal retina

55

Crossing at the optic chiasm allows what

all of the information from one visual field to be sent to the same part of the brain (the side opposite the visual field)

56

after the axons cross at the optic chiasm, they synapse where

lateral geniculate body

57

cells in the LGN are of what type

on and off center as well

58

functions of the LGN (4)

1. control motions of the eyes - so they converge on the desired point of interest
2. control focusing - so that the image we are interested in is in the best focus possible
3. identify major elements within our visual image - send that info to the cortex
4. identify motion

59

The neocortex is divided into ____ layers of cells

6

60

Primary visual cortex =

V1

61

layers 1, 2, 3 allow

networking between V1 and other parts of the cortex

62

layer 4

receives inputs from the LGN

63

Layers 5 and 6

send information back to the LGN

64

cortex is divided from a functional standpoint into

columns

65

each column does _____
neighboring columns have _____

a different job
related jobs

66

There are a lot of columns in V1 that receive input from photoreceptors in the macula

in part bc that is the place where receptor density is the greatest

67

peripheral regions of the retina have much less area in V1 devoted to them

few receptors, many of which converge onto the same bipolar cells

68

MAJOR JOB OF V1

identify edges/contours of the components in visual image

69

MAJOR JOB of V2

identify disparities in the visual images presented by the two eyes - gives us depth perception

70

Color vision in V1 is done by

blobs

71

accurate color detection depends on input from

all three sets of cones

72

_____ kinds of cones are triggered by any bright light

all three kinds of cones, because of the overlap in the sensitivities of opsins. certain types will just be activated more

73

how does the brain arrive at color perception

uses the overlapping activity of the opsins

74

MAJOR JOB of V4

complete processing of the color inputs

75

without higher processing of the visual image, we could reconstruct the visual image but not

name the image
copy the image
aim at the object in the image
recognize husband/wife/father/mother
we must rely on other areas of the cortex to interpret why the primary visual cortex and associated areas have done so far

76

Dorsal pathway - think

motor

77

Dorsal pathway - explained

the dorsal pathway leaving the occipital cortex relays information to the motor cotices and enables us to complete motor acts based on visual input - allows you to play catch

78

Ventral pathway - think

recognition

79

Ventral pathway - explained

the ventral pathway relays visual info to areas of the brain involved in higher processing of sensory inputs. The integration of visual input with other sensory input allows us to use that visual image to accomplish higher order functions, including naming the object and copying the object

80

copying an object and naming/recognizing it are _____functions. damage to the temporal lobe can

separate
selectively impair one without hindering the other

81

Similar or related objects are all coded for in

localized regions of the temporal lobe

82

there is a specialized area for _________ (implications in autism)

recognizing human faces.