Ch 17 Vision

Front 1

the retina is an outgrowth of the ______________

Back 1

diencephalon

Front 2

sclera

Back 2

-the outer layer

-white dense collagenous connective tissue

-anterior 1/6 is the transparent cornea

Front 3

Choroid

Back 3

-middle layer

-provides a route for blood supply for the outer retina

-dark layer absorbs stray light

 

Front 4

retina

Back 4

-inner layer is a transparent neural layer

-outer layer is the retinal pigment epithelium

-this is the light receptive part of the eye where the photorecepters are located

Front 5

aequous humor

Back 5

-fills the anterior part of the eye

-continuously produced by the chorid in the cilliary body

-used for support and nutrition of cornea, iris and lens

 

Front 6

how is eye shape maintained?

Back 6

-interocular pressure

Front 7

what is the route of aequous humor?

Back 7

cilliary epithelium--> pupil-->canal of schlem--> drains to venous circulation

Front 8

canal of schlem

Back 8

angle btwn cornea and irs, where aequous humor drains to

Front 9

vitreous humor

Back 9

-fills posterior eye

-made during development and never again

-single chamber that supports the globe of the eye

-rests against neural retina to help support the lens

Front 10

Glaucoma

Back 10

caused by blocked drainage of the aequous humor creates damaginf pressure on the retina, which in turn causes a loss of peripheral vision

Front 11

what are the 3 layers of the neural retina

Back 11

-outer nuclear

-inner nuclear

-ganglion cell layer

Front 12

Plexiform layers

Back 12

- contains dendrite and axons

-in each layer one cell type brings info in and one sends it out and a 3rd forms lateral connections

 

Front 13

outer plexiform layer

Back 13

here photoreceptors project to the first layer of synapses where they terminate on bipolar and horiz cells, bipolar cells project to the next layer, horizontal cells spread laterally

Front 14

horizontal cells

Back 14

spread laterally through the outer plexiform layer and interconnect photoreceptors, bipolar cells, and other horizontal cells

Front 15

where do bipolar cells terminate in the inner plexiform layer

Back 15

-on ganglion cells and amacrine cells

Front 16

ganglion cells of the neural retina

Back 16

axons leave the eye as the optic nerve

Front 17

amacrine cells of the neural retina

Back 17

in the inner plexiform layer, these cells spread latereally to connect bipolar cells, ganglion cells and other bipolar cells

Front 18

how many layers are retinal neurons and synapses arranged in? Name

Back 18

-10 layers

-retinal pigment epithelium, photoreceptor layer, outer limiting membrane, outer nuclear layer, outer plexiform layer, inner nuclear layer, inner plexiform layer, ganglion cell layer, nerve fiber layer, inner limiting membrane

Front 19

retinal pigment epithelium

Back 19

-first layer

-attached to choroid which supplies blood to outer retina & absorbs stray photons

-also supports photoreceptor layer and phagocytizes shed discs

Front 20

photoreceptor layer

Back 20

-2nd layer

-rods and cones live here, each has an inner and outer segment

Front 21

outer limiting membrane

Back 21

-acts like blood brain barrier- there is a row of intercellular junctions

-connections btwn inner segments of photoreceptor cells and support cells of the neural retina

Front 22

support cells of the neural retina

Back 22

Muller cells, a specialized glial cell

Front 23

outer nuclear layer

Back 23

contains cell bodies of photoreceptros, 3 cones (red, yellow, blue) and 1 rod

Front 24

rods and cones

Back 24

-the outer segments of both is filled with discs

-the main protein of the outer segment of the membrane is visual pigment, because the visual pigment is located int he outer segment this is the pt of visual transduction

-inner segment of rods and cones contain mitochondria

Front 25

rhodopsin

Back 25

visual pigment found in the outer membrane of rods

Front 26

visual transduction

Back 26

-photons absorbed in the outer segment of rods and cones elicit a receptor potential that then spreads to the rest of the cell

Front 27

outer plexiform layer

Back 27

- 5th layer

-connections btwn photoreceptors and bipolar and horiz cells

Front 28

inner nuclear layer

Back 28

-6th layer

-cell bodies of retinal interneurons

Front 29

bipolar cells

Back 29

-for direct signalling btwn photoreceptors and ganglion cells

-are specific for rods/cones

-types for light turning on and light turning off

Front 30

inner plexiform layer

Back 30

-7th layer

-connections btwn biplar and amacrine cells and ganglion cells

Front 31

ganglion cell layer

Back 31

-8th layer

-cell bodies of out put neurons of neural retina, have on and off subtypes. axons form optic nerve

Front 32

nerve fiber layer

Back 32

-9th layer

-axons of ganglion cells converge at optic disc

-also a route for central retinal branch of opthalmic artery--> supplies blood to inner retina

Front 33

inner limiting membrane

Back 33

-10th layer

-thin basil lamina btwn proximal endings of Muller cells and vitreous humor

Front 34

optic disc

Back 34

-exit of axons from ganglion cells of eye

-area of no photoreceptors or other retinal neurons

-creates a non-percieved blind spot

Front 35

macula lutae

Back 35

area of high conventration of cones

Front 36

fovea

Back 36

-only cones

-in line with the visual axis

-high visual acuity at the center of the macula

-all neurons an capillaries are collected around the edges of the fovea

-light doesn't have to filter thru transparent  retina  to reach photoreceptors

Front 37

receptive field

Back 37

specific space that is responsive to stimulus, in vision the part of the outside world that falls on the retina, specifically the bipolar and ganglion cells

Front 38

convergence

Back 38

many cells synapsing on one cell

Front 39

divergence

Back 39

single cells synapsing on many cells

Front 40

phototransduction (name 5 steps)

Back 40

1. retinal changes from cis to trans configuration

2. trans retinal dissasocaites from opsin, thereby activating it

3.active opsin activates G-protein (transducin)

4. Tranducin activates phosphodiesterase that hydrolyzes cGMP

5. reduced concentration of cGMP leads to closure of Na+ channels which causes hyperplaeization

Front 41

photorecptors detect _____________.Therefore they depolarize and release more neurotransmitter when in ______________ conditions.

Back 41

dark

Front 42

What happens to rods in light vs dark conditions?

Back 42

dark conditions cause depolarization, Ca2+ channels open to release bunches of NT the NT has an inhibatory effect at the bipolar cell and therefore no ESPS are created between the bipolar cell and the gnaglion cell and AP fail to propropogate along the optic nerve

Front 43

rods

Back 43

-respond to light less than moonlight

-act slowly

-require much convergence to yield a weak signal, this leads to lack of detail and poor spatial resolution

Front 44

cones

Back 44

-respond to daylight

--act quickly to produce stronger signals with less convergence--> sharp images and fine spatial details

Front 45

intensity of illumination is ____ as important as _____________ btwn different areas of the receptive field

Back 45

NOT, contrast

Front 46

receptive fields of the ganglion cells have 2 zones of concentric  circular areas, these are___________.

Back 46

2

-stim of center causes an increase or decrease  in the cell's activity

-stimulation of the peripheral area causes the opposite effect

Front 47

on center set ups

Back 47

-stim by light hitting the center of the field & inhibited by light hitting the periphery

Front 48

off center set ups

Back 48

stim by light hitting the periphery and inhib by light hitting the center

Front 49

why do on and off center set ups respond differently?

Back 49

their are different receptor types for glutamate in the on and off fields

Front 50

every point in the visual field has what type of ganglions?

Back 50

both on and off center

Front 51

stim the surround has the ______________ effect of stim the center

Back 51

opposite

Front 52

what combination  ganglion cell activation produces the greatest activity?

Back 52

stim of on-center with light and the on-surround without light

Front 53

what combination  ganglion cell activation produces the least activity?

Back 53

stim of on-center without light and the on-surround with light

Front 54

what combination  ganglion cell activation essentially cancels the other out?

Back 54

stim of on-center with light and on-surround with light

Front 55

where do retinal ganglion cells output too

Back 55

-LGn and then to visual cortex for consious vision

-superior collic for tracking and visual refelexes

-others including the supraoptic and suprachiasmatic nuclei of the  hypothalm

Front 56

what are the only projection cells from the retina?

Back 56

ganglion, they leave via CN II

Front 57

each optic tract contains the fibers from the ___1__ temporal retina and ___2___ nasal retina

Back 57

1. I/L

2. C/L

Front 58

what allows for depth perception?

Back 58

comparison btwn right and L, lesions cause comparable deficits in both eyes

Front 59

why are the areas of fovea and macular disproprtionately represented in the visual system?

Back 59

-both are importand areas for focusing and need  more cells per area

-they have smaller bipolar and gang cells

-more direct pathways with minimal visual processing

Front 60

describe the pathway for visual stimuli, retina to cortex

Back 60

neural retina--> optic nerve--> optic chiasm-->optic tract--> LGN--> optic radiation of the retrolenticular/sublenticular limb of IC --> calcerine sulcus (1* visual cortex)

Front 61

superior visual space

Back 61

-fibers from the inf retina

-travel thru temporal lobe

-damage here causes vision loss

-project inf to calcerine sulcus

Front 62

inferior visual space

Back 62

-fibers from superior retina

-travel thru sup radiation

-projects sup to calcerine sulcus

Front 63

central representations of space

Back 63

-from macular fibers

-carried B/L

-either entire area must be compromised or central vision space is spared

-posterior of calcerine sulcus

Front 64

peripheral fields

Back 64

represented anteriorly to calcerine sulcus

Front 65

1* visual cortex processess

Back 65

contrast info and visual orientation

Front 66

visual association areas process

Back 66

form, color and motion input from 1* visual cortex

Front 67

processing in temporal and parietal lobes?

Back 67

-temporal- ID of objects

 -parietal (and post central gyrus)-spatial localation of obj

- info sent to assoc areas is for more complex pattern recognition

Front 68

modules of 1* visual cortex

Back 68

-recieves info from 1 area of C/L visual field (small area for foveal parts, large area for peripheral parts)

-composed of cloumns of neurons that respond best to a specific stimuli conveyed from one eye (ocular dominance) to another (eg depth, motion and orientation)

-nearby columns eval similar info

-interspersed among columns are cells sensitive to color

Front 69

parallel processing

Back 69

because info is divided into component elements, eg color.

-this type of processing is FAST

Front 70

superior colliculi

Back 70

a seondary pathway of visual processing thought to play a role in visual refleses and eye movement

Front 71

pre-tectal nuclei

Back 71

a secondary pathway of visual processing involved with the pupillary light reflex--> projects B/L to Ediger Westfall

Front 72

pupillary light reflex

Back 72

-shine a bright light in one eye and both pupils constrict, same eye direct pupillary light reflex, C/L eye, consensual pupillary light reflex

-no cortical connections involved

-lesions of optic and oculomotor can be obseved

Front 73

pathway of pupillary light reflex

Back 73

retina--> CN II--> pre-tectal area to egindger --> B/L CN III back towars eye and gandglion that synapses with the musles of the cilliary body

Front 74

how are visual deficits named?

Back 74

by parts of the visual field lost

Front 75

anopsia

Back 75

visual deficit usually 1 or more quarters of the visual field

Front 76

homonymous

Back 76

similar visual field losses in both eyes

Front 77

heteronymous

Back 77

-different visual field losses in each eye

 

Front 78

damage at chiasm-- what's affected?

Back 78

-damage to ant chiasm only affects I/L eye

-at chiasm heteronymous

-behind chiasm homonymous

Front 79

lesions of the optic nerve

Back 79

-blindness of I/L eye

-most of visual field is maintained due to C/L eye

Front 80

Lesion of lateral optic chiasm (non-crossing lat fibers)

Back 80

-nasal hemianopsia of I/L eye

-retain most visual space, may notice if eye of damage tract is closed

-caused by lat pressure on one side of chiasm; aneurism on internal carotid artery

Front 81

Lesion of the optic chiasm

Back 81

B/L hemianopsia

Front 82

lesion of the optic tract

Back 82

-C/L homonymous hemianopsia

-loss of complete half of visual space, usually you only lose a quadrant

Front 83

lesions of optic radiations

Back 83

-C/L homonymous quadrantanopsia

-lesion of inf fibers causes homonymouse superior quadrantanopsia

Front 84

lesions of the optic lobe

Back 84

-C/L homonymous hemianopsia

-due to blockage of the post cerebral artery

-usually some central (macular) sparing

Front 85

focus aka accomodation

Back 85

-done via lens by stands connected to cilliary muscles

 

Front 86

contraction of cilliary muscles

Back 86

allows strands to go slack, the lens to fatten

-good for near viewing

Front 87

relaxation of cilliary muscles

Back 87

-strands taut

-lens thin

-see far away

 

Front 88

how do corrective lenses work?

Back 88

they change how light enters the eye, if you are near sighted it brings the image back, if you are farsighted it brings the image fwd

Front 89

what 3 things happen when you focus on near objects?

Back 89

1. convergence- both eyes gaze at the same place

2. accomodation- focal length changes for optimal viewing

3. pupillary restriction reduces abberations  and  increases depth of focus, this action involves the cerebral cortex

Front 90

near reflex (aka accomodation reflex)

Back 90

-axons from retina project B/L to LGN

-goes to visual cortes, visual assocaition cortex, superior colliculus, oculomotor nerve, CN III projects back to eye to synapse in cilliary gang, post gang fibers innervate iris muscles

Front 91

corneal reflex

Back 91

-touch cornea of one eye, both eyes blink

-main sensory of trigem-->interneurons (MLF)-->facial motor N --> facial nerve to obicularis oculi