visual system

Question 1

the eye is a fluid filled sphere enclosed by what 3 layers of tissue (what is their order from outermost to innermost)

Answer 1

sclera (outermost), choroid (intermediate) and retina (innermost)

Question 2

what are the 2 fluid compartments of the eye

Answer 2

aqueous humor and vitreous humor

Question 3

describe aqueous humor (where, consistency, function)

Answer 3

in ant chamber
watery liquid
supplies nutrients to surrounding structures

Question 4

describe vitreous humor (where, consistency, function)

Answer 4

fills space btw back of lens and retina
thick gelatinous substance
maintains shape of eye and supplies nutrients to surrounding structure

Question 5

what is the sclera

Answer 5

white fibrous tissue forming the outermost layer of the eye

Question 6

what does the sclera become in front of the eye

Answer 6

cornea

Question 7

what is the cornea

Answer 7

transparent tissue that separates and protects ere from external environment and allows light rays into the eye

Question 8

what is the choroid

Answer 8

capillary bed that nourishes retinal cells

Question 9

whats the ciliary body and what two parts does it have to it

Answer 9

a ring of tissues that encircles the lens and consists of a muscular (ciliary m.) and vascular part (ciliary processes)

Question 10

whats the function of the ciliary muscle and what connects it to the lens

Answer 10

controls the shape of lens
Zonule fibers

Question 11

whats the function of ciliary processes

Answer 11

produces aqueous humor in ant chamber

Question 12

whats the iris, what does it contain and whats their function

Answer 12

colored portion of the eye seen thru cornea
contains 2 sets of m. that contract and adjust size of pupil

Question 13

what does the lens do

Answer 13

it refracts light rays coming into eye and generates a focused image on the surface of the retina

Question 14

what does accommodation of the lens mean and what part of the eye does these accommodations

Answer 14

dynamic changes in refractive power of the lens to form a shape image on the retina
done by contraction of ciliary m.

Question 15

what accommodation of the lens is done for distant vision

Answer 15

lens becomes thin and flat, less refractive power

Question 16

what accommodation of the lens is done for near vision

Answer 16

lens becomes thick and round, more refraxctive power

Question 17

where is the image focused in emmetropia

Answer 17

right on the retina (normal eye)

Question 18

describe myopia (how does the lens accommodate, where is the image, hard to see what, corrected by what)

Answer 18

lens doesn’t accommodate enough
image is in front of retina
hard to see distant objects
corrected by converging (convex) glasses

Question 19

describe hyperopia (how does the lens accommodate, where is the image, hard to see what, corrected by what)

Answer 19

lens over accommodates
image is focused beyond the retina
hard to see nearby objects
corrected by diverging (concave) glasses

Question 20

the retina is considered to be part of what

Answer 20

the nervous system

Question 21

what is the retina’s function

Answer 21

it contains neurons that are sensitive to light, and convert visual info to electrical signals and transmit it to the brain

Question 22

what are the 2 photoreceptor neurons

Answer 22

rods and cones

Question 23

describe rods (shape, number, location in retina, luminosity level, vision accuracy, photosensitive pigments, type of cell, color vision)

Answer 23

shape: rod-shaped (rectangular head)
number: 120 millions
location in retina: periphery
luminosity level: dim light (highly sensitive to light)-night vision
vision accuracy: low resolution
photosensitive pigments: rhodopsin (found in carrots)
type of cell: 1: monochromic (absorb white color)
color vision: no

Question 24

describe cones (shape, number, location in retina, luminosity level, vision accuracy, photosensitive pigments, type of cell, color vision)

Answer 24

shape: cone-shaped (triangular head)
number: 8 millions
location in retina: center (fovea)
luminosity level: bright light (low sensitivity to light)- day vision
vision accuracy: high resolution
photosensitive pigments: iodopsin, porphyropsin, cyanopsin
type of cell: 3 types; S-cones (blue), M-cones (green), L-cones (red)
color vision: yes

Question 25

what are the 5 classes of neurons of the retina

Answer 25

photosensitive bipolar cells ganglion cells horizontal cells amacrine cells

Question 26

what forms the optic nerve

Answer 26

axons of the ganglion cells

Question 27

what cells regulate the activity of photosensitive neurons

Answer 27

horizontal cells

Question 28

what cells are the lateral communication between neurons

Answer 28

amacrine cells

Question 29

what is the electrical activity of photosensitive and retinal neurons for dark light

Answer 29

dark light --> cone cell depolarized --> bipolar cell hyperpolarized (active inhibition) --> ganglion cell hyperpolarized (passive inhibition) --> no info transmitted to the brain

Question 30

what is the electrical activity of photosensitive and retinal neurons for light light

Answer 30

light --> cone cell hyperpolarized --> bipolar cell depolarized --> ganglion cell depolarized --> info transmitted to the brain

Question 31

what are the 2 classes of ganglion cells (what are they active and silent to)

Answer 31

on-center cells: active to light spot in center and silent to dark spot in center off-center cells: silent to light spot in center and active to dark spot in center

Question 32

what other type of cell as on and off-center cells

Answer 32

bipolar cells

Question 33

the activity of on-center and off-center ganglion cells are controlled by what and what behavior do these interractions determine

Answer 33

multiple interractions btw photosensitive cells, bipolar cells and horizontal cells center-surround behavior

Question 34

what cells regulate the amount of transmitter that the photosensitive cells release onto bipolar cell dendrites

Answer 34

horizontal cells

Question 35

how is an image projected on the retina

Answer 35

inverted top to bottom and revered R to L

Question 36

the visual field is divided into what

Answer 36

2 hemifields: R and L hemi field

Question 37

the R visual hemi-field is seen by what type of retina

Answer 37

right nasal and left temporal retinas

Question 38

the L visual hemi-field is seen by what type of retina

Answer 38

left nasal and right temporal retinas

Question 39

what is the name of when visual fields of both eyes overlap in the central portion of visual field

Answer 39

binocular visual field

Question 40

what % of optic n. fibers cross at the optic chiasm and what % stay on the same side

Answer 40

60% contralateral 40% ipsilateral

Question 41

what retina fibers project to contralateral side

Answer 41

fibers fron nasal retina

Question 42

what retina fibers project to ipsilateral side

Answer 42

fibers fron temporal retina

Question 43

after the optic hciasm, what do the optic fibers form

Answer 43

optic tract

Question 44

where do the majority of the optic fibers terminate

Answer 44

Lateral geniculate body in the thalamus

Question 45

what do neurons from the LGB form and where do they terminate

Answer 45

optic radiation and they terminate in the striate cortex

Question 46

where do axons of the ganglion cells also project in the midbrain

Answer 46

hypothalamus, pretectum, sup colliculus

Question 47

function of hypothalamus

Answer 47

reg of circadian rhythm (biological clock)

Question 48

function of pretectum

Answer 48

control of pupillary light reflex

Question 49

function of sup colliculus

Answer 49

orienting the mvts of head and eyes

Question 50

what are the other names for visual cortex

Answer 50

striate cortex, primary visual cortex, V1, Brodmann's area 17

Question 51

what does the visual cortex process (give examples)

Answer 51

basic sensory info sent by retina examples: place back inverted image to og position, binocular vision, 3D image, ...

Question 52

what representation in the visual cortex does the central region (macula, fovea) of the retina have

Answer 52

a large representation

Question 53

what is called the 6 cellular layers in the striate cortex

Answer 53

cytoarchitecture

Question 54

describe binocular vision (combining inputs from both eyes)

Answer 54

-lat geniculate nucleus receives input from both eyes (monocular) -LGN input remains segregated in layer 4 of the striate cortex (ocular dominance columns) (monocular) -layer 4 send their outputs to other cortical layers (binocular vision)

Question 55

what is involved in complex visual pathways

Answer 55

extrastriate cortex

Question 56

what are the 2 complex visual pathways

Answer 56

dorsal (where) path and ventral (what) path

Question 57

what are each pathway responsible for and where do they project to

Answer 57

dorsal: project to parietal lobe, and responsible of spatial aspect of vision (analysis of motion) ventral: projects to temporal lobe responsible for object recognition

Question 58

consequence of damage at Left lat and med visual field before optic chiasm

Answer 58

Left is gone R is intact

Question 59

consequence of damage at Left med visual field before optic chiasm

Answer 59

R and L lat is intact , L med is gone

Question 60

consequence of damage at L and R visual field at optic chiasm

Answer 60

L med and R med are intact, L lat and R lat are gone

Question 61

consequence of damage at visual field at med optic tract before geniculate nucleus

Answer 61

L lat and R med are intact, R lat and L med are gone

Question 62

consequence of damage at visual field at med optic tract after geniculate nucleus

Answer 62

L lat and R med are intact, R lat and L med are gone