vision

Question 1

what is the definition of “seeing”?

Answer 1

formation by cornea and lens of a real, reduced, up-side-down image on the back of the eye. Transmission of visual information to the visual cortex.

Question 2

what does the lacrimal gland do?

Answer 2

secretes tears

Question 3

what does the orbit do?

Answer 3

bony cavity that protects the eye

Question 4

what doe sthe nasolacrimal duct do?

Answer 4

drains tears into nasal cavity

Question 5

what are the substructures of the retina?

Answer 5

ganglion
amacrine
bipolar
horizontal
rods/cones
(cells)

Question 6

rays must pass through…?

Answer 6

Cornea
Anterior chamber
Pupil
Lens
Vitreous
Inner retinal layers
Reaches photoreceptors

Question 7

visual based neural signals pass through…?

Answer 7

Photoreceptors
Intermediate retinal neurons
Retinal ganglion cells (optic nerve)
LGN
To visual cortex

Question 8

where are the blood vessels of the eye located?

Answer 8

choroid layer

Question 9

whataxons become the optic nerve?

Answer 9

retinal ganglion cell axons

Question 10

what is the focus point of the eye called?

Answer 10

fovea

Question 11

what is the accomidation reflex used for?

Answer 11

near objects

Question 12

what is the accomidation reflex?

Answer 12

A physiological reflex that permits focusing on near and far objects by changing the curvature of the lens

Question 13

what woulf happen without accomidation?

Answer 13

ays would focus behind fovea

Question 14

what happens to the eye structures during the accomidation reflex for far away objects?

Answer 14

relaxation of ciliary body muscles; tightens zonule ligaments, stretches lens. Sympathetically controlled. Decreases power.

Question 15

what happens to the eye structures during the accomidation reflex for close objects?

Answer 15

contraction of ciliary body muscles; moves ciliary body inward, loosens zonule ligaments, lens gets fatter (more convex). Parasympathetically controlled. Increases power

Question 16

what shape is the ciliary body?

Answer 16

DONUT!!!

Question 17

what is the neural pathway for mediating accomidation

Answer 17

optic nerves - oculomotor nuclei - oculomotor nerves - ciliary body muscles

Question 18

what is an emmetropic eye?

Answer 18

a normal eye

Question 19

what happens to the eye during low light so you can see?

Answer 19

iris dilator pupillae muscles contract, radial fibers shorten, pupil diameter increases, allows more rays in

Question 20

what happens to the eye during high light?

Answer 20

iris constrictor pupillae muscles contract, concentric fibers shorten, pupil diameter decreases, blocks some rays

Question 21

what is the neural pathway for mediating pupillary reflex?

Answer 21

optic nerves - oculomotor nuclei - oculomotor nerves - iris muscles
Visual acuity:

Question 22

what is visual acuity?

Answer 22

Ability of the eye to see fine detail

Question 23

waht affects visual acuity?

Answer 23

eyeball shape, pupil size, illumination, exposure time, area stimulated, movement

Question 24

what is the snellen visual acuity test?

Answer 24

ability to resolve a spatial pattern separated by a visual angle of one minute of arc at 20 feet

Question 25

what does the bottom number of the snellen test mean?

Answer 25

distance that the normal eye can see the same letters on the chart

Question 26

what do photoreceptors do?

Answer 26

transform light intensity and color into chemical and electrical signals to trigger activity of retinal cells

Question 27

what is the eyes blind spot?

Answer 27

optic disc

Question 28

what are the characteristics of cone photorecpetors?

Answer 28

color specific and high acuity. Concentrated in the fovea

Question 29

what arae the 3 types of cone receptors, their size and colours?

Answer 29

S - short - blue M - middle - green L - long - red

Question 30

what are the characteristics of rod photoreceptors?

Answer 30

no color specificity, low acuity, high sensitivity. Present in the peripheral retina. Low light vision

Question 31

where are the photoreceptors situated?

Answer 31

back of rrtina

Question 32

what is the function of photoreceptors?

Answer 32

convert photoni energy to chemical signals

Question 33

how do photoreceptors get renewed?

Answer 33

Discs of visual pigment are constantly renewed New discs added to base of outer segment Old discs displaced at the top and engulfed by retinal pigment epithelium on a diurnal cycle

Question 34

what happens in a photoreceptor cascade in the dark?

Answer 34

rhodopsin is unstimulated. cGMP is available. cGMP binds to cation channels and are kept open by cGMP to depolarize the photoreceptors.

Question 35

what happens in a photoreceptor cascade in the light?

Answer 35

rhodopsin is stimulated, starting a cascade involving transducin and phosphodiesterase. The cascade becomes more activated and leads to phosphodiesterase degrading cGMP. cGMP levels begin to decrease, cation channels begin to close and start to hyperpolarize the photoreceptor.

Question 36

what stimulates the transmission of impulses to the visual cortex?

Answer 36

hyperpolarization of photoreceptors

Question 37

do rod-ganglion cells show high or low convergence?

Answer 37

high

Question 38

do cone-ganglion cells show high or low convergence?

Answer 38

low

Question 39

how to horizontal cells connect photoreceptors?

Answer 39

laterally

Question 40

what do on and off centers of ganglion cells do?

Answer 40

offer opposite responses determined by the sensitivity of the cone receptive fields they serve.

Question 41

where does light stimulus go on the way down the visual pathway on the temporal side?

Answer 41

stays temporal

Question 42

where does light go on the way down the visual pathway on the nasal side?

Answer 42

crosses at optic chiasm

Question 43

what does cranial nerve III do?

Answer 43

controls pupillary constriction