13. Vision

Question 1

scotopic vision

Answer 1

monochromatic vision produced through the rods in the low light

Question 2

photopic vision

Answer 2

chromatic vision produced through the cones under well-lit conditions

Question 3

dark current

Answer 3

contionous inflow of Na+ and Ca++ into rods and cones in dark through cGMP-regulated channels, causing hypopolarization and glutamate release

Question 4

hemidecussation

Answer 4

partial crossing of optic fibers in the chiasma opticum ensuring that information collected from the same part of the visual field by the two retinas is analyzed in the same hemisphere

Question 5

optical illusion

Answer 5

distortion of visual perception at the cortical level caused by previous experiences

Question 6

sclera

Answer 6

the outermost, white layer of the eyeball

Question 7

cornea

Answer 7

frontal, transparent part of the sclera with the highest refracting power

Question 8

conjunctiva

Answer 8

very sensitive epithelial membrane covering the sclera and cornea and lining the inside of the eyelids

Question 9

iris

Answer 9

circular, pigmented membrane behind the cornea, perforated by the pupil; its contraction regulates the amount of light passing into the eye

Question 10

choroid

Answer 10

the middle, vascularized layer of the eyeball, including the iris and the ciliary body (ciliary muscles)

Question 11

fovea centralis

Answer 11

a depression in the center of the macula of the retina, the area of the most acute vision, where only cones are present

Question 12

blind spot (optic disc)

Answer 12

the spot on the retina, where the axons of the ganglion cells and blood vessels penetrate the wall of the eyeball; no receptor cells are found here

Question 13

muscular ciliaris

Answer 13

the lens is attached to the ciliary body (ciliary muscles) in the eye, its contraction is needed for accomodation

Question 14

glaucoma

Answer 14

eye disease caused by the excessive intraocular pressure due to a disturbance in the production and reabsorption of the aqueous humor

Question 15

cataract

Answer 15

eye disease caused by an opacity of the lens

Question 16

presbiopia

Answer 16

in elderly people the lens looses its flexibility, thus accomodation is no longer possible for short distances; corrected by reading glasses

Question 17

cis-retinal

Answer 17

organic compound derived from vitamin A; in visual pigments it absorbs the energy of photons

Question 18

transducin

Answer 18

G-protein in rods and cones, activated by the photopigment during light detection

Question 19

rhodopsin

Answer 19

photopigment of the rods

Question 20

opsin

Answer 20

protein part of the photopigment

Question 21

horizontal cell

Answer 21

inhibitory interneuron in the retina connecting receptor cells

Question 22

amacrin cell

Answer 22

interneuron in the retina establishing horizontal connections mostly close to the ganglion cells

Question 23

melanopsin

Answer 23

photopigment contained by the W ganglion cells

Question 24

M ganglion cell

Answer 24

ganglion cell projecting the magnocellular layer of the corpus geniculatum laterale

Corpus = body

Question 25

P ganglion cell

Answer 25

ganglion cell projecting the parvocellular layer of the corpus geniculatum laterale Corpus = body

Question 26

color blindness

Answer 26

disturbance of the color vision caused in most cases by a mutation in the genes coding for the photopigments; the most common form is the red/green color blindness