Chapter 12: the eye

Question 1

sense organs

Answer 1

carry messages about the external/ internal environment to the CNS

Question 2

a stimulus is a source of energy…

Answer 2

converted from one form to another

Question 3

sensory receptors

Answer 3

modified ends of sensory neurons that are activated by specific stimuli 
sensory receptors (pick up stimulus) --> sensation & perception @ brain

Question 4

sensory adaptation & example

Answer 4

occurs when you have adjusted to a change in environment

eg wearing clothes

Question 5

photo-receptors

Answer 5

eyes (rods & cones)

Question 6

chemoreceptors

Answer 6

tounge (taste buds), nose (olfactory cells), carotid arteries & brain (blood pH)

Question 7

mechanoreceptors

Answer 7

ear (inner ear stereocilia for balance, sound), proprioreceptors and touch (skin)

Question 8

thermoreceptors

Answer 8

skin (heat & cold receptors)

Question 9

iris

Answer 9

colored muscle regulation the amount of light entering eye

opening for light to go in = pupil

Question 10

3 separate layers of the eye

Answer 10

sclera, choroid layer, retina

Question 11

sclera

Answer 11

outermost layer (protective) covered by a cornea

• no blood vessels; gets O2 from dissolved tears & nutrients from the aqueous humor
• lack of O2 and nutrients = glaucoma

Question 12

cornea

Answer 12

transparent tissue that refracts light toward pupil

covers sclera

Question 13

3 parts of choroid layer

Answer 13

iris, lens, viterous humor

Question 14

choroid layer

Answer 14

middle layer of eye that has pigments that prevent scattering by absorbing stray light

Question 15

lens

Answer 15

focuses image on the retina by action of dorsal & ventral ciliary muscles

Question 16

vitreous humor

Answer 16

cloudy, jelly-like material maintains eye shape and lets light through

Question 17

retina

Answer 17

inner most layer
composed of 3 layer of cells:
1. light sensitive cells: rods & cones
2. bipolar cells: pass message from rods& cones to cells of optic nerve
3. optic nerve cells: ganglion cells

Question 18

light conversion occurs at ____

Answer 18

the RETINA layer

Question 19

rods vs cones

Answer 19

rods: used to view dim light
cones: used to identify color (red, blue, & green cones)

Question 20

fovea centralis

which layer?

Answer 20

• closely packed with rods and cones @ center of the RETINA; most sensitive area of the eye

Question 21

optic disk

Answer 21

ie blind spot

lack of rods & cones: where the optic nerve comes into contact with retina

Question 22

accomodation

Answer 22

adjustments made to the lens & pupil to view near or far objects

Question 23

Accommodation - focusing for close vision

Answer 23

• thickening lens shape by flexing ciliary muscles, allowing tendons to relax
• pupil constricts
• increased refraction

Question 24

accommodation- focusing for distant vision

Answer 24

• lens becomes thin (muscles relax, tendons pull)
• pupil may also dilate to allow as much light as possible
• decreased refraction

Question 25

cataracts

Answer 25

lens or cornea becomes clouded

Question 26

astigmatism

Answer 26

abnormal curvature of cornea or surface of the lens

Question 27

myopia

Answer 27

nearsightedness

- image is focused in front of the retina

Question 28

hyperopia

Answer 28

farsightedness

image is focused beyond the retina (eyeball too small)

Question 29

colorblindness

Answer 29

inherited condition; lacking certain cones (red, blue, or green)

Question 30

afterimages

Answer 30

can be (+) - ex strobe light
or (-) ex red/ green cones
- caused by fatigue of a cone in an area of the retina

Question 31

sequence of passage of energy (through eye, conversion, where it gets interpreted in brain)

Answer 31

cornea –> aqueous humor–> pupil –> lens–> vitreous humor–> passes the cells in retina layer –> strikes choroid layer (absorbs light & reflects energy to..) –> receptor cells of the retina: rods & cones (covert light to chemical energy) –> chemical signal leaves eye through optic nerve –> occipital lobe of cerebrum interprets vision

Question 32

extrinsic muscles

Answer 32

allow your eye to turn

- conscious control (frontal lobe)

Question 33

receptor cells of the retina

Answer 33

rods and cones

Question 34

optic nerve cells

Answer 34

ganglion cells (in retina)