14.2

Question 1

sense organ

Answer 1

groups of receptor cells, responding to a specific stimuli, such as light, sound, touch, temperature and chemical.

Question 2

eye structure

Answer 2

1- cornea
2- iris
3- pupil
4- lens
5- retina
6- blind spot
7- optic nerve

Question 3

characteristics of cornea

Answer 3

transparent - no blood vessels, curved.

Question 4

function of cornea

Answer 4

refracts and focuses light.

Question 5

characteristics of iris

Answer 5

colored part.

Question 6

function of iris

Answer 6

controls how much light enters the pupil.

Question 7

function of pupil

Answer 7

opening through which light enters.

Question 8

function of lens

Answer 8

refracts and focuses light onto the retina.

Question 9

function of retina

Answer 9

contains photoreceptors, light receptors detect light, cones - sensitive to bright light, rods - sensitive to dim light, no blood vessels.

Question 10

characteristics of fovea

Answer 10

a point where the image is the clearest, most detailed colored image
it contains only cones.

Question 11

characteristics of sclera

Answer 11

the white part of the eye.

Question 12

characteristics of choroid

Answer 12

contains blood vessels.

Question 13

characteristics of blind spot

Answer 13

a point where no image is formed, no receptors, no cones or rods.

Question 14

function of optic nerve

Answer 14

carries electrical impulses to the brain.

Question 15

explain the pupil reflex

Answer 15

light is the stimulus, photoreceptor cells detect light, electrical impulses are transmitted through the optic nerve to the brain, to relay, then to motor neuron, to the effector muscles, iris circular muscle and radial muscle.

Question 16

in bright light:

Answer 16

less light enters the eye, circular muscles contract, radial muscles relax, pupil constricts.

Question 17

in dim light:

Answer 17

more light enters the eye, circular muscles relax, radial muscle contracts, pupil dilates.

Question 18

characteristics of rods

Answer 18

sensitive to dim light, found in large numbers in the retina, gives image in black or white, sends electrical impulses to brain at night, each 2 or 3 are connected to the brain by 1 nerve cell.

Question 19

characteristics of cones

Answer 19

sensitive to bright light, found in fovea, each is connected to the brain by 1 nerve cell, 3 kinds or cones absorbing light at different colors: red, green, blue.

Question 20

describe the distribution of cones and rods

Answer 20

found in the retina, most concentration of cones in the fovea, each cone is connected to one nerve cell, 3 types of cones, each 2 or 3 rods are connected by one nerve cell, no rods or cones in the blind spot, more rods than cones.

Question 21

describe how cones and rods function

Answer 21

rods detects dim light, cones detect bright light, rods stimulates night vision, cones stimulate colored vision, rods give black and white images, cones give colorful images, electrical impulses are transmitted from rods and cones through the optic nerve to the brain.

Question 22

accommodation

Answer 22

changing the distance between the object and the eye lens

Question 23

refraction

Answer 23

cornea and lens bend the light rays

Question 24

describe how an image is formed in the retina

Answer 24

light is reflected on the eye
refraction happens
because of refraction, the image is formed inverted - upside down

Question 25

near object

Answer 25

ciliary muscles contracts suspensory ligaments become loose, slacken lens become shorter, thicker, more curved, more convex pupil constricts light rays diverging greatly light is focused on retina thick lens

Question 26

far object

Answer 26

ciliary muscles relax suspensory ligaments tighten lens is pulled longer, thicker, less curved, less convex pupil becomes wider light rays diverging slightly light is focused on retina thin lens