Sense Organs

Question 1

define receptors

Answer 1

any specialised tissue or cell sensitive to a specific stimulus

Question 2

orbits

Answer 2

eyes are located in these deep sockets
on the front side of the head

Question 3

tear glands

Answer 3

at the upper sideward portion of orbit
6 to 12 glands present

Question 4

function of lacrimal gland

Answer 4

1. blinking spreads the liquid which acts as lubricant
2. washing away dust
3. antiseptic due to lysozyme which kills germs
4. tears communicate emotions

Question 5

conjuctiva

Answer 5

thin membrane covering front part of the eye
continuous with the inner lining of eyelids

Question 6

layers of wall of eyeball

Answer 6

1. outer sclerotic
2. middle choroid
3. inner retina

Question 7

sclerotic layer

Answer 7

tough fibrous tissues
white in colour
bulges out and becomes transparent in front, where it covers the coloured part of eye, called cornea

Question 8

choroid layer

Answer 8

blood vessels for nourishment
contains melanin which prevents light rays from reflecting and scattering inside eye
in front, choroid expands to form ciliary body

Question 9

iris

Answer 9

extension of choroid

Question 10

function of radial muscles in iris

Answer 10

widen the pupil- adjust amount of light entering

Question 11

function of circular muscle

Answer 11

constrict the pupil

Question 12

rod cells in retina

Answer 12

sensitive to dim light
do not respond to colour
contain rhodopsin/ visual purple
throughout retina

Question 13

cones in retina

Answer 13

sensitive to bright light
responsible for colour vision
iodopsin/ visual violet
only in yellow spot

Question 14

yellow spot

Answer 14

AKA macula lutea
at the BACK OF THE EYE, CENTRE ON THE HORIZONTAL AXIS OF EYEBALL
has maximum sensory cells
region of brightest vision

Question 15

blind spot

Answer 15

LATERAL TO YELLOW SPOT ON NASAL SIDE
no sensory cells
all sensory cells’ nerve fibres converge and bundle together here to leave as optic nerve

Question 16

lens

Answer 16

transparent, flexible, biconvex
just behind the pupil
contains lens fibres transparent

Question 17

suspensory ligaments

Answer 17

lens is held in position by these fibres, and are attached to ciliary body

Question 18

ciliary body

Answer 18

at junction of choroid and iris
contains muscles which on contraction/relaxation, change shape of lens for viewing different distances

Question 19

chambers of eye

Answer 19

1. aqueous
2. vitreous

Question 20

aqueous humour

Answer 20

between lens and cornea

1. keeps lens moist
2. protects from shock
3. refracts light

aqueous humour is clear watery liquid

Question 21

vitreous chamber (humour)

Answer 21

behind the lens

1. helps in keeping shape of eyeball
2. protects retina and its ending

vitreous humour is jelly-like thicker fluid

Question 22

define accomodation

Answer 22

the process of focusing the eye to see objects at different distances, brought about by making a change in the curvature of elastic lens (by ciliary muscles)

Question 23

dark adaptation due to

Answer 23

1. regeneration of rhodopsin, which was earlier broken down due to light
2. dilation of pupil

Question 24

light adaptation due to

Answer 24

1.visual purple of rods is bleached
2. pupil constricts

Question 25

myopia caused due to

Answer 25

1. eyeball is lengthened from front to back 2. lens is too curved corrected by concave lens

Question 26

hypermetropia due to

Answer 26

1. shortening of eyeball from front to back 2. lens is too flat

Question 27

astigmatism

Answer 27

when some objects are seen in focus while others are blurred 1. uneven curvature of cornea corrected by cylindrical lenses

Question 28

presbyopia

Answer 28

lens loses flexibility cannot see near objects clearly convex lens

Question 29

cataract

Answer 29

1. lens turns opaque, vision is cut down to blindness use highly convex lens, remove lens, small plastic lens behind or front of the iris

Question 30

night blindness

Answer 30

1. non formation of rhodopsin 2. deficiency of vit A which is required for synthesis of pigment

Question 31

colour blindness

Answer 31

1. due to genetic defect rare in females

Question 32

corneal opacities

Answer 32

1. cornea gets scarred and turns opaque/white can cause irritation or vision problems or blindness defective cornea is replaced with healthy cornea

Question 33

squint

Answer 33

two eyes converge- cross eye two eyes diverge- wide eye may cause double vision/ diplopia fixed by surgery and exercise

Question 34

functions of ear

Answer 34

1. hearing 2. body balance

Question 35

divisions of ear

Answer 35

1. outer 2. middle 3. inner

Question 36

outer ear

Answer 36

1. projecting part called pinna/ auricle 2. auditory canal leading to ear drum/tympanum

Question 37

middle ear

Answer 37

1. malleus, incus, stapes 2. eustachian tube connects cavity of middle ear to throat

Question 38

oval window and round window

Answer 38

oval- membrane covered opening leading to inner ear round- membrane covered, connects middle and inner ear

Question 39

inner ear

Answer 39

AKA membranous labyrinth 1. cochlea 2. semicircular canals 3. vestibule

Question 40

cochlea

Answer 40

spiral shapes, looks like snail shell has two and a half turns inner winding is divided into 3 parallel canals middle canal has areas possessing sensory cells sensory cells lie on basilar membrane

Question 41

organ of Corti

Answer 41

lie in the middle canal of the cochlea possess sensory cells spiral organ

Question 42

semicircular canals

Answer 42

set of 3 arranged at right angles to each other in three different planes (one horizontal, two vertical)

Question 43

ampulla

Answer 43

one end of each semicircular canal is widened to form ampulla contains sensory cells for dynamic balance while body is moving

Question 44

vestibule

Answer 44

short stem joining the bases of semicircular canals to the cochlea have UTRICULUS and SACCULUS contain sensory cells for static balance when body is not moving

Question 45

function of eustachian tube

Answer 45

equalises air pressure on either side of ear drum, allowing it to vibrate freely

Question 46

why is vibration of stapes amplified

Answer 46

due to lever like action of the first two ossicles