Sense Organs

Question 1

Name the five types of receptors

Answer 1

1. mechanoreceptors - touch
2. Chemoreceptors - tongue, nose
3. Photoreceptors - rods cones
4. Thermoreceptors - skin
5. Phono receptors - sound

Question 2

How many muscles help in moving of eye?

Answer 2

Six muscles

Question 3

What are the 6 parts of eyes?

Answer 3

1. Orbits or sockets
2. Eyelids
3. Eyebrows
4. Tear glands (lacrimal glands)
5. Tear ducts
6. Conjunctiva

Question 4

State functions of tears

Answer 4

1. Emotions
2. Help in killing germs with lysozyme
3. Wash away dust
4. Lubricate surface of eye

Question 5

What are the three layers of eyes?

Answer 5

1. Sclera or sclerotic layer
2. Middle choroid
3. Inner retina

Question 6

What is the dark black pigment in chorus layer?

Answer 6

Melanin. It prevents light rays from reflecting and scattering inside eye

Question 7

What are the two types of sense cells present in retina?

Answer 7

Rods and cones

Question 8

What do rod cells contain? What do cones contain?

Answer 8

Rods - rhodopsin or visual purple
Cones - iodopsin or visual violet

Question 9

What is the other name of yellow spot?

Answer 9

Macula lutea. This contains maximum number of senosry cells. This is the region of brightest vision.

Question 10

What is the blind spot?

Answer 10

The blind spot has no sensory cells. No point of vision.

Question 11

What is the lens?

Answer 11

The lens is a transparent, flexible, biconvex ,crystalline body located just behind the pupil. It contains transparent lens fibers.

Question 12

What are the two chambers of eye?

Answer 12

1. Aqueous chamber - contains aqueous humour. Aqueous humour keeps lens moist, refracts light and protects against physical shock.
2. Vitreous humour - contains vitreous humour. It helps in keeping shape of eyeball, protects retina and nerve endings

Question 13

Name the common defects of the eye:

Answer 13

1. Near or short sightedness (myopia)
   Reasons: eye hall is lengthened from front to back or lens is too curved
   Correction: concave lens
2. Far or long (hyperopia)
   Reasons: shortening of eyeball or lens is too flat.
   Correction: convex lens
3. Astigmatism - is a defect in which some parts of object are seen in focus while others are blurred. Arises due to uneven curvature of cornea. Corrected by cylindrical lenses.
4. Presbyopia - condition affecting older ppl who cannon see near objects. Corrected by convex lens.
5. Cataract - lens turns opaque. Corrected by surgically removing lense.
6. Night blindness - due to non formation of visual purple of rods. Deficiency of Vitamin A.
7. Colour blindness- cannot discriminate between red and green. Mostly occurs in males.
8. Corneal opacities
9. Squint : cross eye and wide eye. Surgery and exercise

Question 14

What are two functions of ear?

Answer 14

1. Hearing
2. Body balance

Question 15

State three divisions of ear:

Answer 15

1. Outer ear- pinna, auditory canal, ear drum (tympanum)
2. Middle ear - tiny bones : malleus(hammer), incus (anvil), stapes (stirrup), Eustachian tube.
3. Inner ear of membranous labyrinth-
   Cochlea, semicircular canals, vestibule.

Question 16

What is the cochlear canal filled with?
What is the main organ of hearing?

Answer 16

Endolymph and perilymph
Organ of corti.

Question 17

What is the collective name for the bones in ear?

Answer 17

Ear ossicles

Question 18

What is the collective name utriculus and sacculus ?

Answer 18

Vestibule. These parts contain sensory cells for static balance.

Question 19

What is concerned with dynamic equilibrium?

Answer 19

The sensory cells in semicircular canals.