Sense Organs

Multiple Choice Type

(Select the most appropriate option in each case).

Question 1

Which part of the eye is grafted in a needy patient from a donated eye?

1. Conjunctiva
2. Cornea ✓
3. Choroid
4. Ciliary muscles

Question 2

Which part of our ear is shaped like a snail shell?

1. Semi-circular canals
2. Cochlea ✓
3. Stapes
4. Eustachian tube

Question 3

The three parts of human ear contributing in hearing are:-

1. Cochlea, ear ossicles and tympanum ✓
2. Semicircular canals, utriculus and sacculus
3. Eustachian tube, tympanum and utriculus
4. Perilymph, ear ossicles and semicircular canals

Question 4

The region in the eye where the rods and cones are located is the

1. Retina ✓
2. Cornea
3. Choroid
4. Sclera

Very Short Answer Type

Question 1

Name the following:

(a) The photosensitive pigment present in the rods of the retina.

(b) The part which equalizes the air pressure in the middle and external ear.

(c) The ear ossicle attached to the tympanum.

(d) The tube which connects the cavity of the middle ear with the throat.

(e) The part of the eye responsible for its shape.

(f) The nerves which transmit impulse from ear to the brain.

(g) The photoreceptors found in the retina of the eye.

(h) The eye defect caused due to shortening of the eye ball from front to back.

Answer

(a) Rhodopsin

(b) Eustachian tube

(c) Hammer

(d) Eustachian tube

(e) Sclerotic layer or Sclera

(f) Auditory nerves

(g) Rods and cones

(h) Hypermetropia

Question 2

Note the relationship between the first two words and suggest the suitable word/words for the fourth place.

(a) Cones: Iodopsin :: Rods: ________.

(b) Sound: Ear Drum :: Dynamic Balance: __________.

Answer

(a) Cones: Iodopsin :: Rods: rhodopsin

(b) Sound: Ear Drum :: Dynamic Balance: semi-circular canals

Question 3

Which one or more of the expressions in column II are appropriate for the items listed in column I? Match the correct pairs:

Answer

Short Answer Type

Question 1

State whether the following statements are true (T) or false (F). If false, correct them by changing any one single word in each.

(a) Deafness is caused due to rupturing of the pinna.

(b) Semicircular canals are concerned with static (positional) balance.

Answer

(a) False
Corrected statement — Deafness is caused due to rupturing of the eardrum.

(b) False
Corrected statement — Semicircular canals are concerned with dynamic balance.

Question 2

Where are the following located? State their main functions:

(a) Yellow spot

(b) Lacrimal gland

(c) Organ of Corti

(d) Semicircular canal

(e) Oval window

(f) Utriculus

Answer

(a) Yellow spot lies at the back of the eye almost at the centre on the horizontal axis of the eyeball. It is the region of brightest vision and also of colour vision.

(b) Lacrimal glands are located at the upper sideward portion of the eye orbit. They pour the secretion in the form of tears which serves as a lubricant, antiseptic and even washes away dust particles from the eyes.

(c) Organ of Corti is present in the middle cochlear canal of the ear. It helps in hearing.

(d) Semicircular canals are located in the inner ear. These help in maintaining the dynamic equilibrium of the body.

(e) Oval window is located in the middle ear. It helps in setting the fluid in the cochlear canals into vibration.

(f) Utriculus is located in the inner ear. It joins the semi-circular canals to cochlea. It also helps in maintaining static balance of the body.

Question 3

Given below are two sets (a) and (b) of five parts in each. Rewrite them in correct sequence.

(a) Cochlea, tympanum, auditory canal, ear ossicles, oval window

(b) Conjunctiva, retina, cornea, optic nerve, lens.

Answer

(a) Auditory canal, tympanum, ear ossicles, oval window, cochlea

(b) Conjunctiva, cornea, lens, retina, optic nerve.

Question 4

Given below are certain structures. Write against each their specific functional activity.

(a) Cochlea

(b) Auditory nerve

(c) Retina

(d) Choroid

(e) Sacculus

Answer

(a) Cochlea — Cochlea contains organ of Corti which contains sensory cells for hearing. They transmit sound impulses to the brain through auditory nerve.

(b) Auditory nerve — It is the main nerve formed by nerve fibres arising from the sensory cells present in cochlea. This nerve carries sound impulses from inner ear to the brain.

(c) Retina — It is the innermost layer of eye which is sensitive to light. Retina forms the image of an object seen by the eyes.

(d) Choroid — It is middle vascular layer of the eyeball. Choroid provides nourishment to the eye.

(e) Sacculus — It is a part of semicircular canals of the inner ear. It contains sensory cells called macula which help in static balance of the body when it is in stationary position.

Question 5

Complete the following table by filling in the blank spaces.

Answer

Question 6

Name the following:

(a) Two pigments of the sensory cells.

(b) Two types of adaptations.

(c) Two kinds of accommodations.

(d) Three layers of the eyeball.

Answer

(a) Rhodopsin or visual purple and iodopsin or visual violet.

(b) Dark adaptation and light adaptation.

(c) Distant vision accommodation and near vision accommodation.

(d) Sclera, choroid and retina.

Question 7

Name the eye defects caused due to each of the following:

Answer

Descriptive Type

Question 1

Define the following terms:

(a) Conjunctiva

(b) Macula lutea

(c) Adaptation

(d) Ampulla

Answer

(a) Conjunctiva — A thin membrane covering the front part of the eye . It is continuous with the inner lining of the eyelids.

(b) Macula lutea — Macula lutea or yellow spot is a point in the centre of the retina where rods and cones are highly concentrated which offers brightest vision.

(c) Adaptation — Adaptation is the ability to adjust vision in bright and dark areas.

(d) Ampulla — Ampulla is the swollen wide part of each semicircular canal which contains sensory cells called cristae which help in dynamic equilibrium or dynamic balance of the body when it is in motion.

Question 2

Differentiate between members of each of the following pairs with reference to what is asked in brackets.

(a) Myopia and hyperopia (type of lens used for correction)

(b) Rods and cones (sensitivity)

(c) Aqueous humour and vitreous humour (location)

(d) Near and distant accommodation (shape of lens)

(e) Dark and light adaptation (pigments which will be regenerated)

(f) Night blindness and colour blindness (sensory cells which cannot function properly)

Answer

(a) Difference between myopia and hyperopia (type of lens used for correction) —

(b) Difference between rods and cones (sensitivity) —

(c) Difference between aqueous humour and vitreous humour (location) —

(d) Difference between near and distant accommodation (shape of lens) —

(e) Difference between dark and light adaptation (pigments which will be regenerated) —

(f) Difference between night blindness and colour blindness (sensory cells which cannot function properly) —

Question 3

Give reason:

(a) Sometimes medicines dropped into the eyes come into the nose and even throat.

(b) Three small bones of ear ossicles are advantageous as compared to one single bone for hearing.

(c) Blind spot is considered as 'area of no vision'.

Answer

(a) Sometimes medicines dropped into the eyes come into the nose and even throat because tear ducts drain off the liquid into a sac lying at the inner angle of the eye and a nasolacrimal duct conducts the secretion into the nasal cavity.

(b) Three small bones of ear ossicles transmit the vibrations received by the tympanum and amplify them. If these were replaced by a single bone, the vibrations received by the tympanum would not be amplified. Hence, three small bones of ear ossicles are advantageous as compared to one single bone for hearing.

(c) There are no sensory cells in the blind spot and therefore, this is considered as 'area of no vision' and image striking it cannot be perceived.

Question 4

Answer the following:

(a) What is meant by power of accommodation of the eye? Name the muscles of the eye responsible for the same.

(b) Mention the characteristics of the image that falls on the retina of the eye.

Answer

(a) The process of focusing the eye at different distances is called the power of accommodation. The ciliary muscles are responsible for the power of accommodation.

(b) The image formed on the retina is inverted and real.

Question 5

Describe the mechanism of focusing the image of a distant object in your eye when you raise your head after reading a book.

Answer

Light rays from the object enter the eyes through the transparent structures.
For distant vision, the lens is more flattened or thinner.
For near vision, the lens becomes more convex or rounded.
While reading a book, the lens is more convex or rounded due to contraction of ciliary muscles because the book is usually read from a short distance. When we raise our head and look at a distant object, the ciliary muscles relax to build the tension on the suspensory ligament so that they can stretch the lens. This change in the curvature of the lens makes us focus on distant object.

Question 6

By closing the eyes and gently pressing them with your palms, you may see some specs of brilliant light. How do you get this sensation while there is no light entering your eyes?

Answer

The sensation of light persists for a period of time after we look at a bright object and then close eyes. It lasts for one-tenth of a second. Due to this by closing the eyes and gently pressing them with our palms, we see some specs of brilliant light.

Question 7

Name the three ear ossicles. How do they contribute in the mechanism of hearing?

Answer

The three ear ossicles are: Malleus (hammer), Incus (anvil) and Stapes (stirr up).
The last ear ossicle, stapes, vibrates and transmits the vibration to the oval window.
The role of other two ear ossicles is to magnify the vibration of stapes as a result of their lever like action.

Structured / Application / Skill Type

Question 1

With reference to the functioning of the eye, answer the questions that follow:

(a) What is the shape of the lens during (1) near vision (2) distant vision?

(b) Name the two structures in the eye responsible for bringing about the change in the shape of the lens.

(c) Name the cells of the retina and their respective pigments which get activated (1) in the dark and (2) in the light.

Answer

(a) The shape of the lens during (1) near vision is more convex or rounded (2) distant vision is more flattened or thinner.

(b) Ciliary muscles and suspensory ligament

(c) In the dark:
     Cells — rod cells
     Pigment — rhodopsin

     In the light:
     Cells — cone cells
     Pigment — iodopsin

Question 2

With reference to the human ear, answer the questions that follow:

(a) Give the technical term for the structure found in the inner ear.

(b) Name the part of the ear associated with (1) static balance (2) hearing (3) dynamic balance.

(c) Name the nerve, which transmits messages from the ear to the brain.

Answer

(a) Membranous labyrinth

(b) The part of the ear associated with:

1. Static balance — Utriculus and sacculus (vestibule)
2. Hearing — Cochlea
3. Dynamic balance — Semi-circular canals

(c) Auditory nerve transmits messages from the ear to the brain.

Question 3

The figure given below refers to the vertical section of the eye of a mammal. Study the figure carefully and answer the following questions.

(a) Label the guidelines shown as 1 to 10.

(b) Write one important role of parts shown as 3 and 7.

(c) Write one structural difference between the parts shown as 9 and 10.

(d) Mention one functional difference between the parts shown as 6 and 8.

Answer

(a) The guidelines are labelled below:

• 1 → Aqueous chamber
• 2 → Lens
• 3 → Iris
• 4 → Cornea
• 5 → Conjunctiva
• 6 → Sclera
• 7 → Choroid
• 8 → Retina
• 9 → Yellow spot
• 10 → Optic nerve (Blind spot)

(b) Part 3 (Iris) — It contains radial muscles to dilate the pupil and circular muscles to constrict the pupil.

Part 7 (Choroid) — It is the middle layer of the eyeball, richly supplied with blood vessels and provides nourishment to the eye.

(c) Part 9 (yellow spot) contains sensory cells especially the cone cells while part 10 (blind sport) contains no sensory cells.

(d) Part 6 (sclera) gives shape to the eyeball and part 8 (retina) acts as screen to form image of an object.

Question 4

Given below is a diagram depicting a defect of the human eye? Study the same and answer the questions that follow:

(a) Name the defect shown in the diagram.

(b) Give two possible reasons for this defect.

(c) Name the parts labelled 1 to 4.

(d) Name the type of lens used to correct this eye defect.

(e) Draw a labelled diagram to show how the above mentioned defect is rectified using the lens named above.

Answer

(a) Myopia

(b) The two possible reasons for myopia are either the eye ball is lengthened from front to back or the lens is too curved.

(c) Parts labelled 1 to 4 are:

• 1 → vitreous humour
• 2 → blind spot
• 3 → lens
• 4 → pupil

(d) Concave lens

(e) The below diagrams show the condition of Myopia and how it is corrected using a Concave Lens:

Question 5

The figure below is the sectional view of a part of the skull showing a sense organ:

(i) Name the sense organ.

(ii) What are the parts labelled 'm', 'i' and 's'? What do these parts constitute collectively?

(iii) What do you call the part shown in the form of a spiral? What is its function?

(iv) Name the part labelled 'tm'. What is its function?

Answer

(i) Ear

(ii) The parts are:

• m → malleus
• i → incus
• s → stapes

These are collectively called as ear ossicles.

(iii) Cochlea.
The vibrating movements in the hair of the sense cells of cochlea transmit the impulse for hearing to the brain via auditory nerve.

(iv) Tympanic membrane.
It vibrates and then sets the ear ossicles into vibration in the process of hearing.

Question 6

Given below is a diagram of a part of the human ear. Study the same and answer the questions that follow:

(i) Give the collective biological term for Malleus, Incus and Stapes.

(ii) Name the parts labelled A, B and C in the diagram.

(iii) State the functions of the parts labelled 'A' and 'B'.

(iv) Name the audio receptor region present in the part labelled 'A'.

Answer

(i) Ear ossicles

(ii) The labelled parts are:

• A → Cochlea
• B → Semicircular canals
• C → Ear ossicles

(iii) Cochlea helps in transmitting impulses to the brain via the auditory nerve. Semicircular canals help in maintaining dynamic equilibrium of the body.

(iv) Organ of Corti

Question 7

Draw a labelled diagram of the inner ear. Name the part of the inner ear that is responsible for static balance in human beings.

Answer

Below is the labelled diagram of the inner ear:

Utriculus and Sacculus collectively termed as vestibule are responsible for maintaining static balance in human beings.

Question 8

Have a look at the posture of this girl who is reading a book and answer the questions which follow:

(a) Name the problem she is facing.

(b) What are the two conditions shown in sections A and B of the eye as applicable to her?

(c) What kind of reading glasses does she need ?

Answer

(a) Myopia

(b) The condition shown in section A is Hyperopia as the image is formed behind the retina. The condition shown in section B is Myopia as the image is formed in front of the retina.

(c) She needs reading glasses with concave lens.

Question 9

The figure given below shows the principal parts of a human ear. Study the diagram and answer the following questions.

(a) Label the parts 1 to 8.

(b) State the role of parts 6, 7 and 8.

(c) Why is it harmful to use a sharp object to remove ear wax? Mention the number and name of the part involved.

Answer

(a) The labelled parts are:

• 1 → External ear (pinna)
• 2 → Ear drum (tympanum)
• 3 → Auditory canal
• 4 → Malleus
• 5 → Semicircular canals
• 6 → Cochlea
• 7 → Auditory nerve
• 8 → Eustachian tube

(b) Part 6 (Cochlea) — It contains sensory cells for hearing.

Part 7 (Auditory nerve) — It transmits impulse of hearing to the brain.

Part 8 (Eustachian tube) — It equalizes air pressure on both the sides of the tympanum.

(c) It is harmful to use a sharp object to remove ear wax as it can rupture the ear drum.
The part involved is part 2 — Ear drum (tympanum).