Class 10 Biology Chapter 3 Important Questions Kerala Syllabus Behind Sensations

A thorough understanding of Class 10 Biology Notes Kerala Syllabus Chapter 3 Important Questions Behind Sensations can improve academic performance.

SSLC Biology Chapter 3 Important Questions Behind Sensations

Behind Sensations Class 10 Important Questions

Question 1.
Select the correct answer.
Statement 1: Stimuli are the circumstances that lead to responses in living beings.
Statement 2: Stimuli can be divided into external stimuli and internal stimuli.
(A) Statement 1 and statement 2 are correct
(B) Statement 1 and statement 2 are wrong
(C) Statement 1 wrong statement 2 correct
(D) Statement 1 correct statement 2 wrong
Answer:
(A) Statement 1 and statement 2 are correct

Question 2.
Find the odd one. Write the common features of others.
Takes food when hungry, A rabbit, upon seeing a lion, gets scared and runs away, Blanketing to keep out cold, Body temperature increases during certain diseases
Answer:
Blanketing to keep out cold, others are situations on internal stimuli.

Question 3.
Complete the statement.
Stimuli are recognised by the body through specialised cells or nerve endings. They are known as …………………
Answer:
Sensory Receptors

Question 4.
Find the odd one and write the peculiarities of others.
Iris, malleus, lens, retina
Answer:
malleus, others are the parts of eyes

Question 5.
Find the relation and fill in the blanks
a) Rod cells: Rhodopsin
Cone cells: ……………
b) Glaucoma: Laser surgery
Cataract: ………………….
Answer:
a) Rod cells: Rhodopsin
Cone cells: Photopsin
b) Glaucoma: Laser surgery
Cataract: Replacing the lens through surgery

Question 6.
Slightly projected transparent anterior part of the sclera?
Answer:
Cornea.

Question 7.
The transparent membrane which protects the sclera, except the cornea?
Answer:
Conjunctiva.

Question 8.
The middle layer of eye, ……………………… which contains a large number of blood vessels.
Answer:
Choroid.

Question 9.
The dark coloured anterior part of choroid is ……………………, which contains the pigment melanin.
Answer:
Iris.

Question 10.
The aperture at the centre of iris?
Answer:
Pupil.

Question 11.
The antagonistic muscles in the iris that regulate the size of eye pupil?
Answer:
Radial muscles (pupillary dilator) and Circular muscles (pupillary constrictor).

Question 12.
Vitamin A helps us for better vision. Give reason.
Answer:
Retinal, the visual pigment found in the photo receptors, is formed from vitamin A.

Question 13.
The bird, owl has no vision in daytime. Why?
Answer:
Owl’s retina is devoid of cone cells and hence no vision in daytime.

Question 14.
Analyse the statement that animals like cat and owl have more vision at night.
Answer:
Cat and owl have more rod cells in their retina, so that they have more vision at night.

Question 15.
Though images of object are formed in both eyes, we can see only one object. Give reason.
Answer:
Cerebrum coordinates the two images and hence get a three-dimensional view of the object.

Question 16.
Find out the odd one. Write down the common feature of others.
Cornea, Cochlea, Choroid, Sclera. (Model 2016)
Answer:
Cochlea. Others are part of eye.

Question 17.
Name the process represented in following illustration? Write the peculiarity of image formed in labelled sense organ? (March 2015)

Answer:
Formation of image in the brain. Peculiarity of the image formed: Real, small.

Question 19.
Find out ‘word pair relation’ and fill in the blanks.
Dim light : Rod cells
Bright light : …………………..
Answer:
Cone cells

Question 20.
Analyse the word pair relationship and fill up the blanks.
Photopsin : Colourblindness
………………… : Night blindness (Model 2013)
Answer:
Rhodopsin

Question 21.
Find the odd one and write the peculiarities of others.
Utricle, sacule, vestibular nerve, cochlea
Answer:
cochlea: others are related to body balancing

Question 22.
Find the relation and fill in the blanks
Cochlea : Auditory nerve
Vestibule : …………………….
Answer:
Cochlea : Auditory nerve
Vestibule : Vestibular nerve

Question 23.
Why certain person feel ear pain as they goes higher altitudes?
Answer:
When we goes higher altitudes, the atmospheric pressure decreases and causes variation in pressure inside the middle ear, which will lead to the pain of ear drum.

Question 24.
Identify the odd one. Write the common feature of the others.
a) Cold, temperature. Pressure, Taste
b) Tympanum, Oval window, Cochlea, Papilla
Answer:
a)

• Taste
• Others senses through skin

b)

• Papilla
• Others are parts of the ear

Question 25.
Write down the names of receptors for recognizing smell and taste.
Answer:
Olfactory receptors (smell)
Taste buds/Taste receptors (taste)

Question 26.
Identify the word pair relationship and fill the missing word. Mention the relation among the pairs.
Euglena : Stigma :: Insects : ……………………..
Answer:
Ommatidia, Sensory diversity in organisms

Question 27.
Arrange the following statements suitably in the table given below.
(a) Receptors in skin.
(b) Receptors help in vision.
(c) Receptors help in taste.
(d) Receptors internal organs.

Help to detect general senses	Help to recognise specific senses

Answer:

Help to detect general senses	Help to recognise specific senses
(a), (d)	(b), (c)

Question 28.
Analyse the illustration of image formation in retina and make a flowchart.

Answer:
Light rays from the object → cornea → Aqueous humor/pupil → lens → vitreous humor → image on retina

Question 29.
The sight of one of the eyes of a participant in the hurdles competition, has lost. Is the participant is apt for participating hurdles competition? Justify your answer.
Answer:
Since the participant lost one of his eyes’ sight, he has no binocular vision and he cannot calculate thecorrect distance, depth, height and width of the hurdles.

Question 30.
“Receptors are modified neurons”. Justify the statement with examples of receptors in different sense organs. (March 2015)
Answer:
Receptors are modified neurons. Rods and cones in the eyes, auditory receptors in the ear, olfactory receptors in nose, skin receptors, taste receptors in the tongue are examples.

Question 31.
Suku feels difficulty of vision in dimlight
a) Identify the disease, from among the following.
i) Haemophilia
ii) Night blindness
iii) Glaucoma
b) What is the reason for this disease? (March 2012)
Answer:
a) Night blindness
b) Caused due to the deficiency of vitamin A

Question 32.
Light rays which reflect from the object are focussed on the retina and an image is formed.
a) Write the peculiarities of this image.
b) How do the images formed in the two eyes combine? What is its advantage?
Answer:
a) Small, inverted, real

b)

• Three-dimensional image of the object is formed due to the activity of the brain.
• Binocular vision becomes possible.

Question 33.
“The focal length of the lens in the eye can be adjusted to view distant and nearby objects.” Evaluate this statement and answer the questions given below.
a) When does this focal length of the lens decrease?
b) What is the change in the focal length of the lens while viewing distant objects? How does it become possible?
Answer:
a) While viewing nearby objects

b) Focal length increases, while viewing distant object the ciliary muscles relax ligaments stretch and the curvature of lens decreases. So the focal length decreases.

Question 34.
Analyse the statements given below and write reasons.
(a) Tears have antiseptic property
(b) We can see objects in three dimension.
Answer:
(a) Lysozyme the enzyme present in tears, destroys genus that enter the eyes.
(b) Binocular vision

Question 35.
Prepare two placards to be used in a rally organised by the school Science Club to propagate the importance of eye donation.
Answer:
Appropriate idea
Example: Let the eyes glow even after death! Eye donation great donation.

Question 36.
A fluid is formed in the eye just as the cerebrospinal fluid is formed in the brain.
(a) Name the fluid.
(b) What is its function?
Answer:
(a) Aqueous humor
(b) Nourishes the tissues of the eye

Question 37.
Select the correct statements.
(a) In dog highly sensitive olfactory receptors (3000 million) are found.
(b) Ears and special type of echo location organ seen in bat, helps in hunting and travelling.
(c) In snake, Jacobson’s organ helps to detect smell.
Answer:
(b) Ears and special type of echo location organ seen in bat, helps in hunting and travelling,
(c) In snake, Jacobson’s organ helps to detect smell.

Question 38.
The processes happening behind various responses made when seeing friends is given below. Arrange them in correct order?
(a) Then, instruction for responses are given to the muscles.
(b) Light rays from the friends’ enter the eyes and the image is formed.
(c) Various responses are formed as a result of muscular activities
(d) The impulse from the image reaches the brain through the eyes.
(e) The brain analyses this impulse and recognises the friends.
Answer:
b, d, e, a, c

Question 39.
Observe the picture and answer the questions given below.

(a) Identify the parts indicated as A, B, C, D.
(b) What is the role of the part indicated as D in the above process?
Answer:
(a) A – Tongue,
B – Papilla,
C – Taste bud,
D – Chemoreceptors

(b) Microvilli from each chemoreceptor, reach the minute pores present in the papilla. Saliva enters through this pore. Substances that give rise to taste are dissolved in saliva and stimulate chemoreceptors. The impulses produced by these molecules in the chemoreceptors reach the brain through the nerve and make the sense of taste.

Question 40.
It is because of its taste that we like food. Given below are the different stages of experiencing taste. Analyse and arrange them in the correct order.
a) Experience of taste
b) Causes impulses
c) Food particles dissolve in saliva
d) Reaches taste buds
e) Impulses reach the brain
f) Chemoreceptors get stimulated
Answer:
c, d, f, b, e, a

Question 41.
Complete the flowchart related to the sense of smell.

Answer:

Question 42.
Redraw the diagram and label the parts that perform the following functions:

a) The tissues in the eye receive nutrients and oxygen.
b) Regulares the amount of light entering the eye. (March 2016)
Answer:
a) Choroid layer
b) Iris\pupil

Question 43.
“Allow anyone to take my eyes after my death”. These are the words of Raju, who was admitted to the hospital after a serious accident.
a) How will you react to this statement?
b) Is it difficult to donate eyes after death?
c) Is it possible to donate an organ while alive? (March 2012)
Answer:
a) Raju is a noble and kind hearted person because Eye donation is a noble deed, as it brings happiness into the dark life of a blind person.

b) No, Eyes can be removed within 6 hours and transplanted to the patient by surgery.

c) Certain organs like, kidney, liver can be donated by a live donor.

Question 44.
Given below is the portion of a poster.

Don’t take high eye pressure easy. It may lead to blindness in future.

a) Which is the eye disease mentioned in the poster?
b) What is the reason for this condition?
c) What is the remedy for this disease?
Answer:
a) Glaucoma

b)

• Blockage of reabsorption of aqueous humour
• Increase in the pressure inside the eyes

c) Laser surgery

Question 45.
Observe the figure given below and answer the question.

a) Identify A, B
b) Which is the pigment in A?
c) Which is the eye disorder related to B?
Answer:
a) A – Rod cells,
B – Cone cells

b) Rhodopsin

c) Colour blindness

Question 46.
Analyse the illustration related to the power of accommodation of the eye and answer the questions.

a) Which figure indicates the change in the lens while viewing distant objects?
b) Give the reason for the change in the curvature of the lens in figure II than in figure 1.
Answer:
a) Figure 1

b)

• While viewing nearby objects
• Ciliary muscles contract
• Ligaments relax, so curvature of lens increases.

Question 47.
Vision is enabled when the impulse from the retina reaches the cerebrum through the optic nerve.
a) Draw a flow chart showing the pathway of light from cornea to retina.
b) There is no vision at the point where the optic nerve starts. Why?
Answer:
a) Light → Cornea → Aqueous humor → Pupil → Lens → Vitreous humor → Retina

b) Rod cells and cone cells are absent in the part from where the optic nerve starts photoreceptors are absent. So there is no vision.

Question 48.
Identify the word pair relationship and fill in the blanks.
a) Retina: The inner layer which has photoreceptors
__________ : The transparent anterior part of the sclera
b) Blind spot: The part from where the optic nerve begins
__________ : The part where the image has maximum clarity
c) _________ : Nourishes the tissues of the eye
Vitreous humor: Shape of the eye
Answer:
a) Cornea
b) Yellow spot
c) Aqueous humour

Question 49.
Choose the correct pairs related to the eye defects from the pairs given below.
a) Cataract – Reabsorption of aqueous humor does not occur
b) Glaucoma – Rectified by Replacing the lens
c) Colour blindness – Infection of conjunctiva
d) Cataract – Lens of the eye becomes opaque
e) Conjunctivitis – Rectified by Laser surgery
f) Glaucoma – Rectified by Laser surgery
g) Colourblindness – Inabilityto distinguish colours
Answer:
Correct pairs
d) Cataract – Lens of the eye becomes opaque
f) Glaucoma – Rectified by Laser surgery
g) Colour Blindness – Inability to distinguish colours

Question 50.
Complete the flowchart filling the blanks:
Sound waves → A → Tympanum → B → C → D ↓ Hearing ← F ← Auditory nerve ← Impulse ← E
Answer:
A. Pinna
B. Ear ossicles
C. Oval window
D. Cochlea
E. Hair cells
F. Cerebrum

Question 51.
Processes related to maintaining the equilibrium of the body are given below. Analyse and arrange them in the correct order.
a) Impulses are formed.
b) Muscular movements are coordinated.
c) Maintains the equilibrium of the body.
d) Sensory hair cells of the vestibular apparatus are stimulated.
e) Impulses reach the cerebellum.
f) Body movements create the movement of fluid inside the vestibule and semicircular canal.
Answer:
f → d → a → e → b → c

Question 52.
Observe the figure and answer the questions.

a) What does the figure indicate?
b) Identify X, Y
c) How do X and Y differ in function?
Answer:
a) Internal ear

b)

• X – Vestibular nerve
• Y – Auditory nerve

c)

• X – Transmits impulses form the vestibular apparatus to cerebellum
• Y – Transmits Impulses from the cochlea to the cerebrum

Question 52.
Redraw the diagram given below’. Identify the parts and label it.

a) Connects the middle ear with the pharynx.
b) Auditory receptor hair cells are present.
c) Separates the external ear from the middle ear.
Answer:

a) Eustachian tube
b) Cochlea
c) Tympanum

Question 53.
Prepare a short note on sensory diversity in organisms. (Hint: Bat, Hawk, Snake)
Answer:
Bat – Ears and special type of echo location organ helps in hunting and travelling.

Question 54.
Explain receptor potential and action potential.
Answer:
Electrical impulses are produced in receptors in response to external and internal stimuli. These impulses are known as receptor potential. When such impulses are in higher concentration, action potential is formed in the neurons associated with receptors. Action potential travels through neuron as nerve impulses.

Question 55.
The tube that connects the middle ear to the pharynx? What is its function?
Answer:
Eustachian tube. It helps to regulate the pressure inside the middle ear and protects the tympanum.

Question 56.
The flow chart sound waves passing through the ear is shown below. Complete it.
a) Ear Canal
b) …………………
c) Mallius
d) …………………
e) Stapes
f) …………………
g) Cochlea
h) Perilymph
i) …………………
j) Auditory receptors (Model 2012)
Answer:
b) Tympanum / Eardrum
d) Incus
f) Oval window
i) Endolymph

Question 57.
Correct the mistakes and rearrange the given flow chart of hearing process.
Ear canal → Cochlea → Eardrums Ear ossicles → Oval window → Auditory nerve
(March 2014)
Answer:
Ear canal → Eardrum → Ear ossicles → Oval window → Cochlea → Auditory nerve

Question 58.
Examine the terms given below and choose the parts related to the maintenance of equilibrium of the body.
Cerebrum, Eustachian tube, Sacule, Cochlea, Utricle, Vestibular nerve, Oval window, Cerebellum, Semi circular canals
Answer:
Sacule, Utricle, Vestibular nerve, Cerebellum.

Question 59.
Observe the picture and answer the questions given below.

(a) Identify the parts indicated as A, B.
(b) What is the role of the part indicated as C in the above process?
Answer:
(a) A – Group of olfactory nerves B – Olfactory receptor neurons

(b) While breathing, the particles responsible for smell enter the nasal cavity. Then it gets dissolved in the mucus produced by mucus membrane. Millions of olfactory neurons in the mucus membrane get stimulated by special olfactory particles.

Question 60.
Convert the following chart of sensing smell to a flow chart of feeling taste.
Olfactory particles dissolve in mucus → Stimulation in olfactory receptors → Formation of impulse → Transmission of impulses through nerve → Olfactory centre in the cerebrum → Experiencing smell
Answer:
Food particles dissolve in the saliva → Taste receptors (taste buds) are stimulated → Impulses form and transmit through nerves → Brain → Experience of taste.

Question 61.
We are unable to recognize smell and taste of food when we have cold. Can you say the reason?
Answer:
Smell influences tasting. During cold, excess mucus will be produced in the nasal cavity. This will obstruct the normal stimulation of olfactory receptors and hence, we are unable to recognize smell and feel the food tasteless.

Question 62.
Select correct answer from the box.
Hyper metropia, Myopia, Night blindness, Colour blindness, Cataract, Glaucoma, Conjunctivitis, Xerophthalmia
a) Disorder related to the eye lens?
b) Disorder related to the aqueous humour?
c) Disorders due to the difference in the size of eyeball?
d) Disorder that can be rectified by convex lens?
e) An infection?
f) Genetic disorder?
g) Disorder due to the deficiency of vitamin A?
h) Disorder due to the prolonged deficiency of vitamin A?
Answer:
a) Cataract.
b) Glaucoma
c) Hyper metropia and myopia
d) Hyper metropia
e) Conjunctivitis
f) Colourblindness
g) Night blindness
h) Xerophthalmia

Question 63.
Redraw the picture.
a) Label the parts A, B and C.
b) Write down the functions of B, C & D. (March 2013)

a) A – Lens
B – Aqueous chamber
C – Layer of the eye

b) B – Aqueous chamber
This is the chamber between lens and the cornea. It is filled with a watery fluid called aqueous humour which supplies nutrients and oxygen to the cells of the cornea and the lens.

C – Layer of the eye
Retina, the innermost layer of the eyeball it imparts the firmness to the eye ball.

D – Vitreous chamber
This is the large chamber seen between the lens and the retina which is filled with the jelly like vitreous humor. This helps to maintain the shape of the eye ball.

Question 64.
Copy the figure. Label the name of following parts on the figure.

a) Part on which image form.
b) Circular anterior part of the choroid layer.
c) The main part which regulate the focal length of light rays. (Model 2012)
Answer:

Question 65.
Rearrange the flowchart related to sense of vision. Light → Lens → Pupil → Vitreous humor → Aqueous humor → Optic nerve → Retina → Cerebrum → Cornea → Impulse → Sense of vision Answer:
Light → Cornea → Aqueous humor → Pupil → Lens → Vitreous humor → Retina → Impulse → Optic nerve → Cerebrum → Sense of vision

Question 66.
The diagram given below shows the structure of ear:

a) Redraw the diagram.
b) Label the parts A, B, C, D.
c) Write down the name and function of E and F. (Model 2014)
Answer:

b) A – tympanum (ear drum)
B – Auditory nerve
C – Ear ossicles
D – Eustachian tube

c) E – Semicircular canal – balancing
F – Cochlea – hearing

Question 67.
Prepare a flowchart on how smell is effected.
Answer:
While breathing, the particles responsible for smell
enter the nasal cavity. → The particles gets dis-solved in the mucus produced by mucus membrane → Olfactory neurons in the mucus membrane get stimulated by special olfactory particles. → Receptors generate impulses, and they travel through the olfactory nerve to reach the part of the brain recognising smell → The sense of smell is effected.

Question 68.
Complete the table.

Organisms	Sensory diversity
Euglena	……………………. (a) ………………….
……………………. (b) ………………….	Highly sensitive olfactory receptors (300 million) are found.
Insects	……………………. (c) ………………….
……………………. (d) ………………….	Detects the presence of chemicals in the surroundings and move against them

Answer:

Organisms	Sensory diversity
Euglena	The eyespot (stigma) helps to detect light and move towards it
Dog	Highly sensitive olfactory receptors (300 million) are found.
Insects	The compound eye made up of Ommatidia. The Antenna helps to detect smell and touch.
Amoeba/Bacteria	Detects the presence of chemicals in the surroundings and move against them

Question 69.
How are responses formed in organisms?
Answer:
Responses are formed due to various biological and chemical processes that takes place in the body of organisms.

Question 70.
What are the processes happening behind various responses made when seeing friends?
Answer:

• Light rays from the friends’ enter the eyes and the image is formed.
• The impulse from the image reaches the brain through the eyes.
• The brain analyses this impulse and recognises the friends.
• Then, instruction for responses are given to the muscles.
• Various responses are formed as a result of muscular activities.

Question 71.
What are stimuli?
Answer:
Stimuli are the circumstances that lead to responses in living beings. They can be divided into external stimuli and internal stimuli.

Question 72.
What are Sensory Receptors?
Answer:
Stimuli are recognised by the body through specialised cells or nerve endings. They are known as Sensory Receptors.

Question 73.
How does our body respond to external and internal stimuli?
Answer:
Electrical impulses are produced in receptors in response to external and internal stimuli. These impulses are known as receptor potential. When such impulses are in higher concentration, action potential is formed in the neurons associated with receptors. Action potential travels through neuron as nerve impulses. Nerve impulses reach the related parts of the brain and form appropriate response instructions. Muscles and glands respond to these instructions accordingly.

Question 74.
Write a short note on senses?
Answer:
Senses that can be recognised through receptors are divided into two types: general senses and special senses. The receptors in skin, muscles, joints, internal organs and blood vessels help to detect general senses such as touch, pain, heat, pressure etc. But the receptors concentrated only in certain organs help to recognise specific senses such as vision, hearing, taste and smell, etc.

Question 75.
The tongue can detect taste, but the ears can’t. What could be the reason?
Answer:
Different sense organs have different types of receptors that are specialized to detect specific stimuli. The tongue has chemoreceptors that detect chemical substances in food, helping us to taste. The ears, on the other hand, have auditory receptors that are specialized to detect sound vibrations, not chemicals.

So, the tongue can detect taste because it has the right type of receptors, while the ears do not.

Question 76.
Describe the structure of eye?
Answer:

Layers of the eye – Sclera (outer layer) – provides firmness and protection to the eye
Associated parts – Cornea
Characteristics and function – The transparent anterior part of the eye. Allows light to enter the eye.
Layers of the eye – Choroid (middle layer) – Provides oxygen and nutrients to the inner layer of retina and regulates temperature.
Associated parts – Ciliary muscles
Characteristics and function – Adjusts the curvature of the lens.
Associated parts – Iris
Characteristics and function – Two types of muscles in the iris regulate the size of the pupil depending on the intensity of light. Iris contains the pigment called melanin. Melanin gives the iris its characteristic colour as well as absorbs ultraviolet rays. Regulates the amount of light.
Associated parts – Convex lens
Characteristics and function – Forms a small, real and inverted image of the object on the retina.
Layers of the eye – Retina (inner layer) – Contains photoreceptor cells. The image is formed.
Associated parts – Layer of photoreceptors
Characteristics and function – The photoreceptor cells called rod cells recognise objects in both dim light and in shades of black and white. The cone cells provide vision in intense light and also help in recognising colours.
Associated parts – Bipolar cell layer
Characteristics and function – Transmits impulses from the photoreceptors to ganglion cells.
Associated parts – Ganglion cell layer
Characteristics and function – Transmits impulses from bipolar cells to the optic nerve.

Question 77.
Differentiate between Blind Spot and Yellow Spot
Answer:
There are no photoreceptor cells in the retina where the optic nerve originates. This part having no vision is known as the blind spot. The yellow spot (macula) is seen in the middle of the retina where cone cells are abundant.

Question 78.
What is aqueous humor ? Write its function.
Answer:
The aqueous chamber is seen between the cornea and lens. The watery aqueous humor is present here. It oozes out from the blood like tissue fluid and is reabsorbed into the blood. This is how the pressure in aqueous chamber is regulated. Lens and cornea get oxygen and nutrients from this fluid.

Question 79.
What is vitreous humor ? Write its function.
Answer:
The vitreous chamber lies in between the lens and the retina. The transparent jelly like vitreous humor present there maintains the shape of the eyeball.

Question 80.
What is pupil?
Answer:
Iris is the part seen behind the cornea. The pupil is the aperture seen at the centre of the iris. The normal size of the pupil is from 2 to 3 mm. When the size of the pupil increases, it becomes possible to direct 16 times more light on to the retina than normal.

Question 81.
Explain the structure of lens?
Answer:

The lens has three main parts. They are an elastic membrane called the capsule, within which are the lens fibres and the epithelium, which is located solely in the anterior part, between the lens fibres and the capsule. It is the epithelium that continuously produces lens fibres throughout an individual’s lifetime. The main structural component of the lens is a protein called crystallin. The lens derives nutrients from the aqueous humour. Age-related changes affect the flexibility and transparency of the lens as well as vision.

Question 82.
In eyes lens got attached to the ciliary muscles through ligaments. What is the importance of this arrangement?
Answer:
In the eye, the lens is connected to the ciliary muscles through ligaments called suspensory ligaments. This arrangement is important because it helps the eye to focus on objects at different distances, a process known as accommodation. When the ciliary muscles contract or relax, they change the tension on the ligaments, which in turn changes the shape of the lens. This allows the lens to become thicker to focus on nearby objects and thinner to focus on distant objects, helping us see clearly at all distances.

Question 83.
What is power of accommodation?
Answer:
The ability of the eye to foucs images of both near and distant objects accurately on the retina is called the power of accommodation. This is achieved by changing curvature of the lens, by the actions of the ciliary muscles.

Question 84.
What are the change in the activities of the parts of the eye while viewing near objects and distant objects?
Answer:
While viewing nearby objects
Ciliary muscles contract, Ligaments relax, Curvature of lens increases (Lens becomes thicker), Focal length decreases.

While viewing distant objects
Ciliary muscles relax, Ligaments stretch, Curvature of lens decreases (Lens becomes thinner), Focal length increases.

Question 85.
What are the photoreceptors seen in retina? Write its peculiarities?
Answer:
The rod cells and the cone cells are the photoreceptors seen in retina. Rod cells are cylindrical and cone cells are cone shaped. Rod cells are about more than 9 crores in number and cone cells are about 45 lakhs. Rod cells contain the pigment called rhodopsin and in cone cells is photopsin. The components of both pigments include a protein namely opsin and retinal, formed from Vitamin A. However, the chemical structure of retinal is different in rhodopsin and photopsin.

Question 86.
How does the perception of darkness and light occur through the action of photoreceptors and bipolar cells?
Answer:

• Glutamate acts as the primary neurotransmitter in photoreceptors. Variations in glutamate production are responsible for the perception of darkness and light.
• In the dark, photoreceptors continuously produce glutamate. On bipolar cells (those that sense light) are inactivated and off bipolar cells (those that sense darkness) are activated. Off bipolar cells that indicate the absence of light form impulses that reach the brain through the optic nerve, creating a sense of darkness.
• In the presence of light, photorecptors do not produce glutamate. On bipolar cells become active and off bipolar cells become inactive. On bipolar cells that indicate the presence of light form impulses that reach the brain through the optic nerve, creating a sense of vision.

Question 87.
How coloured vision is possible?
Answer:
In the retina, there are three types of cone cells recognise primary colours. S – cones show better sensitivity at short wavelengths (blue light), M – cones at medium wavelengths (green light) and L – cones at longer wavelengths (red light). Colour vision is made possible when the three types of cones get stimulated in varying proportions when exposed to coloured light depending upon the intensity and wavelength of light. When red and green cones are stimulated together, the perception of yellow colour is formed. The stimulation of all the three types of cones creates the sensation of white light.

Question 88.
What is binocular fusion? What are its advantages?
Answer:

Binocular fusion
Since each eye receives light from different angles, there will be two slightly different images on the retina. These two images are sent to the visual cortex in the brain. The brain compares these images and combines them(fusion). This process is known as binocular fusion. This will help to determine the difference between the two images. Thus, we get 3D vision. It enables to understand how distant or near objects are, and also to perceive depth.

Question 89.
Prepare a short note on World Sight Day.
Answer:
World Sight Day is observed on the second Thursday of October. The World Health Organisation (WHO) and the International Agency for the Prevention of Blindness (IAPB) call for the observance of this day to raise awareness on the eye healthcare. This also includes reducing screen time and encouraging regular eye tests to care for children’s vision. WHO eyes, a free application available in 14 languages enables free eye test for ages 8 and above. Some vision problems can be corrected with less expensive methods such as spectacles and cataract surgery.

Question 90.
What ways that can be implemented to protect the eye from various disorders and diseases?
Answer:

• Wash the eyes frequently, with clean water.
• Eat food rich in Vitamin A
• Avoid touching or rubbing the eyes with dirty hands to prevent infections.
• Use proper lighting while reading or studying to avoid eye strain.
• Take regular breaks while using screens (follow the 20-20-20 rule: every 20 minutes, look at something 20 feet away for 20 seconds).
• Wear protective eyewear (like safety goggles) while working in dusty environments or while playing sports.
• Avoid prolonged screen time and reduce screen brightness when not needed.
• Do not use expired or unprescribed eye drops or ointments.
• Go for regular eye check-ups, especially if there are signs of vision problems.
• Wear sunglasses with U V protection when stepping out in bright sunlight.
• Stay hydrated and get enough sleep to reduce eye dryness and fatigue.

Question 91.
Donating the eye is a noble act? Explain.
Answer:
Donating eyes can give vision to two blind people. Cornea gets surgically transplanted. It is beneficial for those who have lost their vision due to the damage of the cornea.

Question 92.
What are the devices that are used in eye tests?
Answer:
There are several charts used to test visual acuity. Among them, the commonly used one is Snellen Chart. It consists of rows of letters or symbols that decrease in size from top to bottom. In the test, the person stands twenty feet away and reads the smallest line that can be clearly seen with one eye. The results are recorded as a fraction. This simple but effective test is an important part of routine eye test. There are many such charts and symbols.

In addition to this, many modem devices are used for eye test. Examples include Retinoscopes, Tonometers and Ishihara plates.

Question 93.
What do the numerator and denominator of the fraction in an eye test result using Snellen chart indicate?
Answer:
In an eye test using the Snellen chart, the result is usually written as a fraction like 6/6 or 6/18. In this fraction, the numerator (top number) indicates the distance from which the person is standing during the test, usually 6 meters. The denominator (bottom number) shows the distance at which a person with normal vision can read the same line on the chart. For example, a result of 6/6 means the person can read at 6 meters what a normal person can read at 6 meters, this is considered nonnal vision. A result of 6/18 means the person can read at 6 meters what a person with normal vision can read at 18 meters, this indicates weaker eyesight.

Question 94.
What are the functions of ear?
Answer:
Hearing is the combined experience of the ears and the brain. The sense of hearing also leads to responses. The human ear also plays a major role in maintaining the balance of the body.

Question 95.
What are the function of pinna?
Answer:
Directs the sound waves into the auditory canal. Helps to identify the direction from which sound is produced. Protects the auditory canal to some extent from foreign particles.

Question 96.
What are the peculiarities and functions of the auditory canal?
Answer:
It directs sound waves to the tympanum and protects the tympanum from foreign particles. The hair inside the auditory canal, earwax and sebum secreted by glands in its wall help to prevent dust and germs from entering the ear. Like tears, ear wax also has disinfectant properties.

Question 97.
What are the peculiarities and function of the tympanum?
Answer:
Tympanum or eardrum is 9 – 10 mm in diameter and has only 0.1 mm thickness. The tympanum vibrates in accordance with the sound waves.

Question 98.
What are the peculiarities and function of the eustachian canal?
Answer:

The eustachian canal is a long tube that is 4 cm long that connects the middle ear to the pharynx. Normally it is closed, but it opens during chewing, blowing the nose etc. It helps to balance the pressure on both sides (middle ear and the atmospheric air in the outer ear) of the tympanum. It also facilitates the flow of mucus and fluids from middle ear to the pharynx.

Question 99.
Explain the sense of hearing?
Answer:

Sound waves vibrate the tympanum. From there the vibration passes through the ear ossicles and then vibrates the oval window. The structure of the oval window is also similar to that of the tympanum. The cochlea, having the shape of a snail shell, has three chambers, oval window is the membrane that covers the opening towards the upper chamber. The upper and lower chambers are filled with a fluid called perilymph. The middle chamber is filled with endolymph. The Organ of Corti where the auditory receptors are present is situated in the basilar membrane between middle and lower chambers. The vibrations that reach the hair cells present here generate impulses. These impulses reach the brain through auditory nerve resulting in the sense of hearing

Question 100.
What is the role of the ear in maintaining balance?
Answer:
The part of the inner ear that maintains body balance is the vestibular system, which includes three semicircular canals, vestibule and hair cells. The endolymph present in the canals, which are arranged perpendicular to each other, moves with the rotational movement of the head. As a result of this movement, the hair cells present here get stimulated and impulses are formed. The utricle and saccule of the chamber called the vestibule also contain hair cells. The linear movement of the head generates impulses in these hair cells. When the impulses reach the brain through the vestibular nerve, the brain maintains body balance by receiving impulses from the eyes and muscles as well.

Question 101.
Write a short note on hearing impairments?

Answer:

• Hearing impairments occur due to many reasons.
• Sound that travels in the form of waves can be transmitted only through a medium.
• A sound that can be heard in a condition of complete silence is represented as zero decibel.
• For every 10 decibels, the intensity of the sound increases tenfold.
• In a normal conversation, intensity of the sound will be between 40 and 50 decibels. It can be up to 60 decibels, while speaking loudly.
• The normal sound of the honking of a car horn is 70 decibels, while that of an air horn is 100 – 110 decibels.
• Intensity of noise above 80 decibels is extremely annoying.
• Noise pollution is a danger that is most harmful and unfortunately, the most neglected of all the environment pollutions that we face today.
• Hearing of loud noise (above 85 decibel) for a short time and less noise with a lesser intensity (below 55 decibel) for a very very long time can cause permanent hearing impairment.

Question 102.
How smell is effected?
Answer:

While breathing, the particles responsible for smell enter the nasal cavity. Then it gets dissolved in the mucus produced by mucus membrane. Millions of olfactory neurons in the mucus membrane get stimulated by special olfactory particles. Receptors generate impulses, and they travel through the olfactory nerve to reach the part of the brain recognising smell, and the sense of smell is effected.

Question 103.
How taste is detected?
Answer:

A taste bud will have about 100 chemoreceptors. Microvilli from each chemoreceptor, reach the minute pores present in the papilla. Saliva enters through this pore. Substances that give rise to taste are dissolved in saliva and stimulate chemoreceptors. The impulses produced by these molecules in the chemoreceptors reach the brain through the nerve and make the sense of taste.

Question 104.
What are the main tastes we can detect?
Answer:
The main tastes we recognise are sweet, sour, salty, pungent, bitter and umami.

Question 105.
What are the receptors in the skin?
Answer:
There are various receptors present in skin for carryout different functions. They are,

Part	Name	Functions
1	Independent nerve endings	Pain, temperature fluctuations
2	Merkel disc	Touch, pressure and movement of hair
3	Meissner corpuscles	Shape, quantity and structure of objects
4	Krause end bulbs	Cold, touch
5	Rufini end organ	Intense touch, pressure, heat
6	Root hair plexus	Helps to find out the movement of hair
7	Pacinian corpuscles	Vibration, touch with a high frequency

Question 106.
Prepare a short note on the sensory diversity in organisms?
Answer:
Sensory diversity in organisms

• Amoeba/Bacteria – Detects the presence of chemicals in the surroundings and move against them.
• Euglena – The eyespot (stigma) helps to detect light and move towards it.
• Insects – The compound eye made up of Ommatidia. The Antenna helps to detect smell and touch.
• Bat – Ears and special type of echo location organ helps in hunting and travelling.
• Hawk – Eyes with high vision, systems for long distance vision and detecting ultra violet radiation.
• Snake – Jacobson’s organ helps to detect smell.
• Dog – Highly sensitive olfactory receptors (300 million) are found.
• Human senses are the powerful tools that connect us to the world around us.