Selina ICSE Class 10 Biology Solutions Chapter 8 The Nervous System

Multiple Choice Type
(Select the most appropriate option in each case).

Question 1: The insulating sheath covering the neural axon is called.
(a) plasmalemma
(b) neurolemma
(c) dura mater
(d) pia mater

Question 2: Which one of the following pairs of brain part and its function is not correctly matched?
(a) Cerebrum – Memory
(b) Cerebellum – Balance of body
(c) Medulla oblongata – controls activites of internal organs
(d) Pons – Consciousness

Question 3: A mixed nerve is one which
(a) carries sensations from 2 or more different sense organs
(b) contains both sensory and motor fibres
(c) has a common root but braches into two or more nerves to different organs
(d) has two or more roots from different parts of brain.

Very Short Answer Type:

Question 1: Name the following:
(a) The fluid that is present inside and outside the brain.
(b) The junction between two nerve cells
(c) The part of the brain which is concerned with memory
(d) The part of the human brain which controls body temperature.
Solution 1:
(a) Cerebrospinal fluid
(b) Synapse
(c) Cerebrum
(d) Hypothalamus

Question 2: Note the relationship between the first two words and suggest the suitable word/words for the fourth place.
(a) Stimulus: Receptor:: Impulse: …………….
(b) Cerebrum: Diencephalon:: Cerebellum: ……………….
(c) Receptor: Sensory nerve:: Motor nerve: ……………….
Solution 2:
(a) Stimulus: Receptor:: Impulse: Effectors
(b) Cerebrum: Diencephalon:: Cerebellum: Medulla oblongata
(c) Receptor: Sensory nerve:: Motor nerve: Effector

Question 3: Complete the following statements by choosing the correct alternative from the choice given in brackers:
(a) The dorsal root ganglion of the spinal cord contains cell bodies of (motor/sensory/intermediate) neurons.
(b) Cerebellum is the part of the brain which is responsible for
(i) conducting reflexes in the bosy
(ii) maintain posture and equilibrium
(iii) controlling thinking memory & reasoning
(c) Reflex action is controlled by
(i) brain (ii) spinal cord
(iii) autonomic (iv) peripheral nervous system
Solution 3:
(a) Sensory
(b) Maintaining posture and equilibrium
(c) Spinal cord

Short Answer Type:

Question 1: Mention where in human bosy are the following located and state their main function:
(a) corpus callosum
(b) central canal
Solution 1:
(a) Corpus Callosum – It is found in the frontal lobe of the brain. It connects the two hemispheres of the brain and conveys information from one to the other.
(b) Central canal – It’s in the middle of the spinal cord. It goes on and on with the cavities of the brain. It’s made up of cerebrospinal fluid and works as a shock absorber. It also aids in the exchange of materials between neurons.

Question 2: State whether the following statements are true (T) or false (F).

(a) The main component of the white matter of the brain is perikaryon

(b) The arachnoid layer fits closely inside the pia mater.

(c) A double chain of ganglia, one on each side of the nerve cord belongs to the spinal cord.

(d) Dura mater is the outermost layer of the meninges.

Question 3: Differentiate between following pairs with reference to the aspect in brackets.
(a) cerebrum and cerebellum (function)
(b) sympathetic nervous system and para – sympathetic nervous system (overall effect on body)
(c) Sensory nerve and motor nerve (direction of impulse carried)
(d) medulla oblongata & cerebellum (function)
(e) cerebrum and spinal cord (arrangement of cytons and exons of neurons).
Solution 3:

(a) Cerebrum	Cerebellum
All voluntary acts are controlled by the cerebrum. It gives us the ability to think, reason, plan, and memorise.	The cerebellum, on the other hand, is responsible for maintaining body equilibrium and coordinating muscular activity.
(b) Sympathetic Nervous System	Parasympathetic Nervous System
The sympathetic nervous system prepares the body to fight the abnormal state with violence.	After a violent act, the parasympathetic nervous system is concerned with restoring normal conditions.
(c) Sensory Nerve	Motor Nerve
Sensory nerves carry impulses from receptors, such as sense organs, to the brain and spinal cord.	The motor neuron transports impulses from the brain or spinal cord to effector organs like muscles or glands.
(d) Medulla Oblongata	Cerebellum
Internal organs and many other involuntary functions are controlled by the medulla oblongata.	The cerebellum, on the other hand, is responsible for maintaining body equilibrium and coordinating muscular activity.
(e) Cerebrum	Spinal Cord
The cortex (outside area) contains the grey matter containing cytons, while the medullary region contains the white matter containing axons (inner region).	The medullary area, which contains cytons, is on the inner side of the brain, whereas the cortex, which contains axons, is on the outside side.

Question 4: Given below are two structures, write their special functional activity.
(a) cerebellum and …………….
(b) Myelin sheath and ……………
Solution 4:
(a) Cerebellum maintains balance of the body and coordinates muscular activity.
(b) Myelin sheath acts like an insulation and prevents mixing of impulses in the adjacent axons.

Question 5: Write the functions of the following:
(a) synapse (b) Association neuron
(c) medullary sheath (d) Medulla obiongata
(e) cerebellum (f) Cerebrospinal fluid
Solution 5:
(a) Synapse: It’s a space between one neuron’s axon terminal and the adjacent neuron’s dendrites. It is responsible for transmitting nerve impulses from one neuron to the next.
(b) Association Neuron: It bridges the gap between sensory and motor neurons.
(c) Medullary sheath: It provides insulation and prevents mixing of impulses in the adjacent axons.
(d) Medulla Oblongata: It regulates internal organ functions such as peristalsis, respiration, and a variety of other involuntary processes.
(e) Cerebellum: It keeps the body in balance and coordinates muscular activity.
(f) Cerebrospinal Fluid: It functions as a shock absorber and protects the brain.

Question 6: What do we refer to in the nervous system when we say:
(a) sensory, motor and mixed ………………..
(b) somatic and autonomic …………………..
(c) Natural and conditioned …………………
(d) sensory, motors and association ……………….
(e) Gray and white ………………………………
Solution 6:
(a) Sensory, motor and mixed nerves
(b) Somatic and autonomic nervous system
(c) Natural and conditioned reflexes
(d) Sensory, motor and association neurons
(e) Gray and white matter

Question 7: Rearrange the following in correct sequence pertaining to what is given within brackets at the end.
(a) Effector …….. sensory neuron ………. Receptor…….. motor neuron……….
Stimulus……. central nervous system… Response (Reflex arc)
(b) repolarization……. Depolarization…….. Resting….. (polarised) (during conduction of nerve impulse through a nerve fibre)
(c) axon endings ……… nucleus …….. Dendrites ……… axon…….. perikaryon ……….
Dendron (Neutron structure)
(d) diencephalon ………. Cerebellum …….. medulla oblongata ………. Pons Cerebrum
……. mid-brain (sequence of parts of human brain).
Solution 7:
(a) Stimulus -> receptor -> sensory neuron -> central nervous system -> motor neuron ->
Effector -> response
(b) Resting -> depolarization -> repolarization
(c) Dendrites -> Dendron -> perikaryon -> nucleus -> axon -> axon endings
(d) Cerebrum -> diencephalon -> mid-brain -> cerebellum -> pons -> medulla oblongata

Long Answer Type:

Question 1: (a) What is meant by reflex action?
(b) State whether the following are simple reflexes conditioned reflexes or neither of the two:
(i) Sneezing: …………….
(ii) Blushing: ……………….
(iii) Contraction of eye pupil: …………………..
(iv) Lifting up a book: …………………..
(v) Knitting without looking: …………………..
(vi) sudden application of brakes of the cycle on sighting an obstacle in front …………….
Solution 1:
(a) Reflex action is an autonomic, quick and involuntary action in the body brought about by a stimulus.
Example Type of Reflex
(i) Sneezing Simple
(ii) Blushing Simple
(iii) Contraction of eye pupil Simple
(iv) Lifting up a book Conditioned
(v) Knitting without looking Conditioned
(vi) Sudden application of brakes of the cycle on sighting an obstacle in front Conditioned

Question 2: What are the advantages of having a nervous system?
Solution 2:
The advantages of having a nervous system are as follows:
(a) Aids in the communication of our various body parts.
(b) Sense organs keep us information about the outer world.
(c) Allows us to recall, think, and reason.
(d) Regulates and harmonizes all voluntary muscular movements such as running, holding, and writing.
(e) It helps us to identify a signal rapidly and then communicate and coordinate with both the external and internal surroundings in order to respond appropriately.

Question 3: Why do you call the spinal cord and the brain as the central nervous system?
Solution 3:
The skull and the vertebral column, respectively, house the brain and spinal cord. They play a crucial role because they are in charge of all body functions. For the correct response, a stimulus from any region of the body is always transmitted to the brain or spinal cord. The central nervous system also produces a response to a stimulus. The brain and spinal cord are hence referred to as the central nervous system.

Question 4: What is the difference between reflex action and voluntary action?
Solution 4:

Reflex Action	Voluntary Action
Reflex actions are involuntary actions which occur unknowingly.	Voluntary actions on the other hand are performed consciously.
Commands originate in the spinal cord, autonomic nervous system and a few in the brain as well.	Commands originate in the brain.

Question 5: Draw a labelled diagram of a myelinated neuron.
Solution 5:

Question 6: During a street fight between two individuals, mention the effects on the following organs by the autonomous nervous system, in the table given below : (one has been for you as an example).

Organ	Sympathetic System	Parasympathetic System
e.g. Lungs	Dilates bronchi and bronchioles	Constricts bronchi and bronchioles
1. Heart
2. Pupil
3. Salivary gland

Solution 6:

Organ	Sympathetic System	Parasympathetic System
e.g. Lungs	Dilates bronchi and bronchioles	Constricts bronchi and bronchioles
1. Heart	Accelerates heartbeat	Retards heartbeat
2. Pupil	Dilates	Constricts
3. Salivary gland	Inhibits the secretion of saliva causing the drying of the mouth	Stimulates the release of saliva

 Structured / Application/Skill Type:

Question 1: Two hungry boys (A and B) enter a restaurant and find a table decorated as follows:

Boy B starts salivating but not A. Explain the reason for this difference.
Solution 1:
A conditioned reflex is one that develops as a result of experience or learning. When you chew or eat food, saliva starts to flow. As a result, this reaction will be triggered by more than just the sight or smell of food. The flavour of food is actually required by the brain. Boy B began to salivate since, unlike boy A, he must have tasted the dish before.

Question 2: Given below are a few situations. What effective change will occur in the organ/body part mentioned and which part (sympathetic or parasympathetic) of the autonomic nervous system brings it about?

Situation	Organ/body part	Change/action	Part of autonomic nervous system involved
1. You have entered a dark room	Eye
2. Your body is consuming lot of glucose while running a race	Liver
3. You are chewing a tasty food	Salivary gland
4. You are running a race	Adrenal gland
5. You are retiring to bed for sleep	Heart
6. You are shivering in intense cold	Body hairs

Solution 2:

Situation	Organ/body part	Change/action	Part of autonomic nervous system involved
1. You have entered a dark room	Eye	Pupil dilates	Sympathetic
2. Your body is consuming lot of glucose while running a race	Liver	Glycogen is converted into glucose in liver	Sympathetic
3. You are chewing a tasty food	Salivary gland	Salivation increases	Parasympathetic
4. You are running a race	Adrenal gland	Release of adrenaline and noradrenaline increases	Sympathetic
5. You are retiring to bed for sleep	Heart	Heart rate slows down	Parasympathetic
6. You are shivering in intense cold	Body hairs	Hair raised	Sympathetic

Question 3: Given below is the partially incomplete scheme of the components of peripheral nervous system. Fill up the blanks numbered (1) – (8):

Solution 3:
1. Central Nervous System
2. Autonomic
3. 12
4. spinal
5. 31
6. Dilates
7. Constricts
8. Liver

Review Questions:
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?
(a) Conjunctiva
(b) Cornea
(c) Choroid
(d) Ciliary muscles

Question 2: Which part of our ear is shaped like a snail shell?
(a) Semi circular canals
(b) Cochlea
(c) Stapes
(d) Eustachian tube

Question 3: The three parts of human ear contributing in hearing are-
(a) cochlea, ear ossicles and tympanum
(b) semicircular canals, utriculus and sacculus
(c) eutachian tube, tympanum and utriculus
(d) perilymph, ear ossicle and semicircular canals.

Question 4: The region in the eyes where the rods and cones are located is the
(a) retina
(b) cornea
(c) choroid
(d) 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 outermost covering layer of the brain
(e) The tube which connects the cavity of the middle ear with the throat
(f) The part of the eye responsible for its shape.
(g) The nerves which transmit impulse from ear to the brain
(h) The photoreceptors found in the retina of the eye.
(i) The eye defect caused due to shortening of the eye ball from front to back.
Solution 1:
(a) Rhodopsin
(b) Eustachian tube
(c) Hammer
(d) Dura mater
(e) Eustachian tube
(f) Cornea
(g) Auditory nerves
(h) Rods and cones
(i) Hypermetropia

Question 2: Note the relationship between the first two words and suggest the suitable word/words for the fourth place.
(a) Cones : Iodopsim :: Rods : ……………….
(b) sound : ear drum :: Dynamic balance : ……
Solution 2:
(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? write the correct matching pairs-

Column I	Column II
(i) The blind spot	(a) colour of the eye
(ii) the yellow spot	(b) shape of the lens
(iii) Ciliary muscle	(c) protective covering of the brain
(iv) Iris	(d) basic unit of brain
(v) Meninges	(e) free of rod cells
	(f) vitreous humour
	(g) centre of the retina
	(h) no sensory cells

Solution 3:

Column I	Column II
(i) The blind spot	(h) no sensory cells
(ii) the yellow spot	(g) centre of the retina
(iii) Ciliary muscle	(b) shape of the lens
(iv) Iris	(d) basic unit of brain (e) free of rod cells
(v) Meninges	(c) protective covering of the brain

Short Answer Type:

Question 1: Differentiate between members of each of the following pairs with reference to what is asked in brackets.
(a) Myopia and hyperopia (cause of the defect)
(b) Rods and cones (sensitivity)
(c) Semi-circular canal and cochlea (Senses perceived)
(d) Rod and cone cells (pigment contained)
(e) Dynamic balance and static balance (Definition)
Solution 1:
(a) Myopia is caused by a lengthening of the eyeball from front to rear or a lens that is excessively bent.
Hyperopia is caused by either a front-to-back shortening of the eyeball or a lens that is overly flat.
(b) Rods are sensitive to low light, but they are unaffected by colour. Cones are responsible for colour vision and are sensitive to intense light.
(c) The cochlea is in charge of hearing and is capable of perceiving the senses of hearing.
(d) The semicircular canals are in charge of perceiving the senses in order to keep the body balanced.
(e) Rhodopsin is found in rod cells, while iodopsin is found in cone cells.
(f) Dynamic balance occurs when the body is moving, whereas static balance occurs when the body is in a fixed posture with respect to gravity.

Question 2: State whether the following statements are True (t) or False, correct them by changing any one single word in each.
(a) Deafness is caused due to rupturing of the pinna
(b) Semi circular canals are concerned with static (positional) balance.
Solution 2:
(a) False: Deafness is caused due to rupturing of the eardrum.
(b) False: Semicircular canals are concerned with dynamic balance.

Question 3: Mention, where in living organisms are the following located and state their main functions:
(a) Fovea centralis (b) Organ of corti
Solution 3:
(a) The fovea centralis is placed near the centre of the eyeball at the back of the eye. It is the brightest vision as well as the colour vision region.
(b) The corti organ is found in the inner ear. It is made up of sensory cells that process sound.

Question 4: Mention if the following statements are true (T) or false (F) Give reason.

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

(b) Ciliary muscles regulate the size of the pupil

(c) yellow spot of the retina is the region of colour vision

(d) The auditory nerve is purely for perceiving sound

(e) Malleus incus and stapes are collectively called the ear ossicles

(f) Flavour and taste are one and the same thing.

(g) short-sightedness and hyperopia are one and the same thing

(h) Blind spot is called so because no image is formed on it.

Question 5: 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
Solution 5:
(a) Auditory canal, tympanum, ear ossicles, oval window, cochlea
(b) Conjunctiva, cornea, lens, retina, optic nerve

Question 6: Given below are certain structures. Write against them their functional acivity.
(a) organ of corti and ……………….
(b) Olfactory nerve and ……………..
(c) retina and ……………………….
d) Taste bud and …………………..
Solution 6:
(a) Organ of Corti and hearing
(b) Olfactory nerve and smell
(c) Retina and vision
(d) Taste bud and taste

Question 7: Answer the following:
(a) What is a lacrimal gland?
(b) In what two ways is the yellow spot different from the blind spot?
(c) Name an old age eye defect. What happens in it?
(d) What is meant by power of accommodation of the eye?
(e) Mention the characteristics of the image that falls on the retina of the eye.
Solution 7:
(a) A tear gland positioned on the top sideward region of the eye orbit is known as the lacrimal gland. Its secrecy lubricates the eye’s surface, washes dust particles away, and kills germs.
(b) A yellow spot has the brightest vision and the most sensory cells, whereas a blind spot has no sensory cells and is the location where there is no vision.
(c) Presbyopia is an age-related vision problem. The lens loses flexibility in this condition, leading in far-sightedness.
Cataracts are particularly frequent in the elderly; the cornea becomes opaque, and eyesight is reduced to the point of blindness.
(d) The power of accommodation refers to the ability to focus the eye at various distances.
(e) The retinal image is both inverted and actual.

Question 8: What is meant by optical illusion? Give one example.
Solution 8:
The lifelike continuous movement on the screen is an optical illusion. The scanning beam of a picture frame of the TV camera moves so quickly on the viewing screen of the TV set that our eyes can’t keep up. This is an example of optical illusion.

Question 9: Where are the following located? Briefly mention the function of each:
(a) oval window
(b) Cochlea
(c) Semicircular canals
(d) Utriculus
Solution 9:
(a) The oval window is found in the centre of the ear. It aids in the vibration of the fluid in the cochlear canals.
(b) The cochlea is a part of the inner ear. It aids in the transmission of impulses from the auditory nerve to the brain.
In the inner ear, semicircular canals are found. These aid in maintaining the body’s dynamic homeostasis.
(d) The utriculus is a structure found in the inner ear. It connects the cochlea to the semi-circular canals. It also aids in maintaining the body’s static balance.

Question 10: Name the four principal tastes and the respective regions of the tongue concerned with their perception.
Solution 10:
The four principal tastes are sweet, salt, bitter and sour.

Question 11: Complete the following table by filling in the blank spaces.

Structure	Function
Yellow Spot	…………….
……………………	Transfers impulse from inner ear to brain
………………………	Helps to change the focal length of the eye lens
Spinal cord	……………..
Oval window	…………….
………………….	Dynamic equilibrium

Solution 11:

Structure	Function
Yellow Spot	Region of the brightest vision
Auditory nerve	Transfers impulse from inner ear to brain
Ciliary muscle	Helps to change the focal length of the eye lens
Spinal cord	Conducts impulses
Oval window	Sets fluid in cochlear canal into vibration
Semicircular canals	Dynamic equilibrium

Long Answer Type:

Question 1: Describe the mechanism of focusing the image of a distant object in your eye when you raise your head after reading a book.
Solution 1:
Because the book is frequently read from a short distance, the lens becomes more convex or rounded when reading. When we elevate our heads to look at something far away, the ciliary muscles relax to increase the tension on the suspensory ligament, allowing the lens to stretch. The lens’s curvature changes, causing us to focus on distant objects.

Question 2: Sometimes you remember a vivid picture of a dream you saw. What is the role of your eyes in this experience?
Solution 2: Through the eyes, the brain perceives a detailed picture of the dream. Our eyes have never seen such a vivid picture before. This is an example of a visual trick. The cerebrum of the central nervous system is in charge of dreaming. As a result, we might recall the vivid image seen in a dream from time to time.

Question 3: By closing the eyes and gently pressing them by your palms, you may see some specks of brilliant light. How do you get this sensation while there is no light entering your eyes?
Solution 3:
When we look at a bright object and then close our eyes, the light impression lasts only a few seconds. This is referred to as the persistence image or the following image. It just lasts a tenth of a second. As a result, you can see some brilliant light specks by closing your eyes and gently touching them with your palms.

Question 4: Explain the terms ‘adaptation’ and ‘accommodation’ with reference to the eye.
Solution 4:
The ability to modify eyesight in bright and dark environments is known as adaptation. The rhodopsin pigment, which has been broken down in high light, is restored when we enter a dark environment. It causes the pupil to dilate, allowing more light into the eyes. This is referred to as dark adaptation. The rhodopsin pigment, on the other hand, is bleached when we enter a bright place from a dark chamber. This narrows the pupil and decreases the amount of light that enters the eyes. This is referred to as ‘light adaption.’ The process of accommodation entails focussing the eye at various distances. A shift in the lens’ curvature is mostly responsible for this. The lens thickens as the ciliary muscles flex, allowing us to focus on a nearby object. When the ciliary muscles relax, the lens remains extended, as it should be, and we are able to focus on distant objects.

Question 5: You do not enjoy watching a movie from a very short distance from the screen in a cinema hall. Why?
Solution 5:
Our eyes are built to focus on a wide range of distances. Constantly focusing at a short distance might strain the lens focusing muscles. As a result, we do not enjoy watching a movie in a cinema theatre from a very close distance from the screen.

Question 6: Enumerate the common defects of vision, their causes and the possible methods of correcting them.
Solution 6:

Defect of vision	Cause	Corrective measure
Myopia	Lengthening of eye ball from front to back or the lens is too curved.	Using suitable concave lens
Hyperopia	Shortening of eye ball from front to back or the lens is too flat.	Using suitable convex lens
Astigmatism	Uneven curvature of the cornea	Using suitable cylindrical lenses
Presbyopia	Loss of flexibility of lens	Using suitable convex lens
Cataract	Lens turning opaque	Surgery or use of convex lens or implantation of plastic lens.
Colour blindness	Genetic defect	No control measure
Squint	Formation of cross-eye	Surgery and suitable exercise

Question 7: Name the three ear ossicles. How do they contribute in the mechanism of hearing?
Solution 7:
Malleus (hammer), Incus (anvil), and Stapes are the three ear ossicles (stirr up). The stapes, the last ear ossicle, vibrates and sends the vibration to the oval window. Because of their lever-like action, the other two ear ossicles increase the vibration of the stapes.

Question 8: What is meant by power of accommodation of the eye? Name the muscles of the eye responsible for the same …………
Solution 8:
The power of accommodation refers to the ability to focus the eye at various distances. The ciliary muscles are in charge of accommodation power.

Structured / Application / Skill Type:

Question 1: With reference to the functioning of the eye, answer the questions that follow:
(a) What is meant by power of accommodation of the eye?
(b) What is the shape of the lens during (1) near vision (2) distant vision?
(c) Name the two structure in the eye responsible for bringing about the change in the shape of the lens.
(d) Name the cells of the retina and their respective pigments which get activated (1) in the dark and (2) in the light.
Solution 1:
(a) The power of accommodation refers to the eye’s capacity to focus sharply on objects that are both close and far away.
(b) The eye’s shape:
• Flattened eyesight in close quarters
• Distant – more convex or rounded
(c) Suspensory ligament and iliary muscles
(d) In the dim light: Rod cells are a type of cell. Rhodopsin is a pigment. In the open: Cone cells are a type of cell. Iodopsin is a pigment.

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 three small bones present in the middle ear. What is the biological term for them collectively?
(c) Name the part of the ear associated with (1) static balance (2) hearing (3) dynamic balance.
(d) Name the nerve, which transmits messages from the ear to the brain.
Solution 2:
(a) The cochlea and semi-circular canals are two structures found within the middle ear, also known as the membranous labyrinth.
b) The malleus, incus, and stapes are the three bones that make up the malleus.
c) Static equilibrium – Sacculus and utriculus (inner ear) Internal ear hearing
Dynamic equilibrium – Canals that are semi-circular in shape (inner ear) They are referred to as ossicles collectively.

Question 3: The figure below compares a part of our eye with a part of a photographic camera.

(a) name the corresponding parts of the eye the camera shown here that are comparable in function.
(b) Explain the mode of working and the functions of the parts of the eye mentioned above
Solution 3:
(a) Cornea is similar to the camera’s lens cover. The iris and pupil function similarly to a camera’s aperture.
(b) The cornea is the primary focusing element of the eye. It bends widely diverging light beams past the pupil, which are then further converged by the lens.

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.
Solution 4:
(a) Myopia
(b) (b) Myopia can be caused by either the eyeball being too long from front to back or the lens being overly bent.
(c) 1 – vitreous humour, 2 – blind spot, 3-lens, 4-pupil
(d) Concave lens

Question 5: The figure below is the sectional view of a part of the skull showing s sense organ:

(i) Name the sense organ
(ii) What are the parts labelled ‘m’, “I” and “s”? what do these three parts constitute collectively?
(iii) what do you call the part shown in the form of a spiral? What is it function?
(iv) Name the part labelled “tm”? What is its function?
Solution 5:
(i) Ear
(ii) m – malleus, i – incus and s – stapes respectively. These are collectively called as ear ossicles.
(iii) Cochlea. Vibrations in the hair of the sense cells in the cochlea transfer the hearing impulse to the brain via the auditory nerve.
(iv) Membrane of the tympanic cavity. In the process of hearing, it vibrates and then sets the ear ossicles vibrating.

Question 6: Given below is the 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’
Solution 6:
(i) Ear ossicles
(ii) A – Cochlea, B – Semicircular canals, C – Ear ossicles
(iii) (iii) The cochlea aids in the transmission of impulses from the auditory nerve to the brain. The body’s dynamic balance is maintained via semicircular canals.
(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.
Solution 7:

Utriculus and Sacculus 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 looking glasses she needs?
Solution 8:
(a) Myopia
(b) –Normal eye, B-Myopia
(c) Looking glasses with the concave lens are required here.