Nervous System

Selina Concise Biology Class 7 ICSE Solutions – Nervous System

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Selina Concise Biology Class 7 ICSE Solutions – Nervous System

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Selina Concise ICSE Solutions for Class 7 Biology Chapter 6 Nervous System

Synopsis —

  • The interaction of these activities of a living being as per the needs of the body internally or externally is called coordination.
  • Nervous coordination is brought about by the nervous system which is made up of the brain, spinal cord, nerves and the sense organs.
  • Chemical coordination is brought about through chemical messengers called hormones.
  • The nervous system is made up of special cells called nerve cells or neurons.
  • The end of the axon terminates in a number of branches called terminal branches.
  • The terminal branches of the axon of one neuron lie very close to the dendrites of another neuron. This point of contact is called a synapse.
  • A nerve is formed of a bundle of axons (nerve fibres) enclosed in a tubular medullary sheath. There are three kind of nerves as describe
    1. sensory nerve
    2. motor nerve
    3. mixed nerve.
  • The nervous sytem of human beings consists of the following three systems:
    1. The central nervous system
    2. The peripheral nervous system
    3. The autonomic nervous system
  • The brain has three main parts:
    1. The cerebrum
    2. The cerebellum, and
    3. The medulla oblongata
  • The main functions of the spinal cord are:
    1. To control reflexes below the neck.
    2. To conduct messages from the skin and muscles to the brain.
    3. To conduct commands from the brain to muscles of the trunk and limbs.
  • The autonomic nervous system consists of a pair of chain of nerves and ganglia found on either side of the backbone.  This system controls the involuntary activities of the internal organs.
  • Stimulus: Any change in the environment that usually results in change in the activity of the body.
  • Response: The activity of the body in response to a received stimulus.
  • Impulse: A wave of electrical disturbance that runs through the nerves.
  • Receptors : These are sense organs which receives the stimulus.
  • Effector: Any muscle or gland where the response occurs.

Review Questions

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) Medulla oblongata controls
(i) Smelling
(ii) Beating of heart and respiratory movement
(iii) Intelligence and will power
(iv) Balancing the body

(b) Spinal cord is an extention of:
(i) Cerebellum
(ii) Cerebrum
(iii) Vertebral column
(iv) Medulla oblongata

(c) Body posture is mantained by:
(i) Cerebellum
(ii) Cerebrum
(iii) Medulla oblongata
(iv) Spinal cord

Short Answer Questions:

1. Write one word in the space provided to complete the second pair of the related words pertaining to nervous system.
Memory: cerebrum:: breathing:
Balance: cerebellum:: reasoning:
Answer:
Memory: cerebrum: beathing: medulla oblongata
Balance: cerebellum:: reasoning: cerebrum

2. (a) Name three major divisions of the human nervous system.
Answer:

  1. The central nervous system (brain and spinal cord)
  2. The peripheral nervous system
  3. The autonomic nervous system

(b) Name the three main parts of human brain.
Answer:

  1. Cerebrum
  2. Cerebellum
  3. Medulla oblongata

3. Given here is the diagram of a neuron. Name the parts numbered 1-6.
Selina Concise Biology Class 7 ICSE Solutions - Nervous System 1

Answer:

  1. dendrite
  2. dendrite (Terminal Arborization)
  3. nucleus
  4. axon (Nerve fibre)
  5. cell Body (cyton)
  6. node of ranvier
  7. sheath

Long answer questions

Question 1.
With the help of a suitable diagram describe the structure of a neuron.
Answer:
Selina Concise Biology Class 7 ICSE Solutions - Nervous System 2

Nervous system consists of special cells called nerve cells or neurons. It has a main cell body called cyton. It gives out many processes called dendrites. From it a very long process is given out. It is called axon or nerve fibre.

The cell body has a nucleus. The dendrites get the message from the organs and send this message to the axon through the cell body. Then the axon sends the message to muscles to contrast or to the gland for secretion.

The neurons make contact with one another through their processes. The axon at its end branches and meets the dendrites of another neuron. The meeting point is called synapse. The message is passed on from one axon to the dendrites of another neuron. How the message goes ? It is like this:
Organ → Message goes to dendrites →Cell body → Axon → Muscles or  glands

Question 2.
Briefly describe the structure of the cerebrum in human brain, and mention its functions.
Answer:
Brain consists of main three parts and lies in the cranial cavity of skull.

  1. The cerebrum
  2. The cerebellum
  3. The medulla oblongata

Cerebrum — It is very large and form two third of the whole brain. The two hemispheres are separated from each other by a deep longitudinal groove, the median fissure. The outer surface is folded with ridges and grooves. The hemispheres are hollow from inside and their walls have outer and inner portions. The outer portion has cell bodies of the neurons and it is called grey matter.
The wavery edges of the folded layer has large number of neurons to the extent of nine billion. The inner portion of the cerebrum has axons and it is called white matter.
Functions:

  1. It controls all the voluntary activities.
  2. It is the seat of intelligence, consciousness and will power.

Question 3.
Mention the three functions of spinal cord.
Answer:
Spinal cord has the following functions.

  1. It is the centre of reflex actions below the neck.
  2. It carries messages from the skin and muscles to the brain.
  3. All the stimuli and responses are passed from and to the brain through the spinal cord.

Question 4.
Describe three kinds of nerves, giving example of each.
Answer:
A nerve is formed by a group of nerve fibres (axons) encased
by tubular medullary sheath. The medullary sheath acts as insulation and do not allow mixing up of impulses of the neighbouring axons (nerve fibres) We have three kinds of nerves:

  1. Sensory nerve — It brings impulses from sense organs as these have sensory fibres. These nerve carry the impulses from the sense organs to the brain or to the spinal cord as optic nerve of the eye.
  2. Motor nerves—These carry impulses to muscles or glands from the brain or spinal cord. These nerves have only motor fibres as nerves to the muscles of the eye ball.
  3. Mixed nerve — It has both sensory and motors fibres as nerve going to the tongue.

Question 5.
What are voluntary and involuntary actions ? Which part of the nervous system controls them ?
Answer:
Voluntary action: When an action is produced with the involvement of thoughts, they are called the voluntary action. For example, writing an article jumping from heights. These actions are produced consciously by our body.
Involuntary action: Actions which take place without consciousness or willingness of an individual are called the involuntary action. Digestion, heart beating, sneezing, etc are few examples of involuntary actions.

  1. The cerebral cortex controls our voluntary actions like running and walking etc.
  2. Medulla helps in involuntary actions like hearbeat, breathing etc.

Additional Questions

I. Multiple choice questions. Tick (✓) the correct choice:

I. Nervous system in humans consists of
(a) brain and nerves
(b) brain and spinal cord
(c) brain, spinal cord and nerves
(d) none of the above.

II. Fill in the blanks:

  1. Basic structural unit of the nervous system is the neuron.
  2. Central nervous system consists of brain and spinal cord.
  3. A neuron consists of cell body, dendrite and axon.
  4. The neurons carrying impulses from the brain to the muscles are called motor or efferent neurons.
  5. Peripheral nervous system consists of nerves.
  6. The three main parts of the brain are cerebrum, cerebellum and medulla oblongata (brain stem).

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

1. Each neuron consists of three parts called cell body, cyton and axon.
 False. Each neuron consists of three parts called cell body, dendrite and axon.

2. The largest part of the brain is the cerebrum.
 True.

3. Cerebellum maintains balance of the body.
True.

4. There are 31 pairs of cranial nerves.
 False. There are 12 pairs of cranial nerves.

IV. Find the odd-one out, giving reasons:
Axon, cell body, dendrite, cerebellum
Ans. Cerebellum is the odd one out as it is a part of brain while rest three are parts of a neuron.

V. Define the following:
1. Reflex arc
2. Sensory neuron
3. Motor neuron
4. Neuron
Answer:

  1. Reflex arc: The path that an impulse takes in a reflex action is called a reflex arc.
  2. Sensory neuron: The neurons which carry impulses
    from the body parts to the spinal cord or the brain are called sensory or afferent neurons. For example, optic nerve of the eye.
  3. Motor neuron: The neurons which carry impulses from the brain or spinal cord to the body parts are called motor or efferent neurons.
  4. Neuron: A neuron or a nerve cell is the basic structural and functional unit of the nervous system.

VI. Answer the following:

Question 1.
 Describe the two parts of the nervous system.
Answer:
The nervous system of human has two parts:

  1. Central Nervous System (CNS): It consists of the brain and the spinal cord. The brain lies protected inside the skull while the spinal cord is protected within the vertebral column.
  2. Peripheral Nervous System (PNS): It consists of nerves arising from the spinal cord (spinal nerves) and the brain (cranial nerves). These nerves link the central nervous system with the various body organs.

Question 2.
What are nerves? Mention the types of nerves found in humans.
Answer:
A bundle of nerve fibres joined together as a tubular sheath that transmits impulses between brain or spinal cord and other body parts is called a nerve. The nerves constitute the peripheral nervous system.
Nerves are of two types in humans:

  1. Cranial nerves: They emerge from the brain. There are 12 pairs of cranial nerves.
  2. Spinal nerves: They emerge from the spinal cord. There are 31 pairs of spinal nerves.

Question 3.
Explain the structure of brain.
Answer:
The brain is the main control centre of the nervous system.
It is enclosed within the bony shell of cranium.
It consists ofthree main part:

    1. Cerebrum: It is the uppermost and largest part with many ridges and grooves. It is divided into right and left halves called cerebral hemispheres. It controls our thinking, reasoning, intelligence, memory and perception of pain, sound, touch, taste and smell.
    2. Cerebellum: It is located under the cerebrum at the back of the head. It maintains balance of the body and coordinates muscular activity.
    3. Brain stem (medulla oblongata): It joins the brain to the spinal cord. It controls the activity of internal organs like heartbeat and breathing.
      Selina Concise Biology Class 7 ICSE Solutions - Nervous System 3

Question 4.
Compare the nervous system and the endocrine system.
Answer:
Nervous system

  1. Messages are sent through nerve fibres.
  2. It consists of brain, spinal cord and nerves.
  3. No hormones are secreted. Messages are sent as impulses.
  4. Transmission of impulse is quick.

Endocrine system

  1. Messages are sent through blood in the form of hormones.
  2. It consists of endocrine glands.
  3. Hormones secreted by glands regulate the body activities. .
  4. Transmission takes time.

Selina Concise Biology Class 10 ICSE Solutions The Nervous System

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Selina Concise Biology Class 10 ICSE Solutions The Nervous System

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 10 Biology Chapter 9 The Nervous System. You can download the Selina Concise Biology ICSE Solutions for Class 10 with Free PDF download option. Selina Publishers Concise Biology for Class 10 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Selina ICSE Solutions for Class 10 Biology Chapter 9 The Nervous System

Exercise 1

Solution A.1.
(b) neurolemma

Solution A.2.
(d) Pons – consciousness

Solution A.3.
(b) Contains both sensory and motor fibres

Solution B.1.
(a) Cerebrospinal fluid
(b) Synapse
(c) Cerebrum
(d) Hypothalamus

Solution B.2.
(a) Stimulus: Receptor:: Impulse: Effectors
(b) Cerebrum: Diencephalon:: Cerebellum: Medulla oblongata
(c) Receptor: Sensory nerve:: Motor nerve: Effector

Solution B.3.
(a) Sensory
(b) Maintaining posture and equilibrium
(c) Spinal cord

Solution C.1.
(a) Corpus Callosum – It is located located in the forebrain. It connects two cerebral hemispheres and transfers information from one hemisphere to other.
(b) Central canal – It is located in centre of the spinal cord. It is in continuation with the cavities of the brain. It is filled with cerebrospinal fluid and acts as shock proof cushion. In addition, it also helps in exchange of materials with neurons.

Solution C.2.
(a) False
(b) False
(c) True
(d) True

Solution C.3.
(a)

Cerebrum Cerebellum
The cerebrum controls all voluntary actions. It enables us to think, reason, plan and memorize. The cerebellum on the other hand maintains balance of the body and coordinates muscular activity.

(b)

Sympathetic Nervous System Parasympathetic Nervous System
Sympathetic nervous system prepares the body for violent action against the abnormal condition. Parasympathetic nervous system is concerned with re-establishing normal conditions after the violent act is over.

(c)

Sensory Nerve Motor Nerve
Sensory nerve brings impulses from the receptors i.e. sense organs to the brain or spinal cord.

Motor nerve carries impulse from the brain or spinal cord to effector organs such as muscles or glands.

(d)

Medulla Oblongata Cerebellum
Medulla oblongata controls the  activities of internal organs and many other involuntary actions The cerebellum on the other hand maintains balance of the body and coordinates muscular activity.

(e)

Cerebrum Spinal Cord
The grey matter containing cytons lies in the cortex (outer region) while the white matter containing axons lies in the medullary region (inner region). The grey matter containing cytons lies in the medullary region i.e. inner side while the white matter containing axons lies in the cortex i.e. the outer region.

Solution C.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.

Solution C.5.
(a) Synapse: It is a gap between the axon terminal of one neuron and the dendrites of the adjacent neuron. It transmits nerve impulse from one neuron to another neuron.
(b) Association Neuron: It interconnects sensory and motor neurons.
(c) Medullary sheath: It provides insulation and prevents mixing of impulses in the adjacent axons.
(d) Medulla Oblongata: It controls activities of internal organs such as peristalsis, breathing and many other involuntary actions.
(e) Cerebellum: It maintains balance of the body and coordinates muscular activity.
(f) Cerebrospinal Fluid: It acts like a cushion and protects the brain from shocks.

Solution C.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

Solution C.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

Solution D.1.
(a) Reflex action  is an autonomic, quick and involuntary action in the body brought about by a stimulus.
(b)

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

Solution D.2.
The advantages of having a nervous system are as follows:

  1. Keeps us informed about the outside world through sense organs.
  2. Enables us to remember, think and reason out.
  3. Controls and harmonizes all voluntary muscular activities such as running, holding, writing
  4. Regulates involuntary activities such as breathing, beating of the heart without our thinking about them.

Solution D.3.
The brain and the spinal cord lie in the skull and the vertebral column respectively. They have an important role to play because all bodily activities are controlled by them. A stimulus from any part of the body is always carried to the brain or spinal cord for the correct response. A response to a stimulus is also generated in the central nervous system. Therefore, the brain and the spinal cord are called the central nervous system.

Solution D.4.
Reflex actions are involuntary actions which occur unknowingly. Voluntary actions on the other hand are performed consciously.
Picking up an apple and eating it is an example of voluntary action whereas withdrawal of hand on touching a hot object is an example of reflex action.

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.

Solution D.5.
Selina Concise Biology Class 10 ICSE Solutions The Excretory System (Elimination of Body Wastes) image - 1

Solution D.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

Solution E.1.
Salivation is an example of conditioned reflex that develops due to experience or learning. Saliva starts pouring when you chew or eat food. Therefore, this reflex will occur not just on the sight or smell of food. The brain actually needs to remember the taste of food. Boy B started salivating because he must have tasted that food prior unlike boy A.

Solution E.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

Solution E.3.
Fill in the following information in the diagram.

  1. Central Nervous System
  2. Autonomic
  3. 12
  4. spinal
  5. 31
  6. dilates
  7. constricts
  8. liver

Exercise 2

Solution A.1.
(b) Cornea

Solution A.2.
(b) Cochlea

Solution A.3.
(c) Eustachian tube, tympanum and utriculus

Solution A.4.
(a) Retina

Solution B.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

Solution B.2.
(a) Cones: Iodopsin:: rods: rhodopsin
(b) Sound: ear drum:: dynamic balance: semi-circular canals

Solution B.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 (e) free of rod cells, (a) colour of the eye
v. Meninges (c) Protective covering of the brain

Solution C.1.
(a) Myopia results when the eye ball is lengthened from front to back or the lens is too curved.
Hyperopia results from either too shortening of the eyeball from front to back or when the lens is too flat.
(b) Rods are sensitive to dim light but do not respond to colour.
cones are sensitive to bright light and are responsible for colour vision.
(c) cochlea is responsible for hearing; it can perceive the senses of hearing.
Semicircular canals are responsible for perceiving the senses to maintain the body balance.
(d) Rod cells contain rhodopsin whereas the cone cells contain iodopsin.
(e) Dynamic balance is when the body is in motion whereas static balance is positional balance with respect to gravity.

Solution C.2.
(a) False
Correct statement: Deafness is caused due to rupturing of the eardrum.
(b) False
Correct statement: Semicircular canals are concerned with dynamic balance.

Solution C.3.
(a) Fovea centralis is located at the back of the eye almost at the centre of the eyeball. It is the region of the brightest vision and also of the colour vision.
(b) Organ of corti is located in the inner ear. It contains sensory cells which process hearing.

Solution C.4.
(a) True
(b) False/ Ciliary muscles regulate the size of the lens.
(c) True
(d) False/The auditory nerve responsible for sound as well as for the body balance.
(e) True
(f) False/ flavour is a combination of taste and smell.
(g) False/ short-sightedness is myopia and hyperopia is long-sightedness.
(h) True

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

Solution C.6.
(a) Organ of Corti and hearing
(b) Olfactory nerve and smell
(c) Retina and vision
(d) Taste bud and taste

Solution C.7.
(a) Lacrimal gland is a tear gland located at the upper sideward portion of the eye orbit. Its secreation lubricates the surface of the eye, washes aways the dust particles and kills germs
(b) Yellow spot is the region of brightest vision and contains maximum sensory cells whereas a blind spot contains no sensory cells and this is the point of no vision.
(c) Presbyopia is an age-old eye defect. In this condition, the lens loses flexibility resulting in far-sightedness.
Cataract is also very common in old people, the cornea becomes opaque and the vision is cut down even to blindness.
(d) The process of focusing the eye at different distances is called the power of accommodation.
(e) The image formed on the retina is inverted and real.

Solution C.8.
An optical illusion is the life-like continuous movement on the screen. Television is an example of optical illusion, where the scanning beam of a picture frame of the TV camera moves so rapidly on the viewing screen of the TV set that our eyes cannot keep pace with it.

Solution C.9.
(a) Oval window is located in the middle ear. It helps in setting the fluid in the cochlear canals into vibration.
(b) Cochlea is located in the inner ear. It helps in transmitting impulses to the brain via the auditory nerve.
(c) Semicircular canals are located in the inner ear. These help in maintaining the dynamic equilibrium of the body.
(d) 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.

Solution C.10.
Selina Concise Biology Class 10 ICSE Solutions The Excretory System (Elimination of Body Wastes) image - 2

Solution C.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

Solution D.1.
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.
Selina Concise Biology Class 10 ICSE Solutions The Excretory System (Elimination of Body Wastes) image - 3

Solution D.2.
The brain sees the vivid picture of the dream through the eyes. Our eyes have actually never seen the vivid picture. This is an example of optical illusion. The area of dream is controlled by the cerebrum of the central nervous system. So sometime we can remember the vivid picture seen in the dream.

Solution D.3.
If we look at a bright object and then close our eyes, the sensation of light persists for a short period. This is known as persistence image or the after image. It lasts for one-tenth of a second. Therefore by closing the eyes and gently pressing them with your palms, you see some specs of brilliant light.

Solution D.4.
Adaptation is the ability to adjust vision in bright and dark areas. When we enter a dark room from bright light, the rhodopsin pigment broken down in bright light is regenerated. It dilates the pupil and allows more light to enter the eyes. This is called dark adaptation. On the other hand, if we enter bright area from a dark room, the rhodopsin pigment is bleached. This constricts the pupil and reduces the light entering the eyes. This is called ‘light adaptation‘

Accommodation is the process of focusing the eye at different distances. This is mainly brought about by a change in the curvature of the lens. When the ciliary muscles contract, the lens becomes thicker and we are able to focus a nearby object. On the other hand when the ciliary muscles relax, the lens remains stretched i.e. the normal condition and we are able to focus on distant object.

Solution D.5.
Our eyes are designed to focus at a great variety of distances. To focus constantly at a short distance can make the lens focusing muscles fatigued. Therefore, we do not enjoy watching a movie from a very short distance from the screen in cinema hall.

Solution D.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

Solution D.7.
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.

Solution D.8.
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.

Solution E.1.
a. The ability of the eye to focus sharply on things which are near to the eye as well as far off is known as the power of accommodation.
b. Shape of the eye:
Near vision – flattened
Distant – rounded or more convex
c. Ciliary muscles and suspensory ligament
d. In the dark: Cells – rod cells, Pigment – rhodopsin
In the light: Cells – cone cells, Pigment – iodopsin

Solution E.2.
a. The middle ear or membranous labyrinth has two structures inside it, the cochlea and the semi-circular canals.
b. Malleus, incus and stapes
c. Static balance – Utriculus and sacculus (inner ear)
Hearing – Internal ear
Dynamic balance – Semi-circular canals (inner ear)
d. Collectively they are termed as ossicles.

Solution E.3.
(a) Cornea is comparable to the lens cover of the camera.
The iris and pupil act like the aperture of a camera.
(b) The cornea is the eye’s main focusing element. It takes widely diverging rays of light and bends them through the pupil; the rays are further converged by the lens.

Solution E.4.
(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) 1 – vitreous humour, 2 – blind spot, 3-lens, 4-pupil
(d) Concave lens
Selina Concise Biology Class 10 ICSE Solutions The Excretory System (Elimination of Body Wastes) image - 4

Solution E.5.
(i) Ear
(ii) m – malleus, i – incus and s – stapes respectively. 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.

Solution E.6.
(i) Ear ossicles
(ii) 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

Solution E.7.
Selina Concise Biology Class 10 ICSE Solutions The Excretory System (Elimination of Body Wastes) image - 5

Solution E.8.
(a) Myopia
(b) A-Normal eye, B-Myopia
(c) Looking glasses with the concave lens are required here.

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