Human Body : The Nervous System
Exercise
SECTION I
A. Name the following.
1. Part of the neuron that receives stimulus from another neuron and transmits it as impulse to the cyton.
= Dendrites;
2. Membranous covering of brain.
= Meninges;
3. Reflex centre of the body.
= Brain;
4. Part of brain that appears like a walnut.
= Cerebrum;
5. The opaque, white, tough fibrous protective coat of eye.
= Sclera;
6. Collective terms for the three bones that make up the middle ear.
= Ear Ossicles;
7. Sense organ that is also a part of the respiratory system.
= Nose;
B. Choose the correct option.
1. Which of the following is responsible for controlling heartbeat?
a. Cerebrum. [ ]
b. Medulla. [✓]
c. Cranial nerve. [ ]
d. Cerebellum. [ ]
2. The chemical present in synaptic bulb is
a. enzyme. [ ]
b. neurotransmitter. [✓]
c. hormone. [ ]
d. cerebrospinal fluid. [ ]
3. Which of the following co-ordinates muscle activity?
a. Cerebrum. [ ]
b. Cerebellum. [✓]
c. Medulla. [ ]
d. Spinal cord. [ ]
4. Electrical signals sent by nerve cells to different parts of the body are called
a. reflex action. [ ]
b. message. [ ]
c. impulse. [✓]
d. reflex arc. [ ]
5. A long projection of nerve cell arising from cyton is called
a. dendron. [ ]
b. dendrite. [ ]
c. axon. [✓]
d. neuron. [ ]
C. Write true or false. Correct the false statements by last words only.
1. Reflex action is controlled by brain. [F]
= Reflex action is controlled by spinal cord.
2. Cell bodies of neurons are called white matters. [F]
= Cell bodies of neurons are called cyton.
3. Motor neuron transmits message from brain to sense organs. [T]
4. Cerebrum is the seat for functions such as intelligence and memory. [T]
5. Rods are sensitive to bright light. [T]
D. Match the terms in Column A with that which is most appropriate in Column B.
=
|
Column A |
Column B |
|---|---|
|
1. Cerebrum |
a. Internal involuntary action. [5] |
|
2. Nerve cell |
b. Reflex action. [4] |
|
3. Cerebellum |
c. Body balance. [3] |
|
4. Spinal Cord |
d. Voluntary actions. [1] |
|
5. Medulla |
e. Osmoregulation. [ ] |
|
|
f. Transmission of impulses. [2] |
|
|
g. Regulates body temperature. [ ] |
E. Choose the odd one out and give reasons for your choice.
1. axon, gray matter, dendrite, nucleus.
= Odd - Gray matter, it is the part of brain. The others are parts of neuron.
2. Skin, eye, kidney, nose.
= Odd - Kidney, it is excretory organ. The others are sense organs.
3. Cornea, retina, sclera, choroid.
= Odd - Cornea, it is part of sclera. The other are layers of eye.
4. Hammer, anvil, pinna, stirrup.
= Odd - Pinna, it is the part of outer ear. The others are the parts of middle ear.
F. State the exact location of the following.
1. Cerebrum.
= The cerebrum is the largest part of the brain and appears like a walnut.
2. Meninges.
= The bony skull and three membranous coverings called meninges protect the brain.
3. Spinal cord.
= The spinal cord is a cylindrical structure located inside the vertebral column.
4. Eustachian tube.
= A tube called eustachian tube filled with air connects the middle ear to the throat.
5. Melanin.
= The dark pigment melanin, which determines the skin colour, is produced in the epidermis. It is the outer tough, dead layer of skin that wears away at surface and is constantly replaced by new cells.
SECTION II
G. Explain the following terms.
1. Nervous system.
= The nervous system is a control system responsible for sending electrical signals called nerve impulses throughout our body.
2. Neuron.
= A neuron is the structural and functional unit of the nervous system.
3. Spinal nerves.
= The spinal cord is made up of thirty one segments. Each segment gives out a pair of spinal nerves.
4. Internal ear.
= The internal ear is a fluid-filled area consisting of three parts: the cochlea, semi-circular canals, and vestibule.
5. Taste bud.
= Tongue has receptors for taste called taste buds.
H. Differentiate between the following on the basis of what is given in the bracket.
1. Response and stimulus. (example)
= Example of response is muscle contract.
Example of stimulus is heat.
2. Brain and Spinal cord. (location)
= Brain is located inside the skull in the head. Spinal cord is located inside the vertebral column.
3. Cerebrum and Cerebellum. (function)
= Cerebrum controls many functions, such as voluntary actions, intelligence, memory, reasoning, planning, problem solving, emotion, and perception of sensory impulse.
Cerebellum helps to maintain body balance and it co-ordinates muscular activity.
4. Sensory neuron and motor neuron. (definition)
= Sensory neurons receive messages from sensory organs and transmit them to the brain or spinal cord for processing.
Motor neurons transmit neuron and motor neurons, and conducts impulses between them. They are found only in central nervous system.
5. Outer ear and middle ear. (parts)
= Outer ear is made up of - pinna, auditory canal, and tympanum.
Middle ear is made up of - malleus (hammer), incus (anvil), and stapes (stirrup).
I. Give reasons for the following.
1. Brain is the control centre of body.
= Brain is the control centre of body because it controls most of the voluntary and involuntary activities of human body.
2. Injury to medulla can cause death.
= Injury to medulla can cause death because it is responsible for controlling involuntary actions of internal organs, such as breathing, heartbeat, and movement of food along the alimentary canal.
3. A drunk person walk clumsily.
= A drunk person walk clumsily because his cerebellum is affected by the alcohol.
4. We suddenly move our hands after touching a hot iron.
= We suddenly move our hands after touching a hot iron due to the natural reflex action.
5. It is harmful to use a sharp object for cleaning the ear.
= It is harmful to use a sharp object for cleaning the ear because the eardrum or the tympanum can be easily affected by the sharp object.
J. Short answer questions.
1. Name the parts of a neuron.
= The parts of a neuron are - cyton and axon.
2. How is brain protected?
= Brain is protected by the bony skull and three membranous coverings called meninges.
3. Name the structures connecting the two cerebral hemisphere and the two cerebellar hemispheres.
= The structures connecting the two cerebral hemisphere and the two cerebellar hemispheres is longitudinal fissure. A sheet of fibre connects these hemispheres internally so that information can be transformed from one hemisphere to the other.
4. What is the arrangement of nerve cells in the cerebrum?
= Internally, the cerebral hemisphere is divided into an outer cortex and an inner medulla. The cortex is gray in colour containing cell bodies of neurons. It is called gray matter. The inner part consists of white matter, which contains axons of neurons.
5. What is the function of spinal cord?
= The spinal cord transmits nerve impulses from different organs in the body to the brain and vice versa. It also controls reflex actions.
6. Name the layers of human eye.
= The layers of human eye are - Sclera, Choroid and Retina.
K. Long answer questions.
1. Define a neurone and explain the three different kinds of neurons.
= A neuron is the structural and functional unit of the nervous system. It is made up of the cell body called cyton and an elongated projection called axon.
Neurons are classified into three types based on their function: Sensory neurons, motor neurons, and interneurons.
Sensory Neurons : These neurons receive messages from sensory organs and transmit them to the brain or spinal cord to muscles or glands for response to be initiated.
Interneuron : These neurons connect sensory neuron and motor neurons, and conducts impulses between them. They are found only in central nervous system.
2. With the help of labelled diagram, describe the structure of neuron.
= A neuron is a structural and functional unit of the nervous system. It is made up of the cell body called cyton and an elongated projection called axon. The cell body consists of cytoplasm and the nucleus. It gives out branched cytoplasmic projections called dendrites for receiving stimulus and transmitting nerve impulse to the cyton.
Structure of Neuron
The axon is the conducting unit of the neuron arising form the cell body. A protective fatty covering called the myelin sheath envelops the long axons. It provides insulation to the axon. The axons transmit nerve impulses away from the cell body. The distal end of axon is branched into axon terminals that end in a bulb-like structure called synaptic bulb. The synaptic bulb contains neurochemicals called neurotransmitters. The junction between two neurons, i.e., between dendrite of one neuron and the axon terminal of the immediately next neuron, is called a synapse.
3. What are the three major parts of the brain? Write an account on them.
= The human brain is divided into three main parts : the cerebrum, the cerebellum, and the medulla oblongata.
Cerebrum : The cerebrum is the largest part of the brain and appears like a walnut. The outer surface of the cerebrum is wrinkled having ridges and furrows. These wrinkles increase the surface area for accommodating a large number of neurons. Externally, the cerebrum is divided into two hemisphere by a longitudinal fissure: the right and left hemispheres. A sheet of fibre connects these hemispheres internally so that information can be transferred from one hemisphere to the other.
Internally, the cerebral hemisphere is divided into an outer cortex and an inner medulla. The cortex is gray in colour containing cell bodies of neurons. It is called gray matter. The inner part consists of white matter, which contains axons of neurons.
The cerebrum is the seat of many functions, such as voluntary actions, intelligence, memory, reasoning, planning, problem solving, emotion, and perception of sensory impulse.
Cerebellum : It is smaller is size and is located under the cerebrum at the back of the head. It is made up of two cerebellar hemispheres. These two hemispheres are joined together by pons, which forms a bridge below it. The pons carries impulses from one hemisphere of the cerebellum to another.
The cerebellum helps to maintain body balance and it co-ordinates muscular activity. The impulse for these movements is generated in the cerebrum. An alcoholic person walks clumsily losing his co-ordination and body balance because his cerebellum is affected by the alcohol.
Medulla oblongata ; The medulla oblongata is located at the posterior end of the brain and is continuous with the spinal cord.
The medulla oblongata is responsible for controlling involuntary actions of internal organs, such as breathing, heartbeat, and movement of food along the alimentary canal.
4. Draw a labelled diagram of the structure of the eye.
=
Structure of Eye
5. Explain the working of the inner ear.
= The inner ear is a fluid-filled area consisting of three parts: the cochlea, semi-circular canals, and vestibule. The cochlea is spiral-shaped and bears thousands of hair cells. It also contains sound receptors that are attached to auditory nerves. There are three semi-circular canals placed at right angles to each other and attached to the nerves within the inner ear. The end of each canal is swollen and contains sensory cells of maintaining body balance is called dynamic balance. The vestibule, which joins the semi-circular canals with the cochlea, contains sensory cells for static balance, i.e., balance of the body when it is at rest.
PICTURE SYUDY
1.
a. Identify the organ shown in the picture above. What is its function?
= The organ shown in the picture above is - Brain.
Brain controls almost all the voluntary and involuntary activities of human body.
b. Label the pointers marked as 1,2, and 3.
= 1 - Cerebrum;
2 - Cerebellum;
3 - Medulla oblongata;
c. Which of the parts controls sight, speech, memory, and thought?
= 1 - Cerebrum controls sight, speech, memory, and thought.
d. Which of these parts is located just above the spinal cord? What is its function?
= 3 - Medulla oblongata is located just above the spinal cord.
The medulla oblongata is responsible for controlling involuntary actions of internal organs, such as breathing, heartbeat, and movement of food along the alimentary canal.
2. Given below is the diagram of the human ear. Study the same and answer the following questions.
a. State the functions of the ear.
= Ears respond to stimuli created by sound waves. They are also responsible for maintaining body balance.
b. Name the parts labelled 1 -7 in the figure above.
= 1 - Pinna;
2 - Auditory canal;
3 - Tympanum;
4 - Semi circular canals;
5 - Cochlear nerve;
6 - Cochlea;
7 - Stapes;
c. Give the number and name of the part that:
i. contains receptors for hearing.
= 4 - Semi circular canals;
ii. collects sound waves from the external environment.
= 1 - Pinna;
2 - Auditory canals;
iii. provide surface for vibration of sound waves.
= 3 - Eardrum or tympanum;
iv. carries impulse to the brain for the interpretation of sound.
= 5 - Cochlear nerve;
d. State the function of parts labelled 2 and 4.
= Function of part labelled 2 - Collects sound waves from the external environment.
Function of parts labelled 4 - Transmit sound waves to cochlea.
3. Study the figure below and answer the questions that follow.
a. Label the neurons numbered 1,2, and 3 in the figure. Give reasons for your answer.
= 1 - Activation of sensory neuron. It brings the sensation of the stimuli.
2 - Information processed in the spinal cord and interneuron relays signal to motor neuron.
3 - Effector. It effects the organ of the sensation according to the level of the stimuli.
b. Name the part in the figure that is represented by:
i. receptor.
= Skin;
ii. effector.
= Muscle;
iii. stimulus.
= Heat of the candle;
c. Which process is being depicted in the figure? Define the process.
= Reflex action is being depicted in the figure.
An automatic, quick, and sudden response to a sensory stimulus, which is controlled by the spinal cord, is called reflex action.