Skip to content
CNMS ICSE - 7 Std
Share
Explore

Answer key

Prepared by: learnloophq@gmail.com

Chapter: 07. Nervous System

⁠

SECTION A: MULTIPLE CHOICE QUESTIONS

© Myelin sheath
(b) Sensory nerves
(b) Gray matter
(d) Cerebellum
(a) 12 pairs of cranial nerves and 31 pairs of spinal nerves
⁠

SECTION B: FILL IN THE BLANKS

neuron (or nerve cell)
synapse
gray
gyri
parasympathetic
⁠

SECTION C: TRUE OR FALSE

True
True
False (Correction: In the spinal cord, the arrangement of gray and white matter is the reverse of the brain.)
True
False (Correction: Sensory neurons conduct sensory impulses to the CNS, while motor neurons conduct motor impulses to muscles/glands.)
⁠

SECTION D: EXPLAIN THE TERMS

Stimulus: Any change or information received by the nervous system about conditions in the environment, either inside or outside the body, that evokes a reaction.
Synapse: The point of contact between the terminal branches of the axon of one neuron and the dendrites of an adjacent neuron, through which nerve impulses pass as a chemical message.
Reflex Action: An action that occurs automatically and rapidly in response to a stimulus, independent of an individual’s conscious will.
Meninges: Three protective membranes that surround and protect the brain.
⁠

SECTION E: DIFFERENTIATE THE CONCEPTS

1. Cerebrum vs. Cerebellum (Functions):
Cerebrum: It is the seat of intelligence, consciousness, and willpower. It controls reasoning, learning, memory, emotions, and interprets sensory perceptions (sight, hearing, smell, touch, etc.).
Cerebellum: Coordinates voluntary movements, controls the activities of voluntary muscles, and maintains body balance during active tasks (walking, running, swimming, etc.).
2. Sensory Nerves vs. Motor Nerves (Impulse Direction):
Sensory Nerves: Composed of sensory nerve fibres that bring impulses from the sense organs/receptors to the brain or spinal cord.
Motor Nerves: Composed of motor nerve fibres that carry impulses (orders) away from the brain or spinal cord to the effector organs (muscles or glands).
3. Gray Matter vs. White Matter in the Brain:
Gray Matter: Composed mainly of cell bodies (cytons) of neurons. In the brain, it forms the outer layer.
White Matter: Composed of axons that join to form nerves. In the brain, it forms the inner layer.
⁠

SECTION F: SHORT ANSWER QUESTIONS

The three main parts of a neuron are:
Cell body (Cyton)
Dendrons (with dendrites)
Axon ​Description of the axon: The axon is the longest single extension from the cyton. Its end divides into terminal branches that end in synaptic knobs, and in most neurons, it is insulated by a myelin sheath to speed up impulse conduction.
The medulla oblongata is called the brain stem and is vital because it coordinates all involuntary activities of internal (visceral) organs, such as breathing movements, heartbeats, swallowing, and peristalsis. An injury to the medulla is fatal because it can immediately stop these vital life-support functions, resulting in death.
Nervous System: Exercises neural control. It communicates rapidly using electrochemical impulses sent along networks of neurons and nerve fibres, providing the fastest means of communication.
Endocrine System: Exercises chemical control. It uses chemical messengers called hormones that are transported through bodily fluids to coordinate slower, long-term body activities.
When light acts as a stimulus: (a) Coordinator: Brain (Central Nervous System) (b) Effector: Eye muscles (muscles of the pupil)
⁠

SECTION G: DIAGRAM-BASED QUESTIONS

(a) Labels:
A: Dendrites / Dendron
B: Nucleus (inside the Cyton / Cell body)
C: Axon
D: Synaptic knobs (or terminal branches/knobs)
(b) Function of Part A (Dendrites): They connect a neuron with neighbouring neurons, receive nerve impulses from preceding neurons or receptors, and conduct them towards the cell body (cyton) in an afferent process.
© Function and features of the sheath around Part C (Axon): The sheath is called the myelin sheath. It insulates the axon and speeds up the conduction of nerve impulses. The regular constrictions along its length are called Nodes of Ranvier.
⁠

SECTION H: LONG ANSWER QUESTIONS

The Human Central Nervous System (CNS) consists of two main parts:
The Brain: It is the primary controlling centre. It is protected inside a bony brain case (the cranium/skull) and is additionally wrapped and protected by three membranes called the meninges.
The Spinal Cord: It is the extension of the brain stem (medulla oblongata) that runs down the back. It is securely housed and protected from injury within the neural canal of the bony vertebral column (spine).
The mechanism of nervous coordination occurs through the following sequential steps:
Receiving the Stimulus: Receptors (sensory cells) detect changes in the external or internal environment.
Processing of Stimulus (Transduction): Receptors convert the detected stimulus into electrical signals called nerve impulses.
Transmission of Nerve Impulse: The sensory impulses are transmitted via sensory nerves to the brain or spinal cord.
Interpretation: The interneurons in the central nervous system interpret these sensory impulses and convert them into motor instructions.
Transferring the Response: Motor nerve fibres carry the resulting motor instructions/impulses from the brain or spinal cord to the effectors (muscles or glands), which act according to the instructions to produce the final body response.
Gallery
 
Want to print your doc?
This is not the way.
Try clicking the ··· in the right corner or using a keyboard shortcut (
CtrlP
) instead.