Worksheet Solutions: Nervous System | Biology Class 7 ICSE PDF Download

Part A: Multiple Choice Questions (MCQs)

Q1. The structural and functional unit of the nervous system is:
a) Brain
b) Neuron
c) Nerve
d) Spinal cord

Answer: (b) Neuron
Explanation: Neurons are the basic units of the nervous system. They carry messages in the form of electrical signals.

Q2. Which part of the brain controls body balance and muscle coordination?
a) Cerebrum
b) Cerebellum
c) Medulla oblongata
d) Spinal cord

Answer: (b) Cerebellum
Explanation: The cerebellum manages body balance and coordinates muscular activity.

Q3. Which type of nerve carries messages from the brain to the muscles?
a) Sensory nerve
b) Motor nerve
c) Mixed nerve
d) Cranial nerve

Answer: (b) Motor nerve
Explanation: Motor nerves carry instructions from the brain and spinal cord to muscles and glands.

Q4. Which of these is an example of chemical coordination?
a) Reflex action
b) Heartbeat control by medulla
c) Hormone release during fear
d) Balancing by cerebellum

Answer: (c) Hormone release during fear
Explanation: Chemical coordination works through hormones. For example, adrenaline is secreted in stressful situations to give quick energy.

Q5. The medulla oblongata controls:
a) Memory and learning
b) Breathing and heartbeat
c) Balance of the body
d) Voluntary movements

Answer: (b) Breathing and heartbeat
Explanation: The medulla regulates involuntary actions such as heartbeat, breathing, and digestion.

Part B: Short Answer Questions

Q6. What is coordination? Why is it important?
Answer:
Coordination is the working together of different body organs and systems in a proper way.
It is important because it ensures that processes like digestion, respiration, and movement happen smoothly and the body responds effectively to changes.

Q7. What are the two main types of coordination in humans?
Answer:

1. Nervous coordination – controlled by the brain, spinal cord, nerves, and sense organs. It enables quick actions.

2. Chemical coordination – controlled by hormones. It regulates slower but long-lasting functions such as growth and emergency responses.

Q8. Write the main parts of a neuron and their functions.
Answer:

• Cyton: The cell body that contains the nucleus and controls cell activity.

• Dendrites: Receive messages from other neurons or organs.

• Axon: Carries messages away from the cell body.

• Terminal branches: Transmit messages to the next neuron at synapses.

Q9. Differentiate between sensory and motor neurons.
Answer:

• Sensory neurons: Carry impulses from sense organs (like eyes, ears, skin) to the brain or spinal cord.

• Motor neurons: Carry impulses from the brain or spinal cord to muscles or glands.

Q10. What is the role of the spinal cord?
Answer:

• It controls reflex actions below the neck.

• It carries sensory messages from skin and muscles to the brain.

• It sends commands from the brain to the muscles of the trunk and limbs.

Part C: Long Answer Questions 

Q11. Describe the structure and functions of the human brain.
Answer:
The brain is the control centre of the nervous system.

Structure:

• Protected by the skull and three coverings called meninges.

• Surrounded by cerebrospinal fluid for protection.

• Divided into three parts: cerebrum, cerebellum, and medulla oblongata.

Functions:

1. Cerebrum:

   • Largest part.

   • Controls intelligence, memory, willpower, learning, and voluntary actions like speaking or writing.

2. Cerebellum:

   • Controls body balance and coordinates muscular activity.

   • It ensures smooth and accurate movements.

3. Medulla oblongata:

   • Connects the brain to the spinal cord.

   • Controls involuntary activities such as heartbeat, breathing, digestion, and swallowing.

Q12. Explain the difference between the somatic and autonomic nervous systems.
Answer:

Somatic Nervous System:

• Made up of cranial and spinal nerves.

• Transmits sensory information (like taste, smell, sound) to the brain.

• Controls voluntary actions such as walking, writing, or lifting.

Autonomic Nervous System:

• Made of chains of ganglia and nerves along the spinal cord.

• Controls involuntary actions such as heartbeat, blood pressure, digestion, and breathing.

• Has two parts:

  • Sympathetic system: prepares the body for stress (“fight or flight”).

  • Parasympathetic system: restores normal conditions.

Q13. What is a reflex action? Explain with an example and its pathway.
Answer:

Reflex action is an automatic, quick response to a stimulus without the involvement of the brain.

Example: Pulling your hand away immediately after touching a hot object.

Pathway of Reflex Action:

1. Heat is detected by sensory receptors in the skin.

2. A sensory neuron carries the message to the spinal cord.

3. The spinal cord processes the message and sends back a command.

4. A motor neuron carries the command to the muscles.

5. Muscles contract and the hand is withdrawn.

This protects the body from injury by providing an immediate response.