Q1. [4]
In life there are certain changes in the environment called 'stimuli' to which we respond appropriately. Touching a flame suddenly is a dangerous situation for us. One way is to think consciously about the possibility of burning and then moving the hand. But our body has been designed in such a way that we save ourself from such situations immediately.
Read the source and answer the questions that follow.
- (i) Name the action by which we protect ourself in the situation mentioned above and define it. [1]
- (ii) Write the role of (a) motor and (b) relay neuron. [1]
- (iii) What are the two types of nervous system in human body? Name the components of each of them. [2]
Previously asked in CBSE board exam
2025 31/4/1 Q38
Generated by claude-sonnet-4-6 · 2026-06-15 06:49 · grounding stimulus
Model Answer
(i) The action is called Reflex Action. It is a spontaneous, automatic, and involuntary response to a stimulus that occurs without conscious thinking.
(ii)
- (a) Motor neuron: Carries impulse from the spinal cord/brain to the effector (muscle or gland).
- (b) Relay neuron: Connects the sensory neuron to the motor neuron within the spinal cord.
(iii) The two types of nervous system are:
- Central Nervous System (CNS) — Components: Brain and Spinal Cord.
- Peripheral Nervous System (PNS) — Components: Cranial nerves (arising from brain) and Spinal nerves (arising from spinal cord).
Source: Chapter – Control and Coordination, Nervous System
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Explanation
- (i) Examiners expect both the name and a one-line definition for 1 mark.
- (ii) Many students confuse motor and relay neurons — remember: relay connects, motor acts.
- (iii) A common mistake is listing only CNS. Always name both systems and their components separately. Each system with components earns 1 mark each.
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