Question 8
Give two examples of reflex actions.
Two examples of reflex actions are:
- Blinking of eyes when a foreign particle enters the eye.
- Immediate withdrawal of hand if you unknowingly touch a hot object.
Key Concepts Covered
This question tests your understanding of the following concepts from the chapter Nervous System in Humans: Question, Reflex, Actions, Nervous System in Humans, Biology. These are fundamental topics in Biology that students are expected to master as part of the ICSE Class 8 curriculum.
A thorough understanding of these concepts will help you answer similar questions confidently in your ICSE examinations. These topics are frequently tested in both objective and subjective sections of Biology papers. We recommend revising the relevant section of your textbook alongside practising these solved examples to build a strong foundation.
How to Approach This Question
Read the question carefully and identify what is being asked. Break down complex questions into smaller parts. Use the terminology and concepts discussed in this chapter. Structure your answer logically — begin with a definition or key statement, then provide supporting details. Review your answer to ensure it addresses all parts of the question completely.
Key Points to Remember
- Use precise scientific terminology as defined in the textbook.
- Draw and label diagrams neatly for full marks.
- Understand the difference between structure and function.
- Learn processes step-by-step in the correct sequence.
Practice more questions from Nervous System in Humans — Biology, Class 8 ICSE
Nervous System – Interactive Study Guide
The nervous system controls and coordinates all body activities through electrical impulses. It consists of the CNS (brain + spinal cord) and PNS (nerves connecting CNS to body).
Neuron – Quick Structure
- Cell body: Nucleus, metabolic centre
- Dendrites: Receive impulses (towards cell body)
- Axon: Carries impulses away (from cell body)
- Myelin sheath: Insulation, speeds up impulse
- Synaptic knob: Transmits to next neuron
Brain Parts – Quick Reference
| Part | Function | Memory Aid |
|---|---|---|
| Cerebrum | Thinking, memory, senses, voluntary actions | BRainpower |
| Cerebellum | Balance, coordination | BaLLance |
| Medulla | Involuntary actions (breathing, heartbeat) | Must Do |
Reflex Action – Step by Step
Stimulus → Receptor (skin) → Sensory neuron → Spinal cord (relay neuron) → Motor neuron → Effector (muscle) → Response (hand pulls away)
Controlled by spinal cord (NOT brain) for faster response.
Voluntary vs Involuntary vs Reflex
| Voluntary | Involuntary | Reflex | |
|---|---|---|---|
| Control | Conscious | Unconscious | Unconscious |
| Centre | Cerebrum | Medulla | Spinal cord |
| Speed | Slow | Moderate | Very fast |
| Example | Writing | Breathing | Knee-jerk |
Self-Test Questions
- Draw and label a neuron.
- Why are reflex actions controlled by the spinal cord and not the brain?
- Name the three parts of the brain and state one function of each.
- What is the difference between sensory and motor neurons?
- Draw a reflex arc and label all parts.