Class 10 Science Chapter 6 — Control and Coordination (International Edition)

NCERT / RBSE Syllabus 2026–27 · Learn by doing · Includes five labelled diagrams

Author: Surendra Singh Chouhan — former Education Officer, Rajasthan. 34 years (1991–2025) in teaching, training and administration.
Based on: NCERT Class 10 Science textbook and the Board of Secondary Education, Rajasthan syllabus 2026–27.
Prepared: Compiled from the textbook, organised with AI assistance, reviewed by the author. All diagrams are original.

Touch a hot pan and your hand jerks back — before you even think about it. The thought "ouch, that's hot!" comes a moment later.

So who gave the order? And how does a touch-me-not plant, which has no brain and no nerves at all, fold its leaves the instant you touch it?

How to read this — first you think or try it, then comes the explanation:
🔍 Wonder · 🧪 Try it · 📖 Understand · 🔗 Apply · ✅ Check yourself
"Check yourself" has three levels — 1, 2, 3.

Contents — Foundation check · 1. Why coordination · 2. How nerve tissue acts · 3. Reflex action · 4. Human brain and tissue protection · 5. Immediate response in plants · 6. Growth-based movement in plants · 7. Hormones in animals · Your ladder · How to draw the diagrams · Marking scheme · Common mistakes · Final test · Glossary · For parents and teachers · Further reading

Foundation check

1. What is a tissue? (Class 9)
2. What are the life processes? (Chapter 5)
3. Are enzymes and hormones the same thing?

Answers

1. A group of cells similar in structure and function. 2. Nutrition, respiration, transportation, excretion. 3. No. Enzymes speed up a reaction; hormones are messengers that travel from one organ and instruct another. This chapter will make the difference clear.

1. Why control and coordination

🔍 Wonder — While running, your legs, arms, lungs and heart all work in rhythm. Who is coordinating all of them together?

🧪 Try it — Close your eyes and try touching your nose with one finger. Did it work? Now think — your eyes were shut, so how did the finger know the way?

Answer — Internal receptors constantly report where each body part is; the brain combines this information and controls the movement — that is coordination.

📖 Understand — Living things respond to changes in the environment — stimuli. Organising these responses systematically is control and coordination. In animals this is done by the nervous system and the endocrine system; plants have no nervous system, so their work runs on chemical signals.

🔗 Apply — A plant also responds, but slowly; an animal responds instantly, because animals have a nervous system that runs on electrical impulses.

✅ Check yourself

Level 1 What is a stimulus? — Answer: A change in the environment to which an organism responds.
Level 2 Which two systems coordinate activity in animals? — Answer: The nervous system and the endocrine (hormonal) system.
Level 3 Why is a plant's response slower than an animal's? — Answer: Plants have no nervous system. Their response depends on chemical signals and changes in water content or growth in cells — all far slower than an electrical impulse.

2. How nerve tissue acts

🔍 Wonder — A thorn pricking your toe reaches the brain in an instant — over a metre away. Which route does it take?

🧪 Try it — Ask a friend to touch your back with two pencil tips at once — sometimes close together, sometimes far apart. Without looking, say whether it was one point or two. Now try the same on your palm.

What did you notice? On the palm you can tell two very close points apart; on the back you often cannot. The reason — the palm has far more densely packed receptors. Where more information is needed, there are more receptors.

Figure 1 — A neuron. The red dot is the impulse: dendrite → cell body → axon → synapse.

📖 Understand — Cells that receive information are called receptors, usually found in sense organs. The information they collect travels as an electrical impulse.

The impulse travels from the dendrite through the cell body to the tip of the axon. There it does not touch the next cell directly — there is a fine gap called the synapse. Here the impulse releases a chemical, which crosses over and generates a fresh electrical impulse in the next cell.

This is exactly why the impulse travels in one direction only — the chemical is released only from the tip of the axon, never from the other side. This is a favourite board-exam question.

🔗 Apply — Eventually the impulse reaches a muscle cell and instructs it to contract — that is how movement happens.

✅ Check yourself

Level 1 What is the gap between two nerve cells called? — Answer: Synapse.
Level 2 How does the impulse cross the synapse? — Answer: Chemicals are released from the tip of the axon, cross the gap, and generate a new electrical impulse in the dendrite of the next cell.
Level 3 Why can a nerve impulse not travel in the reverse direction? — Answer: The chemicals are released only from the axon's tip, and the receiving sites are only on the next cell's dendrite. Neither release nor reception happens in reverse — the pathway is strictly one-way.

3. Reflex action and the reflex arc

🔍 Wonder — Hooke's question: who gave the order to pull the hand away, when the thinking happened afterward?

🧪 Try it — Cross one leg over the other on a chair and gently tap the edge of your palm just below the raised knee. Guess first — what will happen, and can you stop it?

What happened? The leg kicks up on its own, and you cannot stop it even if you try. This is a reflex action — your will has no part in it.