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Class 10 Control and Coordination notes: NCERT Science Chapter 6 revision

CMDLearn · 3 November 2026

These are short revision notes for Chapter 6 of the NCERT Class 10 Science textbook (Reprint 2026-27). The chapter runs from page 100 to page 112 and has three parts: the nervous system in animals, how plants respond without nerves, and hormones in animals. The notes follow the book's sections, then give the key words, the diagram to practise, the mistakes students make most often and 8 quick questions of our own with answers.

Keep the textbook open next to these notes. The wording here is our own; the textbook is the authority.

How much it counts

CBSE's Class 10 Science curriculum for 2026-27 puts Control and Coordination in Unit II, World of Living, worth 25 of the 80 theory marks, together with Life Processes, How do Organisms Reproduce and Heredity (curriculum, PDF page 4). For this chapter the unit lists tropic movements and plant hormones, the nervous system, voluntary, involuntary and reflex action, and animal hormones (PDF page 5). CBSE gives marks per unit, not per chapter, so no one can honestly tell you an exact mark count for this chapter alone. More on the units: CBSE Class 10 Science syllabus 2026-27.

1. Why living things need control and coordination (chapter opening, page 100)

• Some movements come from growth (a seedling pushing up through soil). Others have nothing to do with growth (a cat running, a buffalo chewing cud).
• We link movement with life because movement is usually a response to a change in the surroundings, and the organism uses it to its advantage.
• Each kind of change calls for the right response, not just any response. That needs a system that recognises the event and picks the movement: control and coordination.
• Multicellular organisms use specialised tissues for this job.

2. The nervous system and the neuron (section 6.1, pages 100-101)

• In animals, nervous tissue and muscle tissue do the controlling and coordinating.
• Information from outside is picked up by receptors: the specialised tips of certain nerve cells, mostly in the sense organs (inner ear, nose, tongue and so on). Gustatory receptors sense taste; olfactory receptors sense smell.
• How a message travels through one neuron (Fig. 6.1 a): 1. The dendrite tip picks up the information, and a chemical reaction there makes an electrical impulse. 2. The impulse runs from the dendrite to the cell body, then along the axon to its end. 3. At the axon's end the impulse makes the neuron release chemicals. 4. The chemicals cross the small gap called the synapse and set off a fresh electrical impulse in the following neuron's dendrite.
• A similar junction passes the message from a neuron to a muscle cell or a gland (Fig. 6.1 b, the neuromuscular junction).
• So nervous tissue is an organised network of neurons that carries information as electrical impulses.

3. Reflex actions and the reflex arc (section 6.1.1, pages 102-103)

• A reflex is a sudden response to something in the surroundings that happens without our thinking about it.
• Thinking takes time, because it uses complicated networks of many neurons in the brain. For an urgent danger, waiting for the brain could mean getting hurt.
• The body's answer: connect the nerve that detects the danger to the nerve that moves the muscle directly. This connection is the reflex arc (Fig. 6.2).
• The connection is made in the spinal cord, where the body's nerves gather into one bundle before going on to the brain. The information still goes on to the brain as well.
• Fig. 6.2 labels the path: receptor in the skin → sensory neuron → relay neuron in the spinal cord → motor neuron → effector (the muscle in the arm), with a branch carrying the message to the brain.
• Many animals have little or none of the neuron network needed for thinking, so reflex arcs probably evolved to work without real thought. Even in animals that can think, they stay the fastest way to respond.

4. The human brain (section 6.1.2, pages 103-104)

• Central nervous system (CNS) = brain + spinal cord. It receives information from the whole body and puts it together.
• Peripheral nervous system = cranial nerves (from the brain) + spinal nerves (from the spinal cord). It links the CNS with the rest of the body.
• Voluntary actions (writing, talking, clapping) are decided by the brain, which then sends messages to the muscles.
• The brain has three main regions:

• Fig. 6.3 also labels the cerebrum, the cranium (skull), the hypothalamus, the pituitary gland and the pons (part of the hind-brain).
• Between quick reflexes (like the pupil changing size) and thought-out actions (like moving a chair) sits a third group: involuntary actions such as the heartbeat and the mouth watering at the sight of food, which we cannot easily control by thinking.

5. Protection, and how muscles move (sections 6.1.3 and 6.1.4, page 105)

• The brain sits in a bony box (the skull), inside a fluid-filled balloon that absorbs shocks.
• The vertebral column (backbone) protects the spinal cord.
• Muscles do the final job. Muscle cells contain special proteins that change their shape and arrangement when a nerve impulse arrives, which makes the cells shorter: that is the movement.

6. Coordination in plants (section 6.2, pages 105-108)

Plants have no nervous system and no muscles, yet they respond. They move in two ways:

• Movement without growth, which is fast: the leaves of the chhui-mui (sensitive plant, touch-me-not) fold and droop when touched (Fig. 6.4). - The movement happens away from the spot that was touched, so the message must be passed along. - Plant cells pass it by electrical-chemical means, but plants have no special conducting tissue. - Their cells take in or lose water, so they swell or shrink and change shape; no muscle proteins are involved.
• Movement due to growth, which is slow: - Tendrils (as in the pea plant) are sensitive to touch. The side touching the support grows more slowly than the side away from it, so the tendril curls round the support. - Tropic movements are growth towards or away from a stimulus. - Phototropism: shoots bend towards light, roots bend away from it. - Geotropism: roots grow down and shoots grow up, in response to gravity (Fig. 6.6). - Hydrotropism (water) and chemotropism (chemicals). The book's chemotropism example is the pollen tube growing towards the ovule.
• Speed varies: the sensitive plant responds very quickly, a sunflower following day and night is slow, and growth-related movement is slower still.

7. Why bodies also use chemicals (page 108)

Electrical impulses are fast, but they have two limits:

• they reach only the cells joined by nervous tissue, not every cell;
• a cell needs time to reset before it can fire again, so it cannot send impulses non-stop.

So most multicellular organisms also use chemical communication: a stimulated cell releases a compound that spreads around, and cells with the right detecting molecules on their surface respond. It is slower, but it can reach every cell and can go on steadily. These compounds are hormones.

8. Plant hormones (page 108)

Plant hormones are made away from where they act and diffuse to the place of action.

9. Hormones in animals (section 6.3, pages 109-111)

• Adrenaline (from the adrenal glands) prepares the body to fight or run away. It goes straight into the blood and acts on target organs, including the heart: - the heart beats faster, so muscles get more oxygen; - less blood goes to the digestive system and skin (small arteries there narrow), so more reaches the skeletal muscles; - breathing gets faster (diaphragm and rib muscles contract more).
• Hormones form the endocrine system, the body's second way of control and coordination.
• Hormones also keep growth in the right places: no one grows a finger on the face.

The hormones the chapter names (Fig. 6.7 shows where the glands are):

Fig. 6.7 also marks the pineal gland, parathyroid glands and thymus; the chapter does not describe their hormones.

• Feedback mechanism: the timing and amount of a hormone are controlled by feedback. When blood sugar rises, the pancreas detects it and makes more insulin; as the sugar falls, it makes less (page 111).

Key words at a glance

• Receptor: the tip of a nerve cell that detects a change, usually in a sense organ.
• Synapse: the gap between two neurons, crossed by chemicals.
• Reflex arc: the direct link in the spinal cord from the sensing nerve to the moving nerve.
• Effector: the muscle or gland that carries out the response.
• CNS: brain and spinal cord. PNS: cranial and spinal nerves.
• Tropism: growth towards or away from a stimulus (photo-, geo-, hydro-, chemo-).
• Hormone: a chemical messenger made in one part of the body that acts in another.
• Endocrine gland: a gland that releases its hormone directly into the blood.
• Feedback mechanism: the control that raises or lowers how much hormone is released.

The diagram to know: the reflex arc

Board papers often ask you to draw and label a reflex arc. Practise it in this order:

1. Draw a cross-section of the spinal cord at the right (a rounded shape with a darker, butterfly-shaped centre).
2. Draw an arm at the left with a receptor marked in the skin of the hand.
3. Draw the sensory neuron from the receptor into the spinal cord, with an arrow pointing towards the cord.
4. Inside the cord, draw a short relay neuron linking it to the next neuron.
5. Draw the motor neuron from the cord back to a muscle in the arm (the effector), with an arrow pointing away from the cord.
6. Add an arrow leaving the cord labelled "message to the brain".

Label all six parts and give the diagram a title. The arrows earn marks: a reflex arc with no directions is incomplete.

Mistakes that cost marks

• Saying the brain makes the reflex. The arc is made in the spinal cord; the brain is informed as well, but the quick response does not wait for it.
• Calling the synapse electrical. The impulse inside a neuron is electrical; it crosses the synapse as chemicals.
• Mixing up medulla and cerebellum. Medulla: blood pressure, salivation, vomiting. Cerebellum: precision, posture, balance.
• Saying auxin collects on the lit side. It moves to the shady side, which grows faster, so the shoot bends towards the light.
• Calling the sensitive plant's movement growth. Its leaves move by water changes in cells, with no growth.
• Calling every slow plant movement phototropism. Check the stimulus: gravity (geo-), water (hydro-), chemicals (chemo-).
• Writing that hormones travel along nerves. Animal hormones are released into the blood.

Quick check: 8 questions of our own

These are our own questions, written for these notes and checked against the textbook pages named; no practising teacher has reviewed them yet.

Question 1. While picking roses, Anu's finger is pricked by a thorn and she pulls her hand back before she even feels the pain. Put these in the order the message travels: motor neuron, receptor in the skin, relay neuron, arm muscle, sensory neuron. Where is the link between the "in" and "out" nerves made?

Answer: receptor in the skin → sensory neuron → relay neuron → motor neuron → arm muscle; the link is in the spinal cord. The arm muscle is the effector. The reflex arc is formed in the spinal cord, and the message also travels on to the brain, which is why Anu feels the pain a moment later (pages 102-103, Fig. 6.2).

Question 2. Match each action to the part of the brain the chapter links it with: (a) your mouth watering when you smell hot samosas; (b) a batter timing a shot exactly; (c) working out the answer to a riddle; (d) feeling that you have eaten enough at lunch.

Answer: (a) medulla (hind-brain); (b) cerebellum (hind-brain); (c) fore-brain; (d) the hunger centre in the fore-brain. Salivation is one of the involuntary actions the medulla controls. The cerebellum is responsible for precise voluntary actions and balance. The fore-brain does most of the thinking, and the feeling of being full comes from a separate centre in it (pages 103-104).

Question 3. Rahul says: "The brain is protected only by the skull." Is he right? What else protects it, and what protects the spinal cord?

Answer: no. Inside the bony skull the brain sits in a fluid-filled balloon that absorbs shocks. The spinal cord is protected by the vertebral column, the backbone (page 105).

Question 4. Arrange from fastest to slowest response: (a) a root turning downwards after its pot is knocked over; (b) the leaves of a touch-me-not folding when brushed; (c) a sunflower turning between day and night. Say which one involves no growth.

Answer: (b), then (c), then (a); (b) involves no growth. The chapter calls the sensitive plant's response very quick, the sunflower's slow, and growth-related movement slower still. The root turning is geotropism, a growth movement. The touch-me-not leaves move because cells change their water content, with no growth (pages 105-107).

Question 5. Name the plant hormone at work in each case: (a) cells dividing quickly in a young mango fruit; (b) the leaves of a pot plant wilting; (c) a shoot growing longer on its shaded side.

Answer: (a) cytokinins; (b) abscisic acid; (c) auxin. Cytokinins promote cell division and are found in greater amounts in fruits and seeds. Abscisic acid holds back growth, and wilting is one of its effects. Auxin moves to the shady side of a shoot and makes those cells grow longer (page 108).

Question 6. Name the tropism in each case, and say whether the growth is towards or away from the stimulus: (a) a pollen tube growing down to an ovule; (b) tree roots spreading towards a leaking water pipe; (c) roots growing away from the light coming through a glass jar.

Answer: (a) chemotropism, towards; (b) hydrotropism, towards; (c) phototropism, away. The chapter gives the pollen tube as its example of chemotropism, defines hydrotropism as a response to water, and says roots bend away from light while shoots bend towards it (page 107).

Question 7. A stray dog suddenly chases Meera on her way home. Her smartwatch shows her heart rate jumping. (a) Which hormone and which gland are responsible? (b) Why does her heart beat faster? (c) Why does less blood go to her stomach and skin? (d) How does this hormone reach the heart?

Answer: (a) adrenaline, from the adrenal glands; (b) to send more oxygen to her muscles; (c) so that more blood reaches her skeletal muscles; (d) through the blood. Adrenaline goes straight into the blood and acts on target organs, including the heart. The small arteries of the digestive system and skin narrow, which diverts blood to the skeletal muscles, and breathing speeds up too, so her body is ready to run or to face the dog (page 109).

Question 8. A doctor finds that a child's growth hormone level is low. (a) Which part of the brain responds first, and with what? (b) Which gland then releases growth hormone? (c) What can a lasting shortage of growth hormone in childhood lead to? (d) Name the kind of control that keeps hormone levels from going too high or too low.

Answer: (a) the hypothalamus, by releasing growth hormone releasing factor; (b) the pituitary gland; (c) dwarfism; (d) a feedback mechanism. The chapter's box on page 110 describes this chain, and says a shortage of growth hormone in childhood leads to dwarfism. Page 111 explains that feedback mechanisms regulate the timing and amount of each hormone, using insulin and blood sugar as the example.

Revise with questions

Test yourself next: Class 10 Control and Coordination, 8 practice questions with answers. The other notes in this set: Life Processes, Metals and Non-metals and Heredity. For timed practice, the free Class 10 revision papers include a Science paper laid out in 1, 2, 3 and 5-mark sections.

Where CMDLearn fits

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Sources

All checked on 3 November 2026. NCERT page numbers are the printed page numbers of the textbook.

• NCERT, Science, Textbook for Class X, Chapter 6 "Control and Coordination" (Reprint 2026-27), pages 100-112: chapter opening (page 100); section 6.1 and Fig. 6.1 (pages 100-101); 6.1.1 and Fig. 6.2 (pages 102-103); 6.1.2 and Fig. 6.3 (pages 103-104); 6.1.3 and 6.1.4 (page 105); 6.2, Figs. 6.4 to 6.6 (pages 105-107); chemical communication and plant hormones (page 108); 6.3, Fig. 6.7, the "Do You Know?" box, Table 6.1 and "What you have learnt" (pages 109-111). ncert.nic.in/textbook/pdf/jesc106.pdf
• CBSE, Science curriculum, Class X, 2026-27: unit marks (PDF page 4) and Unit II contents (PDF page 5): cbseacademic.nic.in/web_material/CurriculumMain27/SecPart1/Science_SecP1_2026-27.pdf

The facts, section numbers and figure numbers are from the documents above. The wording of these notes, the diagram steps, the list of mistakes and the 8 questions are our own.

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