🧠 Control and Coordination ⚡
Class 10 Science • Biology • Complete Chapter Notes in Easy Language + Important CBSE Questions
🔔 1. Control and Coordination
🐾 2. Coordination in Animals
Animals coordinate their body in two ways:
1. Nervous system
Fast, uses electrical impulses.
2. Endocrine system
Slower, uses chemical messengers called hormones.
Parts of the nervous system
| Part | What it is |
|---|---|
| CNS | Brain and spinal cord |
| PNS – Cranial nerves | Arise from the brain |
| PNS – Spinal nerves | Arise from the spinal cord |
👁️ 3. Receptors and Effectors
| Receptor | Sense organ | Stimulus |
|---|---|---|
| Photo receptors | Eyes 👁️ | Light |
| Olfactory receptors | Nose 👃 | Smell |
| Gustatory receptors | Tongue 👅 | Taste |
| Phono receptors | Ear 👂 | Sound |
| Thermo receptors | Skin ✋ | Heat / Cold |
| Nociceptors | Skin ✋ | Pain |
🔗 4. Nerve and Neuron (Nerve Cell)
Neuron
- The structural and functional unit of the nervous system.
- The longest cell in the body.
- Carries messages as electrical impulses (signals).
Parts of a neuron
| Part | Job |
|---|---|
| Dendrite | Collects information (acquires it) |
| Cell body | Takes information from the dendrite in the form of an electrical impulse; has the nucleus |
| Axon | The electrical impulse travels along the axon |
| Myelin sheath | Covers the axon; prevents electrical signals from leaking out |
| Nerve ending | The electrical impulse here causes the release of chemicals |
🔌 5. Synapse
Role: to pass the electrical impulse from one neuron to another. At the synapse, the electrical impulse causes the release of chemicals (neurotransmitters) from the nerve ending of one neuron. These chemicals cross the synaptic gap and reach the dendritic tip of the next neuron, where they start a new electrical impulse.
Transmission of an impulse between 2 neurons
🧵 6. Types of Neurons and Neuromuscular Junction
| Type | Job |
|---|---|
| Sensory neurons | Carry the impulse from receptors to the CNS |
| Motor neurons | Carry the impulse from the CNS to effectors (muscle or gland) |
| Relay neurons / Interneurons | Connect sensory and motor neurons (inside the CNS) |
Example: touching something cold
(cold tea)
(skin)
(brain / spinal cord, relay neuron)
(muscle)
(leave the cup)
Neuromuscular Junction (NMJ)
- Muscle cells have specialised proteins that change their shape and arrangement in the cell when they receive nerve electrical impulses.
- Muscle cells move by changing their shape so that they shorten.
🚦 7. Voluntary, Involuntary and Reflex Actions
| Action | Thinking | Brain | Examples |
|---|---|---|---|
| Voluntary (controlled by will) | Involved ✔ | Involved ✔ | Walking, writing, dancing, talking |
| Involuntary | Not involved ✘ | Involved ✔ | Blood pumping by the heart, peristalsis, digestion |
| Reflex | Not involved ✘ | Not directly involved ✘ | Withdrawing a hand from a hot object, blinking when something comes close to the eye, sneezing |
⚡ 8. Reflex Action and Reflex Arc
Reflex arc for touching a hot object
Why are reflex arcs more efficient for quick responses?
- They skip the brain’s complex processing.
- They allow an instant reaction through the spinal cord.
- They reduce response time a lot.
🧠 9. The Brain – the Control Centre
The brain has 3 main parts: Fore-brain, Mid-brain and Hind-brain.
🔴 Fore-brain (the largest part)
- Main thinking part of the brain.
- Consists mainly of the cerebrum and the hypothalamus.
- Cerebrum controls hearing, memory, reasoning, speech, emotions, interpretation and all voluntary actions.
- Hypothalamus: controls hunger and thirst; controls the release of hormones from the endocrine system.
🟡 Mid-brain
- Connects the fore-brain and hind-brain.
- Controls some involuntary actions together with the hind-brain.
🔵 Hind-brain (Pons, Medulla, Cerebellum)
| Part | Job |
|---|---|
| Pons | Regulates breathing rate and sleep cycle |
| Medulla | Controls involuntary actions like blood pressure, heart beat, salivation and vomiting |
| Cerebellum | Precision of voluntary actions; maintains posture and balance of the body (picking up a pencil, riding a bicycle) |
🛡️ 10. Protection of the Brain and Spinal Cord
Brain
- Cranium – the bony box of the skull
- 3 thin membranes – Meninges
- CSF (cerebrospinal fluid) – absorbs shocks
Spinal cord
- Vertebral column (back bone)
- 3 thin membranes – Meninges
- CSF – absorbs shocks
🧪 11. Endocrine System
- A network of endocrine glands that make and release hormones.
- Hormones are chemical substances that act like messenger molecules in the body.
Glands, hormones and their jobs
| Gland | Hormone | Function | Related disease |
|---|---|---|---|
| Hypothalamus (fore-brain) | GHRH (Growth Hormone Releasing Hormone) | Stimulates the pituitary gland to release growth hormone | – |
| Pituitary gland | Growth hormone | Body growth; development of bones and muscles | Excess: gigantism Deficiency: dwarfism |
| Thyroid gland | Thyroxine | Regulates carbohydrate, protein and fat metabolism | Iodine deficiency: goitre (hypothyroidism) |
| Pancreas | Insulin | Controls blood sugar level | Diabetes |
| Adrenal gland | Adrenaline | Prepares the body to cope with emergency situations | – |
| Testes (males) | Testosterone | Development of male secondary characters: deep voice, beard, sex organs; changes at puberty | – |
| Ovaries (females) | Oestrogen | Development of female secondary characters like mammary glands, menstrual cycle, sex organs | – |
Where are the glands? (extra details)
- Pituitary: at the bottom of the hypothalamus; the master gland, releases many hormones.
- Thyroid: in the neck, below the larynx (voice box). Thyroxine needs iodine to be made — so use iodised salt in the diet. Deficiency of iodine causes goitre; the symptom is a swollen neck.
- Pancreas: in the upper abdomen, behind the stomach. Makes insulin; lack of insulin causes diabetes.
- Adrenal glands: sit above the kidneys.
⚔️ Adrenaline – the “Fight or Flight” (emergency) hormone ⭐
When you are scared or in an emergency, the adrenal gland releases adrenaline. Then:
- Heart beat increases (more oxygen supply to muscles).
- Blood to the digestive system and skin is reduced.
- Blood to the skeletal muscles increases.
- Breathing rate increases.
🔄 12. Feedback Mechanism
- Blood sugar level goes up → pancreas makes more insulin.
- Blood sugar level goes down → insulin release is reduced.
🌿 13. Coordination in Plants
- Plants do not have a nervous system like animals.
- The stimulus is passed on through a mix of electrical and chemical signals.
- These signals travel from cell to cell.
Movement in plants is of 2 types
🌻 14. Tropic Movement (Tropism)
- Growth movement of a plant part in response to an external stimulus is called tropism.
- It is growth-dependent.
- The direction of the stimulus decides the direction of the response.
- Growth towards the stimulus = positive tropism.
- Growth away from the stimulus = negative tropism.
| Tropism | Stimulus | Positive tropism | Negative tropism |
|---|---|---|---|
| Phototropism | Light | Stem (shoot) of a growing plant bends towards light | Roots move away from light |
| Geotropism | Gravity | Roots grow downward, towards gravity | Stem grows upward, against gravity |
| Hydrotropism | Water | Roots grow towards water | Movement away from water |
| Chemotropism | Chemicals | Growth of the pollen tube towards the ovule during fertilisation | Movement away from a chemical |
| Thigmotropism | Touch | Climbing parts such as tendrils grow towards a support and wind around it | – |
🙈 15. Nastic Movement
- Growth-independent movement.
- Example: when we touch the leaves of the sensitive plant Mimosa pudica (chhui-mui / touch-me-not), they fold.
- This happens because of a change in the amount of water in cells (cells swell or shrink).
Tropic vs Nastic movements
| Characteristic | Tropic movements | Nastic movements |
|---|---|---|
| Response to stimulus | Directional (towards/away) | Non-directional |
| Depends on growth? | Growth-dependent | Growth-independent |
| Nature of movement | Permanent and irreversible | Temporary and reversible |
| Where found | In all plants | Only in a few specialised plants |
| Speed | Slow action | Immediate (fast) action |
Animals vs Plants (how they coordinate) ⭐
| Animals | Plants |
|---|---|
| Have specialised tissues (nerves) to carry information | Have no specialised tissues to carry information |
| Movement happens because of specialised proteins in muscles | Movement happens because of a change in the amount of water in cells (swelling / shrinking) |
🧴 16. Plant Hormones
| Plant hormone | Function |
|---|---|
| Auxin (growth promoter, GP) | Promotes cell elongation in shoots; controls phototropism |
| Gibberellins (GP) | Help the stem to grow longer; present in higher amounts in fruits and seeds |
| Cytokinin (GP) | Promotes cell division; delays ageing of leaves and flowers |
| Abscisic acid (growth inhibitor, GI) – “stress hormone” | Makes stomata close; keeps seeds dormant; causes wilting of leaves |
Why does a plant bend towards light? ⭐ (CBSE 2025, 2022, 2019)
🎯 17. Important CBSE Questions with Answers
Q1. What is meant by receptors in the human body? Name any four types of receptors with their locations. CBSE 2025, 24, 23, 20, 18
Receptors are cells, tissues or organs that receive stimuli from the environment. Four types: Photoreceptors – eyes (light); Olfactory receptors – nose (smell); Gustatory receptors – tongue (taste); Phonoreceptors – ear (sound). (Also: thermoreceptors and nociceptors in skin.)
Q2. Draw a neuron and label: (a) where information is acquired, (b) through which information travels as an electric impulse, (c) where the electric impulse is changed into a chemical signal. CBSE 2019, 18
(a) Dendrite (b) Axon (c) Nerve ending. (See the neuron diagram in Section 4.)
Q3. Electrical impulse travels in a neuron from: CBSE 2025, 19, 18
✅ (B) Dendrite → Cell body → Axon → Nerve ending
Q4. What is a synapse? How is an electrical impulse created in a nerve cell and what is the role of the synapse? CBSE 2025, 19, 15
A synapse is the microscopic gap between the nerve ending of one neuron and the dendritic tip of the next neuron. In a neuron, the impulse is created by a difference in potential, caused by the movement of ions across the neuron’s membrane. At the synapse, the impulse makes the nerve ending release chemicals; these cross the gap and reach the dendritic tip of the next neuron, creating a new electrical impulse there. So the synapse passes the signal from one neuron to the next.
Q5. Ravi touches a hot pan while cooking and quickly pulls his hand away. (1) Sequence of events? (2) Define reflex action and show the path as a flowchart. (3) Why are reflex arcs more efficient for quick responses? CBSE 2024
(1)/(2) Stimulus (heat) → Thermo receptor → Sensory neuron → Spinal cord (interneuron) → Motor neuron → Effector (muscles) → Response (hand moves away).
A reflex action is a sudden, quick and involuntary movement in which thinking is not involved. It is controlled by the spinal cord and protects the body with a quick reaction.
(3) Reflex arcs (i) skip the brain’s complex processing, (ii) allow an instant reaction through the spinal cord, (iii) reduce response time greatly.
Q6. Explain how the brain and spinal cord are protected from shocks and injuries. CBSE 2023, 20
Brain: bony cranium (skull), three thin membranes called meninges, and cerebrospinal fluid (CSF) which absorbs shocks. Spinal cord: vertebral column (back bone), the same meninges, and CSF.
Q7. Which of these is NOT controlled by the part of the brain marked ‘X’ (hind-brain)? (A) Salivation (B) Hunger (C) Vomiting (D) Blood pressure CBSE 2025
✅ (B) Hunger — hunger is controlled by the hypothalamus (fore-brain). Salivation, vomiting and blood pressure are controlled by the medulla.
Q8. Which part of the brain is responsible for: (a) thinking (b) picking up a pencil (c) controlling blood pressure (d) controlling hunger? CBSE 2025, 24, 23, 20
✅ (A) (a) Cerebrum, (b) Cerebellum, (c) Medulla oblongata, (d) Hypothalamus.
Q9. Which parts of the brain are responsible for (a) maintaining posture and balance (b) controlling heartbeat (c) enabling thinking (d) regulating blood pressure? CBSE 2023, 20
(a) Cerebellum (b) Medulla (c) Cerebrum (fore-brain) (d) Medulla
Q10. Which gland secretes thyroxine and what is its main function? CBSE 2025, 24, 23, 20
✅ (B) Thyroid gland – regulates the metabolism of carbohydrates, proteins and fats.
Q11. (A) Write the role of insulin in regulating blood sugar. Name the disease caused due to it. (B) How is the timing and amount of insulin release regulated? CBSE 2025, 23, 20, 17, 16, 15
(A) Insulin lowers blood glucose. After a meal, blood glucose rises; insulin helps body cells take up glucose to use for energy or store it as glycogen. If the body does not make enough insulin, the disease diabetes mellitus occurs.
(B) By the feedback mechanism: higher blood glucose → more insulin released; lower blood glucose → less insulin released.
Q12. What hormone does the adrenal gland release in stress? What three responses does the body show? CBSE 2024, 23, 20
The adrenal glands (on top of each kidney) release adrenaline (the emergency / fight-or-flight hormone). Responses: (1) heart rate increases (more oxygen to muscles), (2) blood to the digestive system and skin is reduced, (3) blood to skeletal muscles increases. (Breathing rate also increases.)
Q13. A hormone ‘X’ is released when a person is in a scary situation. (a) Identify the hormone and its gland. (b) Explain its role. CBSE 2025
(a) Adrenaline, secreted by the adrenal gland. (b) It prepares the body for an emergency: heart beat and breathing rate increase, blood flow to the skeletal muscles increases, and blood flow to the digestive system and skin decreases — so the body can fight or run.
Q14. (i) Where is the thyroid gland? Name its hormone and explain its function. (ii) What is hypothyroidism? How can it be managed? CBSE 2024, 23, 20
(i) The thyroid gland is in the front of the neck, just below the larynx. It secretes thyroxine, which regulates carbohydrate, protein and fat metabolism.
(ii) Hypothyroidism is a condition in which the thyroid does not make enough thyroid hormone, often due to iodine deficiency. This can cause goitre (swelling of the neck). It can be managed by taking iodised salt in the diet.
Q15. State two limitations of electrical impulses in multicellular organisms. Why is chemical communication better? ⭐ IMPORTANT CBSE 2025
Limitations of electrical impulses:
1. Limited range – they reach only cells connected to the nervous system, not every cell in the body.
2. Reset time – after a neuron sends an impulse, it needs some time to reset before it can send another, which limits how often it can signal.
Why chemical communication is better:
1. Wider range – chemicals (hormones) spread through the blood and reach all cells.
2. Slow but long-lasting effects – needed for growth, metabolism, etc.
3. Targeted – they act only on cells with the matching receptors.
Q16. Name the movement which makes ‘X’ (root) grow downwards and ‘Y’ (shoot) grow upwards. CBSE 2025, 22, 20, 19
Geotropic movement – the stimulus is gravity. Roots show positive geotropism (down); shoots show negative geotropism (up).
Q17. When the chhui-mui (sensitive) plant is touched, its leaves fold. This is due to: (A) Hormonal effect (B) Thermal effect (C) Change in amount of water in cells (D) Electromagnetic effect CBSE 2025, 24, 16
✅ (C) Change in the amount of water in cells. (It is a nastic movement.)
Q18. Leaves of the sensitive plant move very quickly on touch. How is this stimulus communicated and how does the movement happen? CBSE 2025, 22, 20, 19
The stimulus is not sent through a nervous system as in animals. It is passed on by a mix of electrical and chemical signals that travel from cell to cell. This is a nastic movement and happens immediately. The leaves move because of a change in the amount of water in cells (they swell or shrink).
Q19. Plant hormones that promote rapid cell division in seeds and cause wilting of leaves, respectively, are: (A) Auxins and Abscisic acid (B) Cytokinins and Abscisic acid (C) Gibberellins and Auxins (D) Abscisic acid and Gibberellins CBSE 2025, 24
✅ (B) Cytokinins and Abscisic acid
Q20. The plant hormone that makes cells grow longer on the side of the shoot away from light is: (A) Cytokinins (B) Gibberellins (C) Adrenaline (D) Auxins CBSE 2025
✅ (D) Auxins
⚡ Quick Revision Points
- Stimulus → receptor → sensory neuron → CNS → motor neuron → effector → response.
- Neuron path: Dendrite → Cell body → Axon → Nerve ending; at the synapse, chemicals carry the signal across the gap.
- Reflex action: spinal cord, no thinking, quick, protects the body. Voluntary: cerebrum (thinking).
- Fore-brain: cerebrum + hypothalamus. Mid-brain: connects. Hind-brain: PMC – Pons, Medulla, Cerebellum.
- Brain protected by cranium + meninges + CSF; spinal cord by vertebral column + meninges + CSF.
- Hormones: Growth hormone (pituitary), thyroxine (thyroid, needs iodine), insulin (pancreas), adrenaline (adrenal), testosterone (testes), oestrogen (ovaries).
- Hormone release is controlled by feedback (e.g. blood sugar and insulin).
- Plants: tropic (growth-dependent, directional, slow) vs nastic (growth-independent, fast, due to water change).
- Plant hormones: Auxin, Gibberellins, Cytokinin promote growth; Abscisic acid inhibits growth.
🌟 All the best for your exams! 🌟