Control and Coordination
Class 10 Science complete NCERT-based notes covering coordination in plants, nervous system, reflex action, brain, spinal cord, endocrine glands, hormones and feedback mechanism.
1 Chapter Overview
What will you learn?
- How living organisms detect changes around them.
- How plants coordinate without a nervous system.
- How neurons, nerves, brain and spinal cord control animals.
- How hormones regulate slow and long-lasting responses.
Why is this chapter important?
This chapter explains how the body behaves like a highly organised control system. Every response, from pulling your hand away from a hot object to maintaining blood sugar level, depends on proper coordination.
Exam relevance
CBSE frequently asks questions from reflex arc, neuron diagram, brain parts, tropic movements, plant hormones, endocrine glands and feedback mechanism.
2 Table of Contents
3 Introduction to Control and Coordination
Meaning of Control and Coordination
Living organisms constantly receive information from their surroundings and from inside their bodies. They respond to these changes in a controlled and coordinated manner. This ability is called control and coordination.
Control means regulation of body activities. Coordination means working together of different organs so that the organism gives a proper response to a stimulus.
Basic pathway of response
Examples from daily life
- Touching a hot pan makes you quickly withdraw your hand.
- Pupil size changes according to light intensity.
- Roots grow towards water and gravity.
- Adrenaline prepares the body during fear, anger or stress.
Plants mainly use chemical coordination through hormones. Animals use both nervous coordination and hormonal coordination.
4 Control and Coordination in Plants
Do plants have a nervous system?
No. Plants do not have nerves, brain or muscles. Still, they respond to light, gravity, touch, water and chemicals. Their coordination is mainly controlled by plant hormones and changes in growth.
Two major types of plant responses
| Type of response | Meaning | Example |
|---|---|---|
| Growth-dependent movement | Movement caused by unequal growth in different parts of the plant. | Shoot bending towards light. |
| Growth-independent movement | Movement not caused by growth, usually due to changes in water content or turgor pressure. | Leaves of touch-me-not folding on touch. |
In board answers, write that plants coordinate by using hormones and growth responses, not by nerves.
5 Tropic and Nastic Movements in Plants
A. Tropic Movements
Tropic movements are directional growth movements of plant parts in response to an external stimulus. If the plant part grows towards the stimulus, it is called positive tropism. If it grows away from the stimulus, it is called negative tropism.
| Movement | Stimulus | Positive response | Negative response |
|---|---|---|---|
| Phototropism | Light | Shoot grows towards light. | Root usually grows away from strong light. |
| Geotropism / Gravitropism | Gravity | Root grows towards gravity. | Shoot grows away from gravity. |
| Hydrotropism | Water | Roots grow towards water. | Less commonly discussed at Class 10 level. |
| Chemotropism | Chemicals | Pollen tube grows towards ovule. | Growth away from harmful chemicals. |
| Thigmotropism | Touch or support | Tendrils coil around support. | Not usually asked as negative thigmotropism in Class 10. |
Auxin collects on the shaded side of the shoot. In shoots, auxin promotes cell elongation. The shaded side grows faster than the illuminated side, so the shoot bends towards light.
B. Nastic Movements
Nastic movements are non-directional movements of plant parts. The response does not depend on the direction of the stimulus.
| Feature | Tropic movement | Nastic movement |
|---|---|---|
| Direction | Directional; depends on direction of stimulus. | Non-directional; does not depend on direction of stimulus. |
| Cause | Usually growth-based. | Usually due to turgor changes. |
| Speed | Slow. | Often faster. |
| Example | Shoot bending towards light. | Touch-me-not leaves folding on touch. |
Do not call touch-me-not movement thigmotropism. It is a nastic movement because the leaves fold irrespective of the direction of touch.
6 Phytohormones: Plant Hormones and Their Functions
What are phytohormones?
Phytohormones are chemical substances produced in plants in very small amounts. They regulate growth, development, flowering, fruit ripening and responses to stimuli.
| Plant hormone | Main functions | Board example |
|---|---|---|
| Auxin | Promotes cell elongation, helps in phototropism, helps in root/shoot growth regulation. | Shoot bends towards light due to unequal auxin distribution. |
| Gibberellin | Promotes stem elongation, seed germination and growth. | Helps plants grow taller. |
| Cytokinin | Promotes cell division and growth of shoots/buds. | More active in areas where rapid cell division occurs. |
| Abscisic acid | Inhibits growth, promotes dormancy, helps in closing stomata during water stress. | Known as a growth inhibitor. |
| Ethylene | Promotes fruit ripening and ageing of plant parts. | Ripening of bananas and mangoes. |
Auxin has different effects in shoots and roots. In shoots, suitable auxin concentration promotes elongation. In roots, high auxin concentration can inhibit elongation. This helps explain why roots and shoots respond differently to gravity.
Auxin, gibberellin, cytokinin and abscisic acid are the most important plant hormones for Class 10 board answers.
7 Coordination in Animals
Why do animals need faster coordination?
Animals move from place to place, search for food, escape danger and interact with changing surroundings. Therefore, they require quick and precise coordination.
Two systems of coordination in animals
| System | Nature of message | Speed | Effect | Example |
|---|---|---|---|---|
| Nervous system | Electrical and chemical impulses | Very fast | Short-lived and specific | Reflex action |
| Endocrine system | Chemical hormones in blood | Slower | Long-lasting and widespread | Growth, metabolism, puberty |
8 Neuron, Nerve Impulse and Synapse
Neuron: Structural and Functional Unit of Nervous System
A neuron is a specialised nerve cell that receives, conducts and transmits information in the form of nerve impulses.
Receive impulse
Nucleus present
Carries impulse away
Passes signal to next cell
Parts of a neuron
- Dendrites: Short branched structures that receive information.
- Cell body: Contains nucleus and cytoplasm.
- Axon: Long fibre that carries impulse away from the cell body.
- Nerve endings: Release chemicals to transfer signal to the next neuron or effector.
Types of neurons
| Type | Function | Example role |
|---|---|---|
| Sensory neuron | Carries impulse from receptor to CNS. | Skin receptor to spinal cord. |
| Motor neuron | Carries impulse from CNS to effector. | Spinal cord to muscle. |
| Interneuron / Relay neuron | Connects sensory and motor neurons inside CNS. | Important in reflex arc. |
Synapse
A synapse is a small gap between the nerve ending of one neuron and the dendrite of the next neuron, or between a neuron and an effector.
Synapse allows controlled transfer of information. It prevents random mixing of impulses and ensures that signals pass to the correct next cell.
Chemical neurotransmitters are released only from the nerve ending of the first neuron and received by receptors on the next neuron. Therefore, the impulse usually travels in one direction only.
9 Reflex Action and Reflex Arc
Reflex Action
A reflex action is a quick, automatic and involuntary response to a stimulus. It protects the body from harm.
Reflex arc is the pathway followed by nerve impulses during a reflex action.
Example: Touching a hot object
- Heat acts as stimulus.
- Receptors in skin detect heat/pain.
- Sensory neuron carries impulse to spinal cord.
- Spinal cord sends command through motor neuron.
- Arm muscles contract and hand is withdrawn.
In reflex action, the spinal cord gives the immediate response, while the brain becomes aware of the pain shortly after.
| Reflex action | Voluntary action |
|---|---|
| Automatic and involuntary. | Under conscious control. |
| Very fast. | Usually slower than reflex action. |
| Controlled mainly by spinal cord. | Controlled by brain. |
| Example: Withdrawal of hand from hot object. | Example: Writing, walking, picking a book. |
10 Human Nervous System
Major divisions
| Division | Components | Function |
|---|---|---|
| Central Nervous System | Brain and spinal cord | Receives, processes and sends commands. |
| Peripheral Nervous System | Cranial nerves and spinal nerves | Connects CNS with body organs. |
| Somatic Nervous System | Nerves controlling skeletal muscles | Voluntary actions. |
| Autonomic Nervous System | Sympathetic and parasympathetic divisions | Involuntary actions like heartbeat, digestion, breathing rate. |
Nerves
A nerve is a bundle of nerve fibres/axons covered by protective tissue. Nerves carry impulses between the CNS and body parts.
| Type of nerve | Meaning |
|---|---|
| Sensory nerve | Carries information from receptors to CNS. |
| Motor nerve | Carries commands from CNS to muscles or glands. |
| Mixed nerve | Contains both sensory and motor fibres. |
| Cranial nerve | Nerve arising from the brain. It connects brain with head, neck and some internal organs. |
| Spinal nerve | Nerve arising from the spinal cord. It connects spinal cord with body parts. |
| Visceral nerve | Nerve associated with internal organs. It mainly works under the autonomic nervous system. |
Sympathetic nerves prepare the body for emergency conditions. Parasympathetic nerves help the body return to normal rest-and-digest condition.
11 Brain and Spinal Cord
Human Brain
The brain is the main control centre of the body. It receives information, interprets it, stores memory, controls emotions, coordinates movement and regulates involuntary activities.
| Part of brain | Main functions |
|---|---|
| Cerebrum | Thinking, memory, intelligence, emotions, voluntary actions and interpretation of sensory information. |
| Hypothalamus | Regulates body temperature, hunger, thirst and links nervous system with endocrine system. |
| Midbrain | Controls some visual and auditory reflexes. |
| Cerebellum | Coordinates muscular movement, posture and body balance. |
| Pons | Acts as a bridge between parts of brain and helps in breathing regulation. |
| Medulla oblongata | Controls involuntary actions like heartbeat, breathing, swallowing and blood pressure. |
Do not write that cerebellum controls thinking. Thinking and memory are mainly functions of cerebrum. Cerebellum controls balance and coordination of movement.
Spinal Cord
The spinal cord is a long cylindrical nervous tissue extending from the medulla oblongata through the vertebral column. It carries impulses between brain and body and controls many reflex actions.
Functions of spinal cord
- Conducts sensory impulses from body to brain.
- Conducts motor commands from brain to body.
- Acts as reflex centre for many reflex actions.
Protection of brain and spinal cord
| Organ | Protection |
|---|---|
| Brain | Skull/cranium, meninges and cerebrospinal fluid. |
| Spinal cord | Vertebral column/backbone, meninges and cerebrospinal fluid. |
Cerebrospinal fluid protects the brain and spinal cord from mechanical shocks and also helps maintain a stable environment around them.
12 Hormonal System and Endocrine Glands
Endocrine System
The endocrine system consists of glands that secrete hormones directly into the blood. Hormones act as chemical messengers and regulate growth, metabolism, reproduction, stress response and internal balance.
Hormones are chemical substances secreted by endocrine glands in small amounts. They are carried by blood to target organs where they produce specific effects.
| Gland | Hormone | Main function | Exam importance |
|---|---|---|---|
| Hypothalamus | Releasing and inhibiting hormones | Controls pituitary gland and links nervous system with endocrine system. | Foundation Edge |
| Pituitary gland | Growth hormone, TSH, FSH, LH and others | Controls growth and regulates many other endocrine glands. | Very important |
| Pineal gland | Melatonin | Regulates sleep-wake cycle. | Foundation Edge |
| Thyroid gland | Thyroxine | Regulates metabolism. Requires iodine for production. | Very important |
| Parathyroid glands | Parathyroid hormone | Regulates calcium level in blood. | Foundation Edge |
| Pancreas | Insulin and glucagon | Regulates blood sugar level. | Very important |
| Adrenal glands | Adrenaline | Prepares body for emergency: increases heartbeat, breathing rate and blood supply to muscles. | Very important |
| Testes | Testosterone | Controls male secondary sexual characters and sperm formation. | Important |
| Ovaries | Oestrogen and progesterone | Control female secondary sexual characters, menstrual cycle and pregnancy-related changes. | Important |
Dual Gland
A dual gland performs both endocrine and exocrine functions.
Pancreas acts as an endocrine gland by secreting insulin and glucagon into blood. It also acts as an exocrine gland by secreting digestive enzymes through ducts into the small intestine.
Gonads such as testes and ovaries also have dual roles because they produce gametes and secrete hormones. However, for Class 10 board answers, pancreas is the safest example of a dual gland.
13 Feedback Mechanism
What is feedback mechanism?
A feedback mechanism is a regulatory process in which the level of a substance or hormone controls further secretion of that hormone. It helps maintain internal balance or homeostasis.
Feedback mechanism is often asked through the example of blood sugar control by insulin or thyroid regulation by pituitary gland.
14 Important Terms
15 Board Exam Focus + Competitive Edge
Most Important Board Points
- Draw and label neuron properly.
- Write reflex arc in correct sequence.
- Differentiate tropic and nastic movements.
- Explain auxin role in phototropism.
- Learn functions of cerebrum, cerebellum and medulla.
- Learn hormones: thyroxine, insulin, adrenaline, growth hormone, testosterone and oestrogen.
- Use correct terms: receptor, sensory neuron, spinal cord, motor neuron, effector.
Foundation/Olympiad Edge
- Synaptic transmission is chemical and usually one-directional.
- Reflex action reduces response time and protects the body.
- Hypothalamus connects nervous and endocrine systems.
- Pancreas is both endocrine and exocrine.
- Sympathetic and parasympathetic systems often have opposite effects.
- Feedback mechanism maintains homeostasis.
16 Common Mistakes
- Writing that plants have nerves. They do not.
- Confusing tropic movement with nastic movement.
- Writing reflex action is controlled by brain only. Immediate response is usually through spinal cord.
- Confusing cerebrum with cerebellum.
- Forgetting that hormones travel through blood.
- Writing that all glands have ducts. Endocrine glands are ductless.
- Using “adrenaline” for digestion. Adrenaline is for emergency response.
17 Practice Questions
MCQs
A. Nephron B. Neuron C. Alveolus D. Villus
A. Auxin B. Insulin C. Thyroxine D. Adrenaline
A. Cerebrum B. Cerebellum C. Thyroid D. Spinal cord
A. Phototropism B. Hydrotropism C. Chemotropism D. Geotropism
A. Thyroid B. Adrenal C. Pancreas D. Pituitary
Fill in the blanks
True or False
Assertion-Reason
Reason: Reflex actions often involve spinal cord and do not wait for conscious decision by brain.
Reason: Neurotransmitters are released from nerve endings and received by receptors on the next cell.
Reason: Auxin collects on shaded side and promotes more cell elongation there.
Very Short Answer Questions
Short Answer Questions
Long Answer Questions
Case Study Based Questions
a. Name the movement shown by the shoot.
b. Which hormone is responsible?
c. Why does the shoot bend towards light?
d. Name the movement shown by roots growing downward.
a. Which hormone is mainly responsible?
b. Which gland secretes it?
c. Why is this response useful?
d. Is this response nervous, hormonal or both?
No Numericals Note
18 Answer Key
MCQs
1. B 2. A 3. B 4. C 5. C
Fill in the blanks
6. Synapse 7. Adrenaline 8. Geotropism/Gravitropism 9. Blood 10. Skull/Cranium
True or False
11. False 12. True 13. True 14. False
Assertion-Reason
15. Both A and R are true, and R correctly explains A.
16. Both A and R are true, and R correctly explains A.
17. Both A and R are true, and R correctly explains A.
Very Short Answers
18. A stimulus is any change in the environment that produces a response.
19. Thyroxine.
20. Cerebellum controls balance, posture and coordination of muscular movement.
21. Abscisic acid.
22. A receptor is a specialised structure that detects a stimulus.
Short/Long Answer Key Points
23. Tropic movements are directional growth movements; nastic movements are non-directional and often turgor-based.
24. Auxin accumulates on the shaded side of shoot, promotes more elongation there and causes bending towards light.
25. Reflex action protects the body by producing quick automatic responses without waiting for conscious decision.
26. Nervous coordination is fast, electrical/chemical, short-lived and specific; hormonal coordination is slower, chemical, blood-borne and longer-lasting.
27. Cerebrum controls thinking and voluntary actions; cerebellum controls balance; medulla controls involuntary actions.
28. Draw dendrites, cell body, nucleus, axon and nerve endings. Explain direction of impulse.
29. Include receptor, sensory neuron, spinal cord, motor neuron and effector muscle in correct sequence.
30. Mention pituitary, thyroid, pancreas, adrenal, testes and ovaries with hormones and functions.
Case Study Answers
31. a. Phototropism b. Auxin c. More auxin on shaded side causes more elongation d. Positive geotropism.
32. a. Adrenaline b. Adrenal gland c. Prepares body for fight-or-flight d. Both nervous and hormonal coordination are involved.
19 Quick Revision Mind Map + Final Sheet
One-Page Final Revision
Control and Coordination
Stimulus → Receptor → Coordinator → Effector → Response
Plants
- No nervous system.
- Coordination through hormones and growth responses.
- Tropic movement: directional growth response.
- Nastic movement: non-directional response.
- Auxin: cell elongation, phototropism.
- Gibberellin: stem growth.
- Cytokinin: cell division.
- Abscisic acid: growth inhibitor.
Nervous System
- Neuron: dendrite, cell body, axon, nerve ending.
- Synapse: gap between neurons; one-way transmission.
- Reflex arc: receptor → sensory neuron → spinal cord → motor neuron → effector.
- CNS: brain and spinal cord.
- PNS: cranial and spinal nerves.
- ANS: controls involuntary organs.
Brain
- Cerebrum: thinking, memory, voluntary action.
- Cerebellum: balance and posture.
- Medulla: breathing, heartbeat and other involuntary actions.
- Brain protected by skull, meninges and cerebrospinal fluid.
- Spinal cord protected by vertebral column.
Hormones
- Pituitary: growth hormone, master gland role.
- Thyroid: thyroxine, metabolism, iodine needed.
- Pancreas: insulin and glucagon, blood sugar control.
- Adrenal: adrenaline, emergency response.
- Testes: testosterone.
- Ovaries: oestrogen and progesterone.
Most Likely CBSE Questions
- Explain reflex arc with diagram.
- Draw and label a neuron.
- Differentiate between tropic and nastic movement.
- Explain role of auxin in phototropism.
- Write functions of cerebrum, cerebellum and medulla.
- Compare nervous and hormonal coordination.
- Explain feedback mechanism with example.
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