MP Board Class 10 Science Chapter 6: Control and Coordina…
MP Board Class 10 Science Chapter 6: Control and Coordination (नियंत्रण एवं समन्वय) — This chapter explains how living organisms respond to stimuli and coordinate their activities through the nervous system and endocrine system. Carrying 8–12 marks in the MP Board Class 10 Science exam, Control and Coordination is a key biology chapter. This guide covers the human nervous system, brain structure, reflex actions, hormones in animals and plants, with detailed explanations and previous year questions.
📑 Table of Contents
🧠 1. The Nervous System — An Overview
All living organisms respond to changes in their environment. These changes are called stimuli (singular: stimulus). The ability to respond to stimuli is called irritability. In animals, control and coordination is achieved through the nervous system and endocrine system (hormonal system).
Components of the Nervous System
Types of Nervous System
- Central Nervous System (CNS) — Brain + Spinal Cord
- Peripheral Nervous System (PNS) — All nerves outside CNS
🔬 2. Neuron — Structure and Function
The neuron is the structural and functional unit of the nervous system. It is specialized for conducting nerve impulses.
Structure of a Neuron
- Dendrites — Branched extensions that receive electrical signals from other neurons or sensory receptors
- Cell Body (Soma) — Contains nucleus and cytoplasm, processes the signals
- Axon — Long, single fibre that carries impulse away from cell body
- Myelin Sheath — Insulating layer (fatty substance) that speeds up impulse transmission
- Axon Terminals (Synaptic Knobs) — Branched endings that release neurotransmitters to pass signal to next neuron
How a Nerve Impulse Travels
- Stimulus detected by dendrites of sensory neuron
- Impulse travels along axon as electrical signal
- At the synapse (gap between two neurons), chemical messengers called neurotransmitters are released
- Neurotransmitter binds to dendrites of next neuron, generating a new impulse
📘 Key Fact: A synapse is NOT a physical connection — there’s a tiny gap called the synaptic cleft (~20 nm). Neurotransmitters like acetylcholine, dopamine, and serotonin carry the signal across this gap.
⚡ 3. Reflex Actions and Reflex Arc
Reflex action is a quick, automatic, involuntary response to a stimulus. It does not involve conscious thought — the brain is informed after the response occurs. Examples: pulling hand away from a hot object, knee jerk, blinking when something approaches the eye.
The Reflex Arc
The reflex arc is the nerve pathway that controls a reflex action. It involves:
- Receptor — Detects the stimulus (e.g., pain receptors in skin)
- Sensory Neuron — Carries impulse to spinal cord
- Spinal Cord (Relay Neuron) — Processes and relays the impulse
- Motor Neuron — Carries response impulse to effector
- Effector — Muscle or gland that produces the response
🧠 4. Human Brain — Structure and Parts
The human brain is the main coordinating centre of the body. It is protected by the skull (cranium) and three layers of membranes called meninges. The brain is divided into three major parts:
Major Parts of the Brain
Key Brain Functions
- Cerebrum — Largest part (85% of brain mass), divided into left and right hemispheres. Controls voluntary actions, speech, intelligence, memory, and sensory perception. The left hemisphere controls the right side of the body and vice versa.
- Cerebellum — Controls posture, balance, and voluntary muscle coordination. Damage affects precise movements (e.g., walking straight).
- Medulla Oblongata — Controls involuntary actions: heartbeat, breathing, blood pressure, swallowing, coughing, sneezing.
- Hypothalamus — Regulates body temperature, hunger, thirst, sleep, and emotional behaviour. Links the nervous system to the endocrine system.
📘 Key Fact: The brain is protected by cerebrospinal fluid (CSF) that acts as a shock absorber. It weighs about 1.3–1.4 kg in adults and contains ~100 billion neurons.
Protection of the Brain and Spinal Cord
- Skull (Cranium) — Bony protection for brain
- Vertebral Column (Backbone) — Protects spinal cord
- Meninges — Three layers of membranes (Dura mater, Arachnoid mater, Pia mater)
- Cerebrospinal Fluid (CSF) — Shock-absorbing fluid between meningeal layers
🌱 5. Coordination in Plants
Plants do not have a nervous system, but they still respond to stimuli. They respond through hormones and movements. Plant movements are of two types:
Tropic Movements (Growth Movements)
Directional growth movements in response to stimuli. The direction of response depends on the direction of the stimulus.
Nastic Movements (Non-directional)
Movements that occur in response to a stimulus but the direction is independent of the stimulus direction.
- Thigmonasty (Seismonasty) — Response to touch. Example: Mimosa pudica (Touch-me-not/Chhui-Mui) leaves fold when touched. This happens due to loss of water from cells at the base of leaflets.
- Photonasty — Response to light. Example: Flowers of some plants open in morning (dandelion) and close at night.
Plant Hormones (Phytohormones)
Plants produce chemical substances called plant hormones that regulate growth and responses to stimuli.
🧪 6. Hormones in Animals — Endocrine System
The endocrine system works alongside the nervous system for control and coordination. Hormones are chemical messengers secreted by endocrine glands (ductless glands) directly into the blood. They act on specific target organs.
Major Endocrine Glands and Their Hormones
Feedback Mechanism
The endocrine system uses feedback mechanisms to maintain hormone levels:
- Negative Feedback — Increase in hormone level causes decrease in its production (e.g., thyroxine, insulin). Most common type.
- Positive Feedback — Increase in hormone level causes further increase in production (e.g., oxytocin during childbirth).
📘 Key Fact: Adrenaline is also called the emergency hormone or fight-or-flight hormone. It prepares the body for stressful situations by increasing heart rate, breathing rate, blood glucose, and diverting blood to muscles.
📋 Previous Year Questions (2018–2026)
📝 Practice Questions for 2027 Exam
Q1: Draw a labelled diagram of a neuron. Explain how a nerve impulse travels across a synapse.
Answer: A neuron has dendrites, cell body, axon, myelin sheath, and axon terminals. At the synapse, the electrical impulse triggers release of neurotransmitters (e.g., acetylcholine) from synaptic vesicles. These chemicals diffuse across the synaptic cleft and bind to receptors on the next neuron’s dendrites, generating a new electrical impulse. This ensures one-way transmission of nerve signals.
Q2: Why is the pituitary gland called the “master gland”? Name any two hormones it secretes and their functions.
Answer: The pituitary gland is called the master gland because it controls the functioning of other endocrine glands (thyroid, adrenal, gonads). Hormones: (1) Growth Hormone (GH) — regulates body growth and development. (2) Thyroid Stimulating Hormone (TSH) — stimulates thyroid gland to produce thyroxine.
Q3: What is the difference between a reflex action and a voluntary action? Give one example of each.
Answer: Reflex action is involuntary, automatic, fast, and controlled by the spinal cord (e.g., pulling hand away from hot object). Voluntary action is conscious, controlled by the brain, and takes more time (e.g., writing your name, picking up a book). Reflex actions protect the body from harm by providing immediate response without waiting for brain processing.
Q4: Write the functions of each part of the human brain. Which part controls balance and coordination?
Answer: Forebrain (cerebrum, hypothalamus): thinking, memory, voluntary actions, homeostasis. Midbrain: visual and auditory reflexes. Hindbrain: cerebellum (balance & coordination), pons (sleep, breathing), medulla (heartbeat, breathing, swallowing). The cerebellum specifically controls balance and coordination of voluntary muscles. Damage to it causes loss of balance and uncoordinated movements.
Q5: Explain phototropism with the help of the role of auxin.
Answer: Phototropism is the growth of a plant towards (positive) or away from (negative) light. When light falls from one side, auxin (produced at the tip) moves to the shaded side of the stem. Higher auxin concentration on the shaded side stimulates more cell elongation there, causing the stem to bend towards the light source. This helps plants maximise light absorption for photosynthesis.
📌 Exam Tips for MP Board Class 10 Science 2027
- 🔥 High-weightage topics: Neuron structure & synapse, reflex arc, brain parts & functions, plant hormones (especially auxin), endocrine glands & their hormones — these cover 60% of the marks in this chapter.
- 📝 Diagram practice: Practice drawing labelled diagrams of neuron, brain (with all 3 parts), and reflex arc. Neat diagrams with proper labels can fetch full 5 marks.
- 🧪 Hormones table: Memorise the gland → hormone → function table for animals. For plants, remember auxin (growth/phototropism), gibberellin (elongation), cytokinin (cell division), ABA (stress/inhibition), ethylene (ripening).
- ⚡ Comparison questions: Be ready for “Differentiate between” questions: nervous vs endocrine, reflex vs voluntary, tropic vs nastic, sensory vs motor neuron, CNS vs PNS.
- ⚠️ Common mistakes: (1) Confusing cerebellum (balance) with cerebrum (thinking). (2) Thinking plants have nerves (they don’t — only hormones). (3) Mixing up adrenaline (emergency hormone) with thyroxine (metabolism).
- 📊 Mark distribution: Typically 2-3 marks for short-answer (neuron, reflex arc), 3-5 marks for long-answer (brain structure, hormone table, tropism explanation). Diagram-based questions carry 5 marks.
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