CBSE Class 10/Overview
Curriculum 2026–27
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ScienceCh-6 15 min comprehensive revision
NCERT Class 10 Science — Chapter 7

Control and Coordination

Nervous system, neuron structure & synaptic electrical-chemical transmission, reflex arc, human brain regions (forebrain, midbrain, hindbrain), plant hormones (auxin, gibberellin, cytokinin, abscisic acid), plant tropisms, and animal endocrine system.

Quick Key Takeaways:
Neuron & Synapse Transmission: Dendrite →\rightarrow Cell Body (Cyton) →\rightarrow Axon →\rightarrow Axon Terminal →\rightarrow Synaptic Cleft (neurotransmitter release across chemical synapse) →\rightarrow Next Dendrite.
Reflex Arc Pathway: Receptor (sensory organ) →\rightarrow Sensory Neuron →\rightarrow Spinal Cord (Relay Neuron) →\rightarrow Motor Neuron →\rightarrow Effector (muscle/gland). Bypasses conscious brain processing for instant protective reaction.
Human Brain Architecture: (1) Forebrain (Cerebrum): Center for intelligence, memory, voluntary actions, conscious sensation; (2) Midbrain: Auditory and visual reflex centers; (3) Hindbrain: Cerebellum (posture, balance, precision), Pons (respiration regulation), Medulla Oblongata (involuntary vitals: blood pressure, salivation, vomiting, heartbeat).
Plant Hormones: Auxin (cell elongation, phototropism bending toward light), Gibberellin (stem growth), Cytokinin (cell division, stomata opening), Abscisic Acid (ABA - stress hormone, wilting of leaves, dormancy).
Jump to Concept:1. 1. Neuron Structure, Synaptic Transmission & Reflex Arc Pathways2. 2. Human Brain, Plant Tropisms & Endocrine Hormone Regulation3. 3. High-Yield Solved Board Examination Questions (3-Mark & 5-Mark)4. 4. Practical Laboratory & Competency-Based Case Drill: Phototropism & Unilateral Light Shoot Bending (NCERT Activity 7.2)5. 5. CBSE Examiner Marking Scheme, Scientific Notation & Deduction Traps
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1. Neuron Structure, Synaptic Transmission & Reflex Arc Pathways

Fundamental Principles

Core scientific laws, chemical equations, anatomical structures, and visual model for Control and Coordination.

• Neuron Architecture & Synapse Mechanics
•
Structural Parts of Neuron:
- Dendrites: Branching projections that detect environmental stimuli and generate electrical impulse.
- Cell Body (Cyton): Contains nucleus and cytoplasm; processes incoming electrical signal.
- Axon: Long single fiber that transmits nerve impulse away from cell body to nerve endings.
- Myelin Sheath: Insulating fatty layer for rapid saltatory conduction.
•
Synaptic Transmission (Chemical Neurotransmitters):
- The microscopic gap between the axon terminal of one neuron and the dendrite of the next is the Synapse.
- When an electrical impulse reaches the axon ending, it triggers the release of chemical neurotransmitters (e.g. Acetylcholine).
- These chemicals diffuse across the synaptic gap and bind to specific receptors on the next dendrite, initiating a new electrical impulse.
📊 Control & Coordination: Synapse Transmission & Reflex ArcVisual Model
RECEPTORSkin (Heat /Pain Stimulus)SENSORYNeuron carriesimpulse to CNSSPINAL CORDRelay Neuron(Instant processing)MOTORNeuron carriesinstructionEFFECTORMuscleWithdrawsSynapse: Dendrite → Cyton (Cell Body) → Axon → Nerve Ending → Chemical Neurotransmitter across Synapse

Visual schematic mapping the neuron structure, synaptic chemical diffusion, the reflex arc spinal circuit, and the 3 brain regions.

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2. Human Brain, Plant Tropisms & Endocrine Hormone Regulation

Mechanisms & Experiments

Step-by-step chemical reaction mechanisms, experimental activities, and physiological pathways for Control and Coordination.

• Brain Regions & Endocrine Glands Breakdown
•
Human Brain (Protected by Cranium & Cerebrospinal Fluid):
- Cerebrum (Forebrain): Highest thinking center; reasoning, sensory interpretation, voluntary motor commands.
- Cerebellum (Hindbrain): Coordinates voluntary muscle movements, maintaining posture, balance, and precision (e.g. walking a straight line, riding a bicycle).
- Medulla (Hindbrain): Controls involuntary vital functions like heartbeat, respiration, blood pressure, coughing, and swallowing.
•
Plant Tropic Movements (Directional Growth Responses):
- Phototropism: Growth toward light (stem bends toward light due to Auxin accumulating on shady side, causing cells there to elongate faster).
- Geotropism: Root grows downward (+ve geotropism); stem grows upward (-ve geotropism).
- Hydrotropism: Root grows toward water; Thigmotropism: Tendrils coil around physical supports.
•
Human Endocrine System:
- Pituitary Gland (Master Gland): Growth Hormone (GH\text{GH} - deficiency causes dwarfism; excess causes gigantism).
- Thyroid Gland: Thyroxine (regulates carbohydrate/fat metabolism; requires Iodine; deficiency causes Goitre).
- Pancreas: Insulin (lowers blood glucose; deficiency causes Diabetes mellitus).
- Adrenal Glands: Adrenaline (Emergency / 'Fight or Flight' hormone - increases heart rate, breathing rate, blood supply to skeletal muscles).
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3. High-Yield Solved Board Examination Questions (3-Mark & 5-Mark)

Solved Board Questions

Standard CBSE board exam questions with complete scientific justifications and marking scheme step protocols.

• 3-Mark Standard Board Question: Trace the sequence of events that occur when a bright light is suddenly focused on your eyes. Name the pathway involved.
•
Name of Pathway: Reflex Arc (Pupillary Light Reflex).
•
Step-by-Step Sequence of Events:
1. Stimulus: Intense bright light strikes the retina of the eye.
2. Receptor: Photoreceptors in the retina detect the bright light stimulus.
3. Sensory Neuron: Transmits electrical impulse from retina to the midbrain/central nervous system.
4. Relay Neuron (CNS): Processes the sensory signal and generates an immediate motor response.
5. Motor Neuron: Transmits the motor nerve impulse to the effector muscle.
6. Effector: Iris circular sphincter muscles contract.
7. Response: The pupil constricts immediately, reducing the amount of light entering the eye to protect retinal cells from photo-damage.
• 5-Mark Comprehensive Question / Numerical: (a) What are Plant Hormones (Phytohormones)? State the specific functions of Auxin, Gibberellin, Cytokinin, and Abscisic Acid.
(b) Explain the Feedback Mechanism of hormone regulation with the example of Insulin.
•
Part (a) Plant Hormones & Functions:
- Definition: Chemical substances produced naturally in minute quantities in plant growing tips that coordinate growth, development, and environmental responses.
1. Auxin: Promotes cell elongation, apical dominance, and phototropic bending of shoot tips toward light.
2. Gibberellins: Promotes stem elongation, breaking seed dormancy, and fruit growth.
3. Cytokinins: Promotes active cell division (found in highest concentration in rapid cell-division areas like fruits and seeds), and delays leaf senescence.
4. Abscisic Acid (ABA): Growth inhibitor (Stress hormone); causes stomatal closure during drought, wilting of leaves, and seed dormancy.
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Part (b) Hormonal Feedback Mechanism (Insulin Regulation):
- The timing and amount of hormone released are strictly regulated by negative feedback mechanisms.
- When blood glucose levels rise after a meal, the β\beta-cells of the islets of Langerhans in the pancreas detect this increase and respond by secreting Insulin into the bloodstream.
- Insulin stimulates liver and muscle cells to take up glucose and convert it into stored glycogen, causing blood glucose levels to drop back to normal.
- As blood glucose levels fall back to the normal baseline, the pancreas detects the decrease and shuts off / reduces Insulin secretion.
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4. Practical Laboratory & Competency-Based Case Drill: Phototropism & Unilateral Light Shoot Bending (NCERT Activity 7.2)

Practical & Case Drill

Experimental observation analysis, chemical gas tests, and assertion-reason drills.

• Laboratory Activity Context: Phototropism & Unilateral Light Shoot Bending (NCERT Activity 7.2)
A conical flask with germinating bean seeds is placed inside an open box with light entering from only one side.
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Q1: What happens to the shoots and roots of the seedling after a few days? →\rightarrow Shoots bend toward the light source (positive phototropism); Roots bend away from the light (negative phototropism).
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Q2: Explain the hormonal mechanism causing the shoot to bend toward light. →\rightarrow Auxin is synthesized at the growing shoot tip. When light enters unilaterally from one side, auxin diffuses to the shadier side of the shoot. The higher concentration of auxin stimulates cells on the shady side to elongate more rapidly than cells on the illuminated side, causing the stem to curve toward the light.
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Q3: What would happen if the shoot tip is decapitated (cut off)? →\rightarrow Bending ceases completely because the site of auxin synthesis (apical meristem) is removed.
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5. CBSE Examiner Marking Scheme, Scientific Notation & Deduction Traps

Important Solved Board Questions

Examiner step-marking allocations, mandatory scientific terminology, and common error avoidance.

• Step-by-Step Marking Rubric & Key Terminology
•
1 Mark: Correct directional sequence of electrical impulse along neuron parts.
•
1 Mark: Accurate description of chemical neurotransmitter diffusion across synapse.
•
2 Marks: Specific roles of forebrain, midbrain, and hindbrain (cerebellum/medulla).
•
1 Mark: Explaining negative feedback loop of insulin.
• Common Error Deduction Traps
•
Trap 1: Stating that nerve impulses cross the synapse as electrical currents (they cross as chemical neurotransmitters).
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Trap 2: Confusing Cerebrum (thinking, voluntary intelligence) with Cerebellum (balance, posture, motor coordination).
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Trap 3: Stating that Abscisic Acid promotes growth (it is a growth inhibitor / stress hormone).
Authentic Board Question (3 Marks)Topic: Control and Coordination Biological Mechanisms & Physiological Pathways
Describe the anatomical structures, physiological pathways, and biological significance associated with Control and Coordination.

Official CBSE Step-by-Step Marking Breakdown:

Step 1: Biological Terminology & Organ/Enzyme Identification: Accurately name the specific biological structures, enzymes (pepsin, trypsin, lipase), hormones, or genetic alleles involved.
1 Mark
Step 2: Step-by-Step Mechanism / Pathway Flow: Describe the sequential biological pathway (circulation, filtration, reflex arc, reproduction mode, or Punnett square cross).
1 Mark
Step 3: Biological Function & Homeostatic Significance: Explain why this process is essential for organism survival, energy production, variation, or ecological balance.
1 Mark
Model Student Answer (Target: Full 3/3 Marks):
For full marks in CBSE Biology on Control and Coordination:

1. Structural Identification: Name the specific organs, cell types, or biochemical catalysts responsible for the process.
2. Physiological Process: Outline the step-by-step sequential pathway using directional flow arrows.
3. Functional Outcome: Conclude with the physiological necessity (e.g., ATP synthesis, waste removal, species survival).
Examiner Mark Deduction Traps:
•Use standard NCERT biological terminology rather than everyday descriptive language.
•In genetics questions, always show the complete parent phenotype →\to genotype →\to gametes →\to F1/F2F_1/F_2 Punnett square.

High-Frequency Conceptual Doubts & FAQs

Curated answers to the most common questions asked by Class 10 students.
A Reflex Arc is the shortest neural pathway that controls an immediate, involuntary reflex action without conscious brain processing:
Receptor (Sense Organ)⟶Sensory Neuron⟶Spinal Cord (Relay Neuron)⟶Motor Neuron⟶Effector (Muscle/Gland)\text{Receptor (Sense Organ)} \longrightarrow \text{Sensory Neuron} \longrightarrow \text{Spinal Cord (Relay Neuron)} \longrightarrow \text{Motor Neuron} \longrightarrow \text{Effector (Muscle/Gland)}

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