CBSE Class 10 Science: Control & Coordination — Notes 2026

Nervous System

• Neuron: structural unit; parts: dendrites, cell body (cyton), axon, myelin sheath
• CNS (brain + spinal cord) and PNS (cranial + spinal nerves)
• Types of neurons: sensory, motor, relay/interneuron

Nerve Impulse

• Resting potential: K⁺ inside, Na⁺ outside; inside is negative (−70 mV)
• Action potential (depolarisation): Na⁺ rushes in → inside becomes positive
• Synapse: gap between neurons; neurotransmitter (acetylcholine) carries signal across

Reflex Action

• Involuntary response to stimulus; controlled by spinal cord (not brain)
• Reflex arc: receptor → sensory nerve → spinal cord → motor nerve → effector
• Examples: knee jerk, withdrawal reflex, pupil contraction in bright light

Human Brain

• Forebrain (cerebrum): thinking, memory, voluntary actions, speech, vision, hearing
• Midbrain: relay station between forebrain and hindbrain; controls eye movement
• Hindbrain: cerebellum (balance, coordination), pons (relays), medulla (breathing, heart rate)

Hormones in Animals

• Pituitary (master gland): GH, TSH, ADH, FSH, LH
• Thyroid: thyroxine (metabolism, growth); iodine deficiency → goitre
• Pancreas: insulin (lowers blood glucose) and glucagon (raises blood glucose); diabetes mellitus

Hormones in Plants (Phytohormones)

• Auxins (IAA): promote cell elongation; phototropism (auxin accumulates on shaded side)
• Gibberellins: stem elongation, seed germination, break dormancy
• Abscisic acid (ABA): dormancy, stomata closure in drought; ethylene: fruit ripening, leaf fall

CBSE Exam — Control and Coordination

• Draw and label a reflex arc
• What is the difference between nervous and endocrine control?
• Explain how auxin causes phototropism in plants