Reflex action

A voluntary action, like picking up a pen, is decided by the brain. That takes time. Most reflexes take a shortcut through the spinal cord, and the brain hears about it a moment later. The path is called the reflex arc:

• Receptor: picks up the stimulus, such as heat on the skin.
• Sensory neuron: carries the message to the spinal cord.
• Relay neuron in the spinal cord: passes it on straight away.
• Motor neuron: carries the order out.
• Effector: the muscle or gland that acts.

ICSE also sorts reflexes into two kinds. A natural reflex is inborn, like blinking when dust flies at your eye. An acquired reflex is learnt through practice or habit, like typing or cycling.

A small example

You touch a hot pan and pull your hand back before you feel the pain. The spinal cord sent the order to your arm muscle.

Where marks go

CBSE's 2026-27 sample paper has no question on the reflex arc. A marking scheme gives marks for each named part, so know how a sensory nerve differs from a motor nerve. Sensory means towards the spinal cord or brain. Motor means away from it, to a muscle or gland.

In ICSE, the 2027 specimen paper describes a girl whose mouth waters when the lunch bell rings. The draft marking scheme gives the answer as an acquired reflex. She has learnt to link the bell with food. The 2024 paper asked for receptor, sensory neuron, motor neuron and effector in order. CISCE's 2024 report asks teachers to stress the correct sequence.

About the author

Deepti Sardana

Founder Member & Academic Lead

An IIT alumna (M.Sc., M.Phil.) with over 25 years in teaching, child psychology and learning assessment. As Academic Lead at EduBrahma, she leads the method TRUtesting uses to find where and why a child loses marks.

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