Reflex Action — Interactive Diagram

See how your body pulls your hand away from a hot object before you even think about it.

Reflex Action — Interactive Diagram

See how your body pulls your hand away from a hot object before you even think about it.

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TL;DR: See how your body pulls your hand away from a hot object before you even think about it.

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Reflex Action: See how your body pulls your hand away from a hot object before you even think about it.

Why it matters: The reflex arc (receptor → sensory neuron → spinal cord → motor neuron → muscle) shows how the nervous system protects us instantly — a key diagram.

Reflex Action — Step by Step

  1. STIMULUS: your hand touches a hot object. Heat RECEPTORS in the skin detect the danger.
  2. The signal races along a SENSORY NEURON to the SPINAL CORD — it does not wait to reach the brain.
  3. The spinal cord instantly sends a signal back along a MOTOR NEURON to the arm muscle — you pull your hand away. Fast and automatic!

Quick Notes — the Exam Crux

  • A reflex action is a quick, automatic response to a stimulus, not under conscious control.
  • The pathway it follows is called the reflex arc.
  • Order: receptor (skin) → sensory neuron → spinal cord (relay) → motor neuron → effector (muscle).
  • It is processed by the spinal cord, which makes it faster than a brain-routed response.
  • The brain is informed afterwards, which is why you feel the pain a moment later.
  • Examples: pulling the hand off a hot object, the knee-jerk, blinking, sneezing.

Remember It (Memory Trick)

Reflex arc: Receptor → Sensory neuron → Spinal cord → Motor neuron → Muscle. The brain is bypassed for speed — "the spinal cord decides, the brain finds out later."

Real-Life Example

Touch a hot tawa by accident and your hand jerks back before you even feel the pain — the spinal cord fires the response instantly to protect you.

Test Yourself

Which part of the nervous system controls a reflex action?

The spinal cord.

Why is a reflex action faster than a normal voluntary action?

It is processed directly by the spinal cord, bypassing the brain.

Write the correct order of a reflex arc.

Receptor → sensory neuron → spinal cord → motor neuron → effector (muscle).

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