What is a reflex arc? Explain it with a labelled diagram.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Define. A reflex action is a quick, automatic response to a stimulus, controlled by the spinal cord. Its pathway is the reflex arc.
2 · Draw the reflex arc. [Diagram: skin receptor, sensory neuron with dorsal root ganglion, T.S. of spinal cord with relay neuron, motor neuron through the ventral root, muscle as effector, arrows]
3 · Name the five parts.
Receptor: skin detects heat or pain.
Sensory neuron: carries the impulse to the spinal cord.
Relay neuron: in the grey matter of the spinal cord.
Motor neuron: carries the order out.
Effector: the muscle contracts.
4 · Give the example. Touching a hot tava: the hand is pulled back at once, and the pain is felt a moment later.
5 · Importance. Reflexes are fast and protect the body from harm.
6 · Link to daily life. Hot oil from a kadai makes your hand jerk back; doctors test the knee jerk.
7 · Close. So a reflex arc lets the spinal cord protect us without waiting for the brain.
Scoring tip: Put arrows on every neuron in the diagram. Many students lose a mark for showing no direction.
