Question

Write down the following in the correct order for a simple reflex arc :​
1. impulse travels in motor fibre.​
2. impulse travels in sensory fibre. ​
3. effector organ stimulated. ​
4. impulse crosses synapse.

Answer 1

Correct order is (b) – (d) -- (a) --(c).​ ​

Following are the steps followed by the simple reflex arc:​
1. Impulse is generated at the receptors of the sensory organ on receiving a stimulus and travels to the spinal cord through sensory fibre.​
2. To pass it to the adjacent neuron, the impulse crosses the synapse through the secretion of a chemical substance called neurotransmitter and the impulse is generated in the next neuron.​
3. From the spinal cord, the impulse travels to the effector organ through motor fibre.​ 4. The response is generated to the stimulus through the effector organ.