2023 · Q59
Reflex arcs are evolved in animals for quick and efficient responses. Which one of the following sequences correctly represents a reflex arc?
General KnowledgeBiology
- AReceptor-Sensory neuron-Relay neuron in spinal cord-Brain-Motor neuron-Effector
- BReceptor-Sensory neuron-Brain-Relay neuron in spinal cord-Motor neuron-Effector
- CReceptor-Motor neuron-Relay neuron in spinal cord-Senosry neuron-Effector
- DReceptor-Motor neuron-Brain-Sensory neuron-Effector
Explanation
Cross-checked against the abhipedia CDS 2023-1 solution: the intended sequence is Receptor -> Sensory neuron -> Relay neuron in the spinal cord -> Motor neuron -> Effector. The impulse travels from the receptor along the sensory neuron to the spinal cord, where the relay (association) neuron passes it to the motor neuron, which carries the response to the effector (muscle/gland) — this spinal route is what makes the reflex rapid and involuntary, without requiring the brain. Option A is the only sequence preserving this order.