Arrange and rewrite the terms in each group in the correct order to be in a logical sequence beginning with the term that is underlined:
Effector, RECEPTOR, Motor neuron, Sensory neuron. (Begin with: Receptor)
Topic: Reflex arc
Answer
Receptor → Sensory neuron → Motor neuron → Effector
This is the REFLEX ARC, the path an impulse takes in an involuntary response: RECEPTOR — detects the stimulus (for example a pain receptor in the skin) SENSORY (afferent) NEURON — carries the impulse TO the spinal cord MOTOR (efferent) NEURON — carries the impulse AWAY to the organ that acts EFFECTOR — the muscle or gland that responds
THE WORDS THEMSELVES give the order: SENSORY relates to sensing, so it must come immediately after the receptor; MOTOR relates to movement, so it must come immediately before the effector.
A full answer would insert the RELAY (connector) NEURON in the spinal cord between the sensory and motor neurons, but it is not in the list given.
The whole point of a reflex is that the impulse is dealt with by the SPINAL CORD without waiting for the brain, which is why reflexes are so fast.