The correct sequence of components in a reflex arc is (d) Receptors → Sensory neuron → Spinal cord → Motor neuron → Muscle.
Explanation:
Receptors: These are specialized cells that detect stimuli like light, touch, or temperature.
Sensory neuron: This neuron carries the signal from the receptor to the spinal cord.
Spinal cord: This is the central nervous system structure where the sensory neuron synapses with the motor neuron.
Motor neuron: This neuron carries the signal from the spinal cord to the muscle.
Muscle: This is the effector organ that responds to the motor neuron signal by contracting.
Why other options are incorrect:
(a) Receptors→ Muscles→ Sensory neuron→ Motor neuron→ Spinal cord: This sequence is incorrect because the sensory neuron should carry the signal to the spinal cord before the motor neuron.
(b) Receptors→ Motor neuron → Spinal cord → Sensory neuron → Muscle: This sequence is incorrect because the sensory neuron should be activated before the motor neuron.
(c) Receptors → Spinal cord → Sensory neuron → Motor neuron → Muscle: This sequence is incorrect because the sensory neuron should be connected directly to the receptor, not the spinal cord.