Which is the correct sequence of the components of a reflex arc?
(a) Receptors Muscles
Sensory neuron
Motor neuron
Spinal cord
(b) Receptors Motor neuron
Spinal cord
Sensory neuron
Muscle
(c) Receptors Spinal cord
Sensory neuron
Motor neuron
Muscle
(d) Receptors Sensory neuron
Spinal cord
Motor neuron
Muscle
Explanation:
The reflex arc is a neural pathway that controls a reflex. The reflex arc is a part of the PNS and is responsible for actions performed in response to certain stimuli, such as pulling a hand away from a hot object. It consists of 5 components- a receptor that receives the initial stimulus, such as skin, muscles or organs, a sensory neuron that carries the signal to the central nervous system (the spinal cord), an interneuron that relays the information to the central nervous system, and one or more motor neurons that relay the information to the final component of the arc, the effector. The effector could be a muscle, a gland or both. Hence, (d) is the correct option.