Question

Find out the correct sequence of a simple reflex arc :

• A. Brain-spinal cord-nerves-effector
• B. Effector-CNS-sensory nerves-receptor
• C. Muscles-spinal cord-brain-receptor
• D. Receptor-sensory nerves-CNS-effector

Answer 1

The correct option is D Receptor-sensory nerves-CNS-effector

The entire pathway from sensory receptor to sensory neuron to spinal cord (having interneurons) to motor neuron to effectors is called the reflex pathway or reflex arc.

Hence, the reflex pathway comprises at least one afferent neuron (coming from receptor) and one efferent neuron (going to effector or exciter) appropriately arranged in a series.

When a receptor is stimulated, it sends a signal to the central nervous system, where the brain coordinates the response. But sometimes a very quick response is needed, one that does not need the involvement of the brain. This is called as the reflex action. In a simple reflex action:

Stimulus -> Receptor -> Sensory neuron -> Relay Neuron -> Motor neuron -> Effector (Muscle).

So, the correct answer is 'Receptors - Sensory neuron - Spinal cord - Motor neuron - Muscle'

So, correct sequence of a simple reflex are: – Receptor - sensory nerves - CNS – effector