Generally, detectors ( sense organs) pick information from stimuli and pass it to the central nervous system through sensory neurons.
CNS sends impulses to effectors through motor neurons after processing the information received from detectors.
Picking up information from a stimulus to produce a response involves a pathway from detectors to the brain or spinal cord or a set of nerve cell heads near the spinal cord to effectors.
A reflex action is a single pathway going up to the spinal cord from detectors and returning to effectors.
Example:
For example, if you accidentally touch a sharp object with your feet, several such pathways would cause the leg muscles to remove the feet.
Mechanism of Reflex Action:
Sensory neurons send electrical impulses to a relay neuron (interneuron) present in the spinal cord.
Relay neurons connect sensory neurons with motor neurons. Motor neurons send information to the effector's muscles. Finally, a muscle contact response is generated.
Reflex actions save us from critical situations. In these actions, the brain is not affected.
Advantages of Reflex Action
Reflex actions avoid accidents. This creates less pain.