Define reflex action with suitable examples.

When we suddenly withdraw our hands on pricking a pin, it is a reflex action. This type of sudden response to a stimulus is involuntary. A reflex action is defined as an unconscious and involuntary response of effectors to a stimulus. In reflex actions, a message from the receptors is relayed by sensory nerves to the spinal cord, which sends information for response via motor nerves to effectors. The pathway is called reflex arc. The simplest type of reflex action is knee-jerk reflex. In this case, while sitting with freely hanging legs, a strike below the knee cap kicks the leg forward. Other reflex actions are coughing, sneezing, yawning and blinking of eyes.