Reflex action is a rapid automatic and involuntary response to a
stimulus which is not under the control of the brain. If we
unknowingly touch a hot object, we immediately move our hand
away from it. So moving our hand away on touching a hot plate is
an example of reflex action. A knee jerk, coughing, yawning,
blinking of eyes, sneezing, salivation, movement of diaphragm
during breathing are all examples of reflex actions. The nerve
pathway involved in a reflex action is called a reflex arc. If
we unknowingly touch a hot object, this heat is sensed by a heat
receptor (Thermo receptor) in our hand. The receptor starts an
impulse in a sensory neuron, which transmits the message to the
spinal cord. The impulse is passed to the relay neuron, which is
in turn passes to motor neuron. The motor neuron passes the
impulse to a muscle in our arm. The muscle of arm is an effector
organ because it responds to the stimulus. Stimulus → Receptor →
Sensory neurons Effector organs ← motor neurons ← spinal cord
Dear students t