Definition: It is nerve mediated, automatic, involuntary and spontaneous response to a stimulus acting on a specific receptor without consulting the will.
It was discovered by Marshal Hall(1833)
Reflex action occurs in response to a stimulus where delay can be harmful.
Example: Wider opening of pupil in dimlight, narrowing of pupil in strong light, salivation when food is eaten, jerking of knee when hit below knee cao
Conditioned reflexes: By regular association, Habit or practice, some action can be converted into actions.
Example of conditioned reflexes: Writing, reading, walking, driving, pedalling, salivation at sight or smell of food,
It is required a stimulus, a receptor organ , sensory neurons, a part of central nervous system, motor neurons and effector organ.
The pathway taken by a stimulus to travel from receptor organ to effector organ is known as reflex arc.
1) Receptor Organ: It is a tissue or organ which receive the stimulus for initiating nerve impulse, e.g,
2)Sensory Neurons: They conduct impulses from receptor to central nervous system.
3)Part of Central Nervous system: It is spinal cord for most of the apparent reflexes that originate in the trunk and limbs of the body,
e.g , withdrawal of hand or foot on being pricked , knee jerked reaction,
Brain is also used as part of the reflex arc in some cases,
Importance of Reflex Action