If you accidentally touched a hot stove, what would you do? You would immediately jerk your had away even before you have had time to think about it. This action is called a reflex action. A reflex action is an automatic nervous action, in which a stimulus causes a rapid and totally involuntary response. In this case, the hot stove is a stimulus, and the jerk is the response.
Reflexes such as the pupil reflex are quite common. When a bright beam of light hits a person’s eye, his pupil automatically becomes smaller, i.e., it contracts. When the light is taken away and his eyes are shaded, the pupils return to their normal size. In this example, the light is the stimulus and the reaction of the pupil is the response.
Reflex actions re of two types- unconditioned ad conditioned. Unconditioned reflex actions re exemplified by the reflex tests of the physician. When a doctor tests a person’s reflexes, he makes sure that the different parts of his nervous system are functioning properly.
One reflex action frequently tested is the knee-jerk action. In this, the doctor lightly strikes an area just below the kneecap with rubber hammer. This cases the lower part of the leg to jerk upward suddenly. This is because the nerve impulses move via the spinal cord directly to the leg muscle and are not controlled by the brain.
Conditioned reflex actions are a result of particular internal or external stimuli. The Russian physiologist Ivan Pavlov and his associates popularized such conditioning process. Pavlov believed that whenever there was a response to a particular stimulus, a kind of reflex was established in the brain. However, most psychologists today believe that the mechanism of learning is much more complicated than what was explained by him.
Now the question arises- what cause a reflex action?
To explain it in simple terms, four basic processes are involved in a reflex action. These are- reception, conduction, transmission, and response. The stimulus is received by receptors nerve ending. Energy from the stimulus is changed into nerve impulses and carried from the receptor to the central nervous system. The nerve impulses are then sent to the motor nerves. The motor nerves control muscle action, causing the muscles and gland respond. Most reflex actions, however, are much complicated and also involve other parts of the nervous system, like the brain. More than 90% of all our actions are performed by our nervous system, through reflex actions.