What Happens in Reflex Actions
Reflex action is a type of very quick response to a stimulus in which delay can be harmful. It eliminates the thinking and analytical component of the brain for its activity. Reflex action is found in most animals even where neuron networks have not come into existence. It persists in advanced animals because of its usefulness. Even here, the infants possess more reflex action than the adults. The total number is about 200.
Reflex action was studied for the first time by Marshals Hall (1833). It has a very short pathway from receptor organs to central nervous system to effector organ. Consultation by brain is not carried out though brain is often informed after the reflex action is over. The short circuit pathway undertaken by reflex action is called reflex arc. It consists of
- Receptor. It is sensory cell, tissue or organ which is specialised to pick up the stimulus and gets sensitized.
- Sensory or Afferent Neuron. The sensitized receptor activates and causes the development of an impulse in the sensory or afferent neuron. The impulse travels along the sensory neuron and reaches the central nervous organ.
- Part of Central Nervous System. It is spinal cord for reflex actions of trunk and limbs. For head region the brain is used as part of the reflex arc, of course without involving its thinking part. In the central nervous system the impulse brought by sensory neuron is transferred to a connector or interneuron. The interneuron passes the information to a nearby motor neuron.
- Motor or Efferent Neuron. The sensitized motor neuron carries the impulse to a specific effector organ through its axon terminal.
- Effector Organ. It is a muscle, gland, organ or tissue that on activation by the motor end plate provides a suitable response to the stimulus.
What is Importance of Reflex Action
- Control. Reflex action controls a number of activities of the body.
- Quick Response. Response to a stimulus is almost immediate.
- Accuracy. The response is accurate, useful and purposeful.
- Survival Value. Reflex action has a survival value.
- Overtaxing of Brain. Reflex action avoids overtaxing of brain.
- Coordination. It coordinates many activities of the body.
- Conditioned Reflexes. They help us to perform many of our activities like reading, writting, cycling, typing, tying laces, etc.