Our body is a living organism which is constantly responsive to the environment, both within the body and outside it. And stress must have been part of our life from our cave dwelling age. Our ancestors must have reacted to stress in much the same ways as we do, such as loss of vigour, exhaustion after a hunt, shivers down the spine when lightning and thunder split open the skies, or hair standing on end when face to face with a woolly mammoth. Presumably, this is how the body has learned to defend itself against aggression.
When a threat signal is received, the body is prepared for action with the secretion of hormones. The muscles tense for action, the heart beats faster in order to pump more blood to the muscles, sugar pours into the bloodstream and the pupils of the eyes dilate for maximum vision. At the same time, non-essential functions like the digestion of food, are temporarily switched off. As the body prepares to protect itself, blood moves away from the skin surface, as a measure to safeguard against possible loss of blood. The sweat glands are activated to perspire, as the resultant evaporation keeps the body cool while glucose is being burnt in order to provide extra energy to the muscles.
The body's action is what is known in psychological terms as the 'fight or flight' response. It is the body's natural response to stress; and depending upon the nature of the stress and the body's own ability to cope with it, the body is ready to face the challenge and fight it, or take flight from the threat.
Irrespective of whether the threat is exaggerated or imagined, these body responses take place as if the threat is real. The response depends entirely on how the individual's brain translates the threat stimuli transmitted by the sense organs. The only manner in which we can consciously de-link the brain from the sense stimuli is through the practice of pratyahara. Pratyahara helps to develop a sense of detachment from the happenings around us, and 'insulates' the brain from an unnecessary stream of sense stimuli. In the state of pratyahara, the brain is able to function more through intuition, which is the highest form of intelligence. In our normal day-to-day activities, we do practice pratyahara unconsciously when we are not interested in an event or in a person.
The body mechanism takes mainly two types of responses, the syntoxic response and the catatoxic response. The syntoxic response stimulates tissue tranquilizers which create a state of passive tolerance to outside 'aggressors* for a peaceful coexistence with the pathogen. On the other hand, the catatoxic response produces 'missile' enzymes that attack the pathogen and destroy it, usually by accelerating its metabolic degradation.
Modern medicine has developed the concept of hetrostasis, that is the artificial raising of the homeostasis level to a superior level. This is achieved by introducing natural or artificial exogenous compounds to stimulate both syntoxic and catatoxic reactions. In an ashram environment, a state of hetrostasis is induced naturally, through yogic practices, hard work, controlled diet and a planned, stressful lifestyle.
It has been found in experiments that there is a general adaptation syndrome to stress. During continued exposure to any noxious agent, the body-system of the laboratory animal reaches a state of adaptation or resistance after the initial alarm reaction. It proves that the body system cannot be maintained in a continuous state of alarm. If the laboratory animal survives the initial exposure to the noxious agent, then its body-system reaches a state of resistance.
The body-system reacts in totally opposite manners in the alarm and resistance stages. During the alarm reaction, the adrenal cortex discharges secretory granules into the bloodstream. This depletes corticoid-containing lipid storage material When the animal's body-system reaches the stage of resistance, however, the cortex becomes rich in secretory granules. Similar contrasts take place in the production of some of the other body chemicals.
On continued exposure to the noxious agent, the animal's body-system reaches a third stage, the stage of exhaustion. Thus, the 'adaptative energy' is not limitless. Also, this energy Joss cannot be attributed to the caloric energy loss, as the food intake by the animal during the stage of resistance was normal. Yet something was 'lost' in order for exhaustion to set in. Yoga, explains it as prana or the life-force, which activates the gross body and supports and maintains life by supplying vitality to it.
The French physiologist, Claude Bernard proposed in the early nineteenth century, the concept of 'fixity of the mileu interieur which is the condition of free and independent life'. This concept was later refined to one of homeostasis. Yoga aims at maintaining the status quo in the body through the free, unobstructed flow of prana throughout the body, as any obstruction in its flow to a specific organ causes disease in it. Pranayama in hatha yoga, and prana vidya, a self-healing technique from the tantra, are practices that are based on the concept of prana.