Pranayama - physiology

Breath is the source of life, changing with stress levels. When confronted with danger, our breathing becomes rapid and shallow to increase oxygen content. In normal circumstances, blood supply balances around the body, supplying oxygen rich blood to all organs rejuvenating tissues and supporting oxidation process within the body.

We breathe without noticing it. It is an involuntary action, something that is done without being conscious, as a reflex action. During breathing-in, we expand the chest so that the lungs admit air from the atmosphere. The diaphragm which forms the base of the thoracic cavity contracts and moves downward. This causes negative pressure within the lungs, leading to air being drawn through the mouth and nostrils into the wind pipe ultimately reaching the lungs. The downward movement of the diaphragm during inhalation causes expansion of the chest as the lungs fill out against the rib cage. In exhalation, the abdominal muscles contract, squeezing the abdominal viscera against the liver, stomach and diaphragm. The diaphragm relaxes and as it is pushed up, the lungs get compressed, forcing air, now filled with carbon dioxide and water vapour out.

In normal, sedentary breathing, the lungs are not completely filled or emptied in each respiratory cycle. We normally take in and force out about 500 ml. of air in each cycle. After such a normal exhalation we can force out a further quantity of one litre of air. The lungs are not fully emptied even at this stage and still hold about 1200 ml. of air called residual volume that cannot be forced out of the lungs. The maximum volume of air that can be taken in is called aspiratory capacity and this is about 3500 ml. After such an inhalation the lungs hold nearly five litres of air, called total lung capacity. The maximum amount of air that a person can draw out after taking a deep breath is called the vital capacity and it gives information about the strength of the respiratory muscles, the ability of the lungs and the size of the thoracic cage.

Atmospheric air entering the lungs contains roughly 79% nitrogen, 20% oxygen, and traces of carbon dioxide. Out of these only oxygen is used by the body. In exchange, the body gives up carbon dioxide and water vapour. The lungs provide a vast area for this gaseous exchange. The wind pipe (trachea) divides into two bronchi. Each bronchus enters the lung on its side and divides itself into several branches called bronchioles. The bronchioles further divide and sub-divide themselves into fine terminal branches, which end into respiratory bronchioles that hold minute air sacks called alveoli. Alveoli have a very thin lining surrounded by thin walled capillaries that facilitate exchange of gases. Though each alveolus is a very small microscopic structure, the number of alveoli in the lungs is enormous, providing an area of almost 50 square meters for exchange of gases.

The process of exchange of gases in the alveoli to and from the blood surrounding it is called diffusion. Oxygen moves from the air to the blood and is absorbed by the hemoglobin in the blood while carbon dioxide and water vapor diffuse from the blood to the alveolar air.

Absorption of oxygen and elimination of carbon dioxide and water vapor is the essence of respiration. This process goes on continuously in us as long as we live, without requiring our attention. The body changes various elements of respiration to suit the needs of the body. These changes are governed by the nervous system.

Why do we breathe? Every living tissue and cell requires a constant supply of energy to live. This energy is stored in the molecules of substances such as glucose, fructose, fatty acids, and amino acids which are the end products of the process of digestion of food which we eat. These are released by the body through a process called oxidation that uses oxygen. In the absence of oxygen the process of release of energy comes to a halt, and results in the death of that tissue.

It will be observed that in any fight/flight situation, such as while taking a long or high jump, or lifting a heavy weight etc., we automatically stop the breath. Breathing is also arrested when there is a sudden shock and when there is complete absorption of the mind in something interesting. This comes because of intensity of focus. Also, while we are resting, breathing automatically slows down, whereas, when there is physical activity necessitating an increased supply of oxygen and the faster removal of carbon dioxide, breathing automatically becomes faster and deeper. Therefore, there is a definite linkage between breathing and the psychosomatic functioning of the body.

Disciplining the breathing process means increased absorption of oxygen & greater efficiency of the lungs.

Share your opinion and experiences

Ø  Do you practice any form of aerobic breathing?

Ø  What is your experience?

Ø  What are the preparations you make before starting exercises?

Ø  What are the benefits you have experienced?

Ø  Comment on breathing and health.

Ø  Breathing and balanced thinking.

Ø  What changes to your breathing have you have observed when you are stressed.