All visible and invisible happenings of the universe are under the influence of the Cosmic impulse known as Prana in the Vedas. There are five kinds of Prana in the body, and each has its region of control.
Prana, the incoming wind
Prana is situated in medulla oblongata and governs the respiratory and circulatory functions.
Its normal function is to receive all incoming impulses and to control unconsciously the activity of the sympathetic fibres.
Its region of control is between the larynx and the base of the heart, and it rules the region between mouth and heart.
It governs the verbal mechanism, vocal apparatus, movements of gullet, respiratory system and the corresponding muscles.
Apana, the downward wind
Apana dwells below the navel
It rules the actions of the kidneys, the colon, the rectum, the bladder and the genital. These functions are governed by impulses from the lumbar portion.
Normally Apana sends outgoing impulses to the excretory and ejaculatory mechanisms. These impulses cause relaxation of the sphincters of the anus and bladder, as well as contraction of the muscular portion above them. These actions are necessary for expulsion.
Samana, the balancing wind
Samana's location is in the region between the heart and the navel.
It is controlled by splanchnic nerves arising out of the ganglia in the thorax region.
It rules the machinery of metalbolism for the maintenance of life, the secretion of the stomach, the liver, the pancreas and the intestine, circulation of blood in the heart and the blood vessels. It inhibits the excessive activity of the digestive tract.
Udana, the lifting wind
rules the region above the larynx. As the thalamus is the highest reflex centre in the brain, and all impressions ascend to it, it is called Udana, the lifting wind.
All automatic functions of anatomical sections are under control of the cephalic division. It keeps us on the alert regarding our special senses.
By conscious control over udana, all outgoing and incoming sensations can be suppressed. The suppression is necessary to prevent the distraction of the mind.
Vyana, the circulating wind
Vyana pervades the whole body.
It governs the movements of the body, contraction and relaxation of the muscles (voluntary and involuntary), the joints etc.
It is responsible for the erect posture of the body, reflex action through the spinal cord and through the stimulation of the autonomic ganglia.
Its function is to keep the body in stationary condition which is due to the balancing of action of the antogonic musles through the unconscious reflexes that are generated along the spinal cord.