Just think about this idea for one minute you are earning a computer on your shoulders that is unimaginably more intricate than anything described in the wildest flights of fancy of even the most visionary fiction writer. The brain is so complex that modern neurologists feel totally overwhelmed; they feel the same awe as modem astronomers who look into space and realize how little they know about the outside universe; they feel like the man who tries to empty the water from the sea with a small cup. Such is the incredible nature and complexity of the brain, and each of us has one of these instruments. Few people, sad to say, use it very constructively. This organ is the instrument through which we can express the vast untapped knowledge of the mind. Yet few people ever use their brain efficiently in this way. Instead, the brain is treated in the same manner as a child would play with the latest electronic computing equipment. The potential that each person has in the mind is rarely expressed in the outside world.
Let us give a few awe inspiring facts. It is said that each square millimetre of the brain contains about fifty thousand nerve cells (neurons). This may not sound much, but it means that the entire human brain is composed of an estimated ten to thirteen thousand million neurons. Each of these neurons is connected directly to thousands of other neurons. The number of interconnections that result from this is enough to stagger even a mathematician or an astronomer, who is accustomed to large numbers.
Messages between neurons in the brain and nerve cells throughout the whole body, are transmitted both electrically and chemically. Neurons have bulbous endings (called synapses) which secrete chemicals that cross the microscopic gaps between individual cells and cause neighbouring cells to release their own chemicals in response. This process allows the transmission of current from one cell to another. The speed at which these cells can carry out their chemical transactions is amazing. Some of these chemical reactions occur in as little as one millionth of a second. As many as one hundred thousand neurons may be involved in transmitting simple data from the senses to the brain. Consider an example of a pin stuck in the thumb; this results in pain, followed by a yell and a rapid removal of the pin. The whole process occurs in less than one second. Numerous similar processes are occurring within the brain at this very moment.
The brain continuously functions throughout all its parts. This means that millions of neurons are in a state of excitability at any one moment. It is no wonder that the brain requires a vast amount of energy. The transportation of this energy to the brain depends on an efficient blood supply. Sirshasana greatly improves this blood supply. It is therefore no surprise to discover that sirshasana has been found to significantly improve its efficiency.
The brain is a constantly changing pattern of nerve impulses that performs millions of computations simultaneously. It is said that it constantly receives and analyzes approximately two million visual input data (through the two million nerve connections to the eyes) and about one hundred thousand sound inputs (from the one hundred thousand nerve connections to the ears). Besides this, the brain is continuously receiving and processing millions of nerve impulses from other parts of the body. All this is happening in your head.