Most of the functions that occur in our body are involuntary, without us being conscious of them happening. This autonomy is prevalent in almost all processes of the human body like – immunity, response, control and coordination.
We’re going to crack the code of brain, so let’s move on!

Being autonomous makes these processes biologically efficient, and beneficent for survival.
When you see a survival threat [imagine a pack of dogs running behind you], blood rushes to your limbs instead of the viscera , so that you can fight the threat, or run away from it – Who causes it ? .

You don’t have to tell yourself that I need more blood in my arteries to fight or escape. Brain automatically does it for you. Now, all this arrangement was to increase chances of our survival. Amidst this evolutionary journey, humans developed intelligence, which was followed by the advent of civilization.
In civilized world, we don’t have lions chasing us, we don’t have everyday survival threats. But our Amygdala, still senses them, still finds spooky coincidences, it finds horrific patterns and construes doomsday in random glyphs. It couldn’t adapt to this abrupt change in the environment around us. Hence biologically, it perceives house debt, college examination and divorce as a survival threat. And therefore,
There lies the stress.
People find emotional events as painful – finding them no lesser than physical injuries. This is because the brain uses exactly the same processes to perceive, understand and respond to them. That is why we have metaphors like – You broke my heart, Going weak in the knees, butterflies in the stomach (blood moving from stomach to genitals after sensing presence of a sexual prospect). Our body functions more on its own and less by us. This is a grave problem, we live in a body whose brain cares for us, but doesn’t quite understand our non-physical complexities, our expanded social being. This calls for the need of a master overwrite system.
We deconstructed our brain, and learned to control what is autonomous. Since it is about the mind, Meditation is perhaps the most badass invention of all time. A science, an art and a way of living given to us through hard-work and sacrifice of hundreds of saints over thousands of years.
Meditation and Stress
Amygdala : Amygdala is a region in the brain that is centrally involved in emotional processing and the interactions between attention and emotion.
Amygdala function is impaired in a number of disorders including depression, anxiety, and post-traumatic stress disorder.
Many studies conclusively suggest that the amygdala response to emotional stimuli is substantially lower when the subject is in a meditative state of mindful-attention. In recent studies, it has been shown that the effects persist in ordinary, non-meditative states as well, and prolonged meditation results in better control over emotions and an improved response to threats.
Stress is primarily a consequence of sympathetic nervous system. Opposite to sympathetic nervous system (fight and flight) is parasympathetic nervous system (feed and breed /rest and digest). Inward-attention meditation manages to increase parasympathetic activity, it essentially relaxes us to such an extent that the flood flows more to viscera and less to limbs, resulting in faster growth and robust immunity. Page on 113.37.243
Overactivity of Sympathetic nervous system has a direct correlation with Cardio-vascular diseases. Meanwhile, meditation has a clear effect on blood-pressure of subjects with hypertension disorders. Sympathetic Nervous System Overactivity and Its Role in the Development of Cardiovascular Disease Page on

Other Impact Areas
There are other parts of the brain that are effected by meditation. Parietal Lobe responsible for orientation in space-time shows significant drop in activity. This according to some also explains the reason for a sensation of “being one with everything” in Buddhist and Yoga monks.

Melatonin Levels increase in the sleep-times followed by meditation sessions. Melatonin is responsible for circadian rhythm (body clock). It also is the strongest agent that we have against free radicals, responsible for undesired mutations that occur in the body.
A lot of people are going through regular medical tests to confirm effectiveness of meditation. Some of them are traditional Buddhist monks and Yoga Practitioners, some of them are unconventional mavericks like Wim Hof.