Explain Control of Our Heart through Nerves

When we exercise in the mornings, the heart beats faster and when we sleep at night, it slows down. Have you ever wondered how does the heart tick? Our old Rishis and Saints have spent years answering this question. Some have managed to even stop their heart from beating while others have made it beat at will at a rate so fast that it would kill a normal human being. How do they manage to do that? They, over the years, have simply gained control over their autonomic nerves that supply the heart and blood vessels.