How does the heart affect the brain?
The major way the heart affects the brain is through the amount of blood flow.
According to Love and Webb,1992, the brain uses approximately twenty percent of the body's blood and needs twenty-five percent of the body's oxygen supply to function optimally.
Blood flow in a healthy person is 54 milliliters per 1000 grams of brain weight per minute.
Lower heart rate will reduce this flow and can cause dizziness or even lack of consciousness.
Blood flow to the brain is so important that there is a connection between the two internal carotid arteries. It is called the Circle Of Willis.
A more serious view: