Strokes The human brain is the command center for the human nervous system. It receives input signals from the sensory organs and sends output signals to the muscles. The brain is the largest of all vertebrates and has the same basic structures as other mammals. It weighs 3.3 pounds and makes up about 2% of the human body weight. The human brain contains about 86 billion nerve cells called neurons defined as the “gray matter”, it also contains nerves fibers called the “white matter.” About 800,000 people experience a new or recurrent stoke. What is a stroke? A stroke is a brain attack that happens when blood flow to the brain is cut off. When this occurs brain cells are deprived of oxygen and begin to die. Brain cells die during a stroke
