The brain needs a constant supply of blood to work. During a stroke, blood stops flowing to part of the brain. The affected area is damaged. Its functions are harmed or even lost. Most strokes are caused by a blockage in a blood vessel that supplies the brain. They can also occur if a blood vessel in the brain breaks open (ruptures).
The heart is a pump. It sends oxygen-rich blood out through blood vessels called arteries. Carotid arteries carry blood from the heart to the brain. Blood vessels in the brain carry oxygen-rich blood to brain tissue.
Hemorrhagic stroke occurs when a blood vessel in the brain ruptures. This lets blood spill into or build up in nearby brain tissue. The extra blood presses on those brain cells and can damage them or even cause them to die. Other brain cells die because their normal blood supply is cut off because of high pressure in the skull.