What is a stroke?
A stroke occurs when a blood vessel bringing blood and oxygen to the brain is interrupted or ruptures (bursts) and brain cells don’t get the flow of blood that they need. Deprived of oxygen, nerve cells can’t function and die within minutes. When nerve cells do not function, the part of the body they control can’t function either. The devastating effects of stroke are often permanent because dead brain cells can’t be replaced.
Blood supply to the brain
Blood vessels that carry blood to the brain from the heart are called arteries. The brain needs a constant supply of blood, which carries the oxygen and nutrients it needs to function. Each artery supplies blood to specific areas of the brain. A stroke occurs when one of these arteries to the brain either is blocked or bursts. As a result, part of the brain does not get the blood it needs, so it starts to die.
Motor and sensory function
The human brain is divided into several areas that control movement and sensory function, or how the body moves and feels. When a stroke damages a certain part of the brain that area may no longer work as well as it did before the stroke. This can cause problems with walking, speaking, seeing or feeling.
Left and right hemispheres
The left side, or hemisphere, of the brain controls how the opposite (right side) of the body moves and feels, and is responsible for how well we can figure out problems with science, understanding what we read and what we hear people say, number skills such as adding and subtracting, and reasoning. The right side of the brain controls the movements and feelings on the left side of the body and is in charge of how artistic we are, including musical and creative talents.
Mechanism of normal and blocked artery blood flow
Normal artery – Blood flows easily through a clear artery.
Blockage – An artery can become blocked by plaque (a fatty substance that clogs the artery) or a blood clot, which reduces blood flow to the brain and may cause a stroke. In this picture, atherosclerosis (ath”er-o-skleh-RO’sis), a hardening of the arteries, is caused by cholesterol or plaque build-up.
Blockage cleared – The plaque or blood clot breaks up quickly and blood flow is restored to the brain. This may happen during a TIA or mini-stroke, where brain cells recover with no permanent brain damage.