Circulatory and Nervous Systems: Part 2

As shown above in the video, a stroke may occur when there is insufficient blood flow to the brain. What we have found out in the previous thread is that, its not the blood that the brain necessarily needs, its the oxygen that it carries. So when blood flow is blocked, so too is the incoming oxygen. As stated there are three different kinds of strokes:

• Ischemic: One of which is an embolic stroke where a blood clot (called an embolus) forms anywhere in the circulatory system then travels up to the brain and causes damage when it reaches a vessel that is too small to travel though thus creating a blockage. The second being a thrombotic stroke, where due to a disease called atherosclerosis (fatty) plaque can build up in the blood vessels and block any thoroughfare for oxygenated blood, OR the plaque breaks off from the vessel wall and travels elseware (again usually the brain) and forms another blocked entrance.

• Haemorrhagic: One type can be a intra-cerebral haemorrhage where a blood vessel in the brain bursts and blood is leaked into the brain tissue and can cause further damage while pressure in the tightly spaced skull cavity forces the blood to spread to other areas causing more damage. The second kind is a sub-arachnoid haemorrhage where a weakness in the blood vessel forms a weak bubble (aneurysm) in the vessel wall which again may burst and contaminate the brain fluid causing damage.

The point of the ischemic stroke is that oxygen is blocked to the brain. Therefore where ever in the brain oxygen is blocked to, that part will be damaged. Or as related to a haemorrhagic stroke blood is a contaminate to brain/spinal fluid or a agent of pressure. All four can cause immense damage. This is why the stroke is medically known as a cerebrovascular accident (CVA).