Blood Circulation to the BrainThe brain is a unique organ in the body. The blood circulation in the brain is more complex, more regulated, and less understood than the circulation in any other tissue. The large arteries carrying blood to the brain are the internal carotids and the vertebral arteries. The condition of these arteries determines how much blood flow is available to the brain. The smaller cerebral (pial) arteries respond to changing demands from blood supply from cerebral tissues. This auto regulation tries to maintain stable cerebral blood flow even with unstable cerebral perfusion pressure. Brain circulation responds in complex ways to a large number of stimuli. Failure of autoregulation may be one of the most common sources of brain dysfunction especially in people with high blood pressure on medications.
Brain activity regulates brain circulation by controlling cardiac output and blood pressure. Emotions, especially anger, are strong events that act on the cardiovascular system; heart rate increases and blood pressure rises, often dramatically. Cognitive tasks increase blood flow and metabolic rate in the regions of the brain that process the task. Changes in localized blood flow are the basis of functional imaging studies that reveal the modules in the brain that are active during task processing.
Blood-brain barrierCerebral microvessels have a unique feature, the blood-brain barrier, which protects sensitive brain cells from disturbing elements circulating in the blood. Endothelial cells line blood vessel. Their behavior regulates permeability. In the brain, tight intercellular junctions limit endothelial permeability. A variety of chemical signals to and from endothelia cells control blood vessel transactions with glial cells and neurons. Cerebral vessels have nerves supplies -sympathetic, parasympathetic, and sensory nerve fibers. Gaseous transmitters such as nitric oxide (NO) dilate small blood vessels and participate in the regulation of blood flow.
Syncope (fainting) is an expression of reduced cerebral blood flow. Prolonged standing, emotional arousal, blood pressure drugs, cardiac arrhythmias, and autonomic nervous system failure are common causes of syncope. Blood tends to pool in the legs with prolonged standing. Muscle activity is required to pump venous blood uphill back to the heart. With reduced venous return, cardiac output drops and humans faint. A common symptom, the feeling of lightheadedness is an expression of reduced blood flow to the brain. Since cerebral arterial disease increases with age, decreasing symptoms of limited blood flow become more common such as lightheadedness, fainting, personality changes and deteriorating cognitive ability.
Some of the disturbances will be regional with selectively compromised functions. Other disturbances will be global. The use of medications to reduce blood pressure may have adverse effects because lowering blood pressure can decrease cerebral perfusion in patients with chronic vascular brain pathology; they may develop focal hypoxia and even ischemia in poorly perfused regions of their brain.
Stroke is the leading cause of disability in the U.S. and CanadaStroke is the leading cause of permanent disability in the U.S. and Canada, second leading cause of dementia and the third leading cause of adult death. Stroke is the third leading cause of death and a major source of disability in the US where 700,000 people have a stroke and 158,000 die from stroke. From 1993 to 2003, the stroke death rate fell 18.5%, but the actual number of stroke deaths declined only 0.7%, according to 2006 statistics.
The main event of a heart attack is the occlusion by a sudden blood clot of one or more blood vessels supplying the heart muscle. A similar occlusion of blood vessels supplying the brain will result in the death of brain tissue or cerebral infarction. Another cause of stroke is hemorrhage from a ruptured blood vessel. Yet another stroke mechanism is the occlusion of a brain artery by a clot that traveled to the brain from another body location, usually the heart; embolism is most likely to occur in people with atrial fibrillation and mechanical heart valves.
Neurologists say doctors and the public should give stroke victims the same urgent treatment given to heart attack victims. The clot-dissolving drug TPA (tissue plasminogen activator), when used in the first three hours after a stroke, can restore blood flow in the brains of some patients. Some hospitals have better tools for dealing with strokes, but require the stroke patient to seek treatment quickly. The message in the media is to act fast on the warning signs of a stroke - stokes are now described as "brain attacks" to encourage the same sense of urgency attributed to heart attacks. Symptoms include weakness or numbness, especially on one side of the body; blurred vision, usually in one eye; slurred speech; dizziness; and explosive headache.
The hope for dramatic rescue of stroke victims with TPA is somewhat tarnished by the impractical requirement of getting the right treatment right away. One major problem is that some strokes are caused by bleeding into the brain and TPA would make this worse. Before getting TPA, patients must be checked to ensure they are not bleeding in the brain. If you were planning to have a stroke, you have to set up an ideal circumstance in order to be rescued. You would have to recognize that you were having a stroke almost immediately; you would have to get to a well-equipped hospital promptly; the emergency room would have to be set up to make the diagnosis promptly, get a high quality CAT scan done and interpreted by an expert and then you would have to satisfy several criteria for treatment - the first is that the CAT scan shows that there is no bleeding associated with the stroke symptoms.
Preventing StrokesWe share the conviction with a growing number of experts in the field that simple, safe home remedies especially diet revision and exercise can substantially reduce this destructive disease and save untold suffering and billions of health-care dollars. Smoking must stop. Diabetes, high blood pressure, and high blood cholesterol must be controlled to prevent stroke and, again, diet revision with weight loss and increased daily exercise can work wonders. Drugs are only required if risk factors are not controlled by changes in diet and lifestyle.
Well-known risk factors are
- high blood pressure
- high alcohol intake
- excess body fat
- physical inactivity.
- Diet Revision -- Alpha Nutrition Program
- Exercise and Weight Loss
- Reduce blood pressure