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pressure are known as arteries and arterioles. These vessels connect to narrow vessels called capillaries. The capillaries, of which there are a great number, reduce the pressure of the blood. Capillaries are also the blood vessels that connect the different parts of the brain to each other. After traveling through the capillaries, the blood--with far less oxygen and under far less pressure--is transported back to the heart by the veins and venules.
Another important part of the brain is the part that makes, stores temporarily, and circulates the cerebrospinal fluid. The cerebrospinal fluid bathes the brain almost as if it were floating in a swimming pool. This cerebrospinal fluid not only circulates around the brain and spinal cord, but is also located inside the brain in important structures called the ventricles and cisterns.
WHEN TRAUMA OCCURS
Brain trauma is a wound or shock that occurs because of a fall, crash, or some other event. Sometimes masses not usually present within the brain are formed as a result of trauma. When these additional masses--such as a blood dot or hematoma (i.e., blood that is no longer flowing in the blood vessels) or swelling (i.e., excess fluid in the tissue)--develop inside the skull, then the pressure within the skull (or cranium) increases (intracranial pressure).
Initially the brain has the ability to adjust to small increases in pressure inside the skull or cranium.
If additional masses develop within the skull, the brain responds by shrinking the size of the blood vessels and therefore decreasing the amount of blood volume. Although this decreases the overall amount of the blood, it can also decrease the blood that is needed for the brain to function. Blood flow is so important to the brain that approximately 20% of the entire output of the heart goes there.
Another way that skull (or intracranial) pressure can be decreased is by shrinking the size of the compartments (ventricles and cisterns) where the cerebrospinal fluid is circulated or stored. These areas shrink in size, allowing room for the expansion of the swollen brain or increasing blood clot.
These are the ways that the brain initially responds to an increase in intracranial pressure. After the excess fluid and normal circulating blood is decreased within the skull in order to decrease intracranial pressure, the only thing left that can be somehow altered or moved is the brain itself. A hole exists at the base of the skull, approximately the size of a silver dollar. When the pressure inside the skull can no longer be accommodated through the ways just described, all of the brain starts to move through this hole--a process known as herniation. If the brain--a large object--is forced to move through this very small hole, the brain will suffer irreversible damage.
THE AFTER EFFECT OF BRAIN TRAUMA
SECONDARY INJURIES
When the brain and skull are shaken-- such as in a sudden stop from a motor vehicle crash or from a fall--the connections within the brain itself may be torn.
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