4. What happens when your brain is injured?

There are several kinds of brain injury, including blows to the head, bleeding, and direct damage to the brain itelf, such as from a gunshot wound.

In the case of a blow to the head (such as might occur if you fall or are in a car accident), the force of the blow causes the brain to be forced against the side of the immobile skull and to swell. In addition, there may be bleeding into or around the brain. The brain swells when it is injured, just like any other part of your body swells. For example, when an ankle is injured by a sprain it becomes swollen. The difference between a swollen ankle and a swollen brain that your brain is encased in the unyielding bony skull, where there is very little room to accommodate the swelling. Once the limited extra room in your skull is used up, the brain tissue starts to push down through the opening at the bottom of the skull where the spinal cord continues down the vertebral column.

In the case of an aneurysm or stroke, a blood vessel in your head bursts or a clot stops the flow of blood and oxygen to the brain tissue. Lack of blood causes injury to the brain cells, and once again, the injured brain itself begins to swell and more brain injury occurs because the skull cannot accommodate the extra fluid.

Finally, if there is a gunshot wound (or similar wound involving a foreign object penetrating the skull), the brain is directly damaged by the bullet's tearing through the brain tissue, possibly ricocheting within the skull and causing bleeding, swelling, and further damage that way.

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