If you follow football, hockey, soccer, or boxing, then you know that athletes in these and other contact sports are at constant risk for a concussion. Every season several football players miss a number of games after absorbing vicious blows to the head.

　　Blow To The Head

　　A concussion is a blow to the head that can result in temporary confusion, amnesia, nausea, dizziness, blurred vision, and loss of consciousness.

　　Although a single concussion does not appear to result in structural brain damage or swelling of the brain, repeated concussions can cause both.

　　What Causes A Concussion?

　　Concussions are caused in one of two ways: either by the head hitting a hard surface, or by the head spinning suddenly. Take, for example, a common incident during a football game. The quarterback is hit, falls backwards, and bangs his head on the turf.

　　Although his skull stops suddenly upon impact, his brain, floating in cerebral fluid, keeps moving and hits the skull. Similarly, when a boxer gets hit in the head with a right hook, his head twists violently. The skull stops moving, but the brain keeps shaking for a few moments and may brush the skull.

　　Chemical Imbalance

　　The result is a chemical imbalance in the brain. All the neurotransmitters in the damaged area fire simultaneously, causing an overload of chemicals that impair receptors involved in learning and memory. The flood of chemicals also constricts arteries, making it difficult for the damaged cells to get the nutrients they need to recover.

　　Because the brain can take as long as several weeks to recover from a concussion, it’s a good idea to take a break from contact sports if you’ve had one.

　　什么是脑震荡？

　　如果你喜欢橄榄球、橄榄球、足球或是拳击运动，那么你就会很清楚这些以及其他接触性运动中的运动员常处于脑震荡的危险境地。每个赛季都有数名橄榄球运动员由于头部遭受剧烈冲击而缺席接下来的一系列赛事。

　　头部撞击

　　脑震荡是头部受到撞击而导致的，可能造成暂时性思维混乱，失忆，呕吐，眩晕，视觉模糊以及失去意识。

　　尽管一次脑震荡不会导致大脑结构性损伤或导致脑水肿，但是数次脑震荡可能引起上述两种情况同时出现。

　　造成脑震荡的原因

　　造成脑震荡的原因不外乎是这两种中的一种：头部撞到硬物，或者头部突然旋转。以橄榄球赛比较普遍的事件为例，四分卫触地得分，朝后方倒下，其头部就会猛烈撞击到草坪上。

　　尽管他的头骨在受到冲击时瞬间会保持不动，但是他大脑内的脑脊液仍然在晃动并不断撞击头骨。同样的，当一名拳击手头部受到一记右勾拳时，他的脑袋瞬间剧烈扭转。头骨停止移动，但是脑浆却还会震动一会儿，并有可能摩擦到头骨。

　　化学失衡

　　结果是脑部化学失衡。所有受损区域的神经传递素同时作用，造成脑内化学物质超负荷运转，从而损坏学习与记忆的神经元。化学物质过多也会引起动脉收缩，导致大脑受损细胞难以吸收到利于复原的营养物质。

　　由于脑部需要长达数周的时间来恢复脑震荡带来的损伤，如果你脑部受到撞击最好还是休息一段时间再继续参加此类接触性运动。