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Did you know?

The familiar sounds of your heart are made by the heart's valves as they open and close.

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A seasonal flu vaccine is the best way to reduce the chances you will get seasonal influenza and spread it to others.

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Of the estimated 2 million heroin users in the United States, 600,000–800,000 are considered hardcore addicts. Heroin addiction is considered to be one of the hardest addictions to recover from.

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Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.

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There can actually be a 25-hour time difference between certain locations in the world. The International Date Line passes between the islands of Samoa and American Samoa. It is not a straight line, but "zig-zags" around various island chains. Therefore, Samoa and nearby islands have one date, while American Samoa and nearby islands are one day behind. Daylight saving time is used in some islands, but not in others—further shifting the hours out of sync with natural time.

Neuron (nerve cell) structure. Neuron (nerve cell) structure.
feet feet
SSRIs block the reuptake of serotonin into nerve terminals, resulting in increased serotonin levels. SSRIs block the reuptake of serotonin into nerve terminals, resulting in increased serotonin levels.
Leg pull. Grasp both feet behind the heels, and gently pull legs straight toward you several inches ... Leg pull. Grasp both feet behind the heels, and gently pull legs straight toward you several inches ...
Nerve Nerve
Branches of a Spinal Nerve Branches of a Spinal Nerve
Video: Stimulus (introduction)

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