However, they are absorbed, usually as methyl mercury, by algae at the start of the food chain. This algae is then eaten by fish and other organisms higher in the food chain. Fish efficiently absorb methyl mercury, but excrete it very slowly. Methyl mercury is not soluble and therefore not excreted.
For example, a 10- to 15-minute brisk walk typically elevates the heart rate to 110 to 120 beats per minute. Also, the sinus node increases the heart rate when the body is stressed because of illness. In all of these circumstances, the heart rate increase is a normal response. Likewise, the sinus node signals the heart to slow down during rest or relaxation.
A normal heart rate-about 60 to 100 beats per minute. Your heart rate can increase beyond 100 beats per minute if your body needs more blood, such as during strenuous exercise. Some athletes may have normal heart rates below 60 beats per minute because their hearts are very efficient and don't need to beat as fast.