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.
Your heart attempts to compensate for this by increasing its output via an increase in heart rate. So, faster heart rate=higher cardiac output=more blood to the brain (a good thing). A rise of less than 20 beats per minute is considered normal (some say 25). You can also measure your blood pressure lying/standing.