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 rate increases when you exercise. Photo Credit Jupiterimages/Stockbyte/Getty Images. Your heart rate increases when you exercise, because you are working harder. How much your heart rate increases depends on the intensity of your exercise and how fit you are. Exercise experts differ on how high your heart rate should be during exercise, but they agree that it needs to be substantially higher than your resting heart rate to improve your cardiovascular fitness.