Andy Stillwell, age 10, of Let Bridge, Alberta, Canada, for his question:

What causes the pulse beat?

When a nurse takes your pulse, usually she feels the throbbing beat in your wrist. Actually you can feel the same pulsing beat in your neck and in other places where big blood vessels come near the surface. The pulse is the heart beat that pushes the bloodstream around throughout the entire body. Miles and miles of large and small blood vessels form a network    and the beating heart keeps the bloodstream flowing around and around the system.

Normally, the heart beats about 70 times a minute. Each beat pumps a squirt of oxygen rich blood into an artery that connects with the network of blood vessels. Each pulse helps to push all the circulating blood around the entire network. This is what you feel when you touch an area where a large blood vessel pulses just below the skin. The pulse is a sort of echo of the beating heart.