Question: why does our heart stop beating

Robert Lees answered on 16 Nov 2015:

The heart is made up of A LOT of muscle, it works constantly to pump blood around the body. Muscle cells require oxygen to get the energy to contract (squeeze together). The oxygen we breathe is delivered to muscle cells by our blood. If the heart muscle stops receiving enough oxygen, the muscle will become damaged (a heart attack) and if the heart muscle stops receiving oxygen altogether, the heart will stop beating.

Reasons for the heart not receiving enough oxygen is commonly down to narrowing of the coronary arteries (the blood vessels that deliver blood to the heart) by fatty deposits. This is why we should have a balanced diet and watch our blood pressure, to keep our arteries in good shape and our hearts working.