Question

(a) What is meant by 'heart beat' ? What is the usual heart beat rate at rest ?
(b) What change occurs in heart beats if a person runs for a while Why ?

Answer 1

(a) Heart beat: One complete contraction and relaxation of the heart is called a heart beat. The usual heart beat rate at rest is 72 times /minute.
(b) The heart beats faster when a person runs for a while because running involves the rapid contraction and relaxation of muscles which requires lots of energy. Energy can only be created with accelerated rate of respiration which requires greater supply of oxygen. This can only be provided by oxygenated blood with incfreased circluation. It is because of this reason that the heart pumps faster.