Why does pulse rate change with different situations?

Answer 1

Pulse changes depending on hormones and the signals from the autonomic nervous system. The hormones and signals are used to increase heart rate when oxygen demand is higher, such as when one is under a fight-or-flight response, or if one is exercising heavily. When someone tries to relax, opposite signals slow the heart rate to give it a rest, since the body no longer needs as much oxygen.