During the stress, heart rate, respiration rate and temperature increase. The reason for that is the influence of sympathetic nervous system, which starts the “fight or flight” system. As a result of this adrenaline (epinephrine) is released from adrenal glands. Adrenaline circulates through the body and brings a lot of physiological changes. The heart beats faster than normal, pushing blood to the muscles, heart, and other vital organs and as a consequence, the person undergoing these changes also starts to breathe more rapidly to deliver more oxygen to organs. Meanwhile, adrenaline triggers the release of glucose and fats from energy storages. These molecules flood into the bloodstream, supplying energy to all parts of the body. The temperature is rising due to increased metabolism.