Reaction which is caused due to sadness, emotional disorder, distress,etc. is called Stress reaction.It is also caused due to sudden shocks and mental disorder. Due to sadness a change occurs in the sensible nervous system. Due to this sudden nervous disorder, our heart starts beating faster with our tear glands opening up as we are going to cry. For this reason we do not have any sensation for hunger or almost go numb and we recover after a few days when the shock leaves.