There are two kinds of trembling of the body, and two kinds of standing of the hair on end. Such phenomena occur either in great spiritual ecstasy or out of great fear under material conditions. There is no fear in transcendental realization.
Spiritual feelings of happiness and intense ecstasies have no mundane comparison. Therefore it is very difficult to give expression to such feelings. We can just have a glimpse of such ecstasy in the words of Sri Narada Muni. Each and every part of the body or senses have their particular part of function. After seeing the Lord, all the senses became fully awakened to render service unto the Lord because in the liberated state of the senses from mundane contingency, they are fully efficient in serving the Lord.
Compiled from Srila Prabhupada's Teachings