Some people may void their bowels or bladder. This was useful during caveman times to avoid rupture of the bowels or bladder, but it is problem now that we wear clothes.
The pituitary gland unleashes a hormone into the bloodstream that prompts the release of the stress hormone cortisol from the adrenal cortex. Glucose is produced and released, making more of it available to the muscles, thus giving the body more energy.
The blood that is drained from these areas of the body is pumped into the muscles and other vital organs, preparing them for quick and powerful action. All the senses become sharper, so you are more aware of your surroundings and more information is being sent to the brain for processing. The muscles heat up and swell, giving the illusion of larger size. As the muscles receive this oxygenated blood, they quiver with energy, so you began to tremble and you legs shake. Explosive power is on tap and ready for tremendous exertion of energy. The body is ready to take flight or to fight.