Im pretty sure there are a variety of organs/ muscles that help your body function so I’m going to name a few.
The heart, the lungs, the stomach, and the brain.
But out of all of these I think the heart is one of the main body functions because it pumps blood throughout your body keeping you alive in the process.
MPD also known as Multiple Personalities Disorder is a disorder where you have more than one personality. It causes forgetfulness and also can be cause by abuse or trauma.