Parts of Nervous System. Nervous System: Nervous system is the chief controlling and coordinating system of the body. It controls and regulates all activities of the body, whether voluntary or involuntary, and adjusts the individual (organism) to the given surroundings.
Compared to skeletal muscle, smooth-muscle cells are small. They are spindle-shaped, about 50 to 200 microns long and only 2 to 10 microns in diameter. They have no striations or sarcomeres. Instead, they have bundles of thin and thick filaments (as opposed to well-developed bands) that correspond to myofibrils.
Your body is composed of three types of muscle: skeletal muscle, smooth muscle, and cardiac muscle. Skeletal muscle makes up 40 percent of your total body weight, and smooth muscle and cardiac muscle each make up 5 percent of total body weight. Your muscles must contract in order to facilitate vital bodily functions.