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.
Visceral muscle contracts slower than skeletal muscle, but the contraction can be sustained over a longer period of time. Organs of the cardiovascular system, respiratory system, digestive system, and reproductive system are lined with smooth muscle. This muscle can be described as rhythmic or tonic.