The human muscular systems consists of more than 650 different muscles responsible of movement within the body however skeletal muscle, smooth muscle and cardiac muscle are the three basic classification of muscles. (Caroline and Mary)The three types of muscles have a different appearance under the microscope, different contract strengths and located in different locations in the human body but share the ability to contract. Smooth muscle also referred to as involuntary muscle is found in the walls of hollow organs throughout the human body and the involuntary movements of the smooth muscle is triggered by the impulses travelling through the autonomic nervous system to the muscle. (Caroline and Mary) The smooth muscle cell is small with one nucleus at the center and spindle shaped and their arrangement within the muscle tissue allow the contraction and relaxation with greater elasticity. The smooth muscle remain in contracted for a long period of time, do not easily tire but act slowly.
Cardiac muscle have a striated and branched appearance due presence of intercalated discs fusing neighboring fibers that control the heart and whose contractions is involuntary triggered by both the autonomic nervous system and pacemaker cells found in the heart. (Caroline and Mary)Skeletal muscles contraction is voluntary and nervous impulses send from the brain in response to a stimuli directly control the muscles. The skeletal muscles contain myofibrils that compose of actin and myosin bands which form the sarcomere thus giving the striated appearance.