This occurs in striated muscle (skeletal and cardiac) after specific binding sites on the actin have been exposed in response to the interaction between calcium ions (Ca ++ ) and proteins (troponin and tropomyosin)… Muscle is one of the four primary tissue types of the body, and the body contains three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle ( Figure 10.2 ).

Ca ++ also is required for the contraction of smooth muscle, although its role is different: here Ca ++ activates enzymes, which in turn activate myosin heads. While the nervous system can influence the excitability of cardiac and smooth muscle to some degree, skeletal muscle completely depends on signaling from the nervous system to work properly.

cardiac muscle — striated muscle found in the heart; joined to one another at intercalated discs and under the regulation of pacemaker cells, which contract as one unit to pump blood through the…. skeletal muscle — striated, multinucleated muscle that requires signaling from the nervous system to trigger contraction; most skeletal muscles are referred to as voluntary muscles that move bones…. smooth muscle — nonstriated, mononucleated muscle in the skin that is associated with hair follicles; assists in moving materials in the walls of internal organs, blood vessels, and internal…. Ca ++ — removed and the actin-binding sites are re-shielded.

Be able to describe the different types of muscle; explain contractibility and extensibility; describe the layers of connective tissues packaging skeletal muscle.