The actin and myosin proteins are arranged very regularly in the cytoplasm of individual muscle cells referred to as fibers in both skeletal muscle and cardiac muscle, which creates a pattern, or stripes, called striations. The striations are visible with a light microscope under high magnification see Figure 7. Skeletal muscle fibers are multinucleated structures that compose the skeletal muscle.
Cardiac muscle, found within the heart, have fibers with one to two nuclei and are physically and electrically connected to each other so that the entire heart contracts as one unit.
Skeletal muscle is found attached to bones and exhibits voluntary control while cardiac muscle is involuntary. Because the actin and myosin are not arranged in such regular fashion in smooth muscle , the cytoplasm of a smooth muscle fiber which has only a single nucleus has a uniform, nonstriated appearance resulting in the name smooth muscle. However, the less organized appearance of smooth muscle should not be interpreted as less efficient.
Smooth muscle in the walls of arteries is a critical component that regulates blood pressure necessary to push blood through the circulatory system; and smooth muscle in the skin, visceral organs, and internal passageways is essential for moving all materials through the body.
Like cardiac muscle, smooth muscle is involuntarily controlled. Cardiac muscle tissue is only found in the heart. Highly coordinated contractions of cardiac muscle pump blood into the vessels of the circulatory system. Similar to skeletal muscle, cardiac muscle is striated and organized into sarcomeres, possessing the same banding organization as skeletal muscle Figure 7. However, cardiac muscle fibers are shorter than skeletal muscle fibers and usually contain only one nucleus, which is located in the central region of the cell.
Cardiac muscle fibers also possess many mitochondria and myoglobin, as ATP is produced primarily through aerobic metabolism. Cardiac muscle fibers cells also are extensively branched and are connected to one another at their ends by intercalated discs.
An intercalated disc allows the cardiac muscle cells to contract in a wave-like pattern so that the heart can work as a pump. Cardiac muscle is made from cells called cardiocytes. Like skeletal muscle cells cardiocytes have a striated appearance, but their overall structure is shorter and thicker. Cardiocytes are branched, allowing them to connect with several other cardiocytes, forming a network that facilitates coordinated contraction. See more from our free eBook library. Newark: University of Delaware, Biological Sciences.
How do muscles grow? Len Kravitz, Ph. Muscle Attachment and Actions. Muscular System Pathologies. When you select "Subscribe" you will start receiving our email newsletter. Use the links at the bottom of any email to manage the type of emails you receive or to unsubscribe. See our privacy policy for additional details. Learn Site. Artery walls include smooth muscle that relaxes and contracts to move blood through the body 3.
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