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How do skeletal muscles differ from smooth muscles and cardiac muscle?
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Physiology
Adenosine triphosphate (ATP) is the power source of many biochemical reactions. It is produced in the cell structures and system listed at the left to energize the important life processes listed on the right. An abbreviated chemical formula of the structure of ATP is also shown. The two high-energy P―O―P bonds are responsible for its power.
In vertebrate physiology, muscle tissue is categorized into three distinct types: skeletal, cardiac, and smooth muscle. These types differ primarily in their appearance, control mechanisms, and functional roles within the body.12
Key Differences
- Skeletal Muscle: These muscles are attached to the skeleton and are responsible for voluntary movements, such as walking and lifting. They appear striated (striped) under a microscope due to the orderly arrangement of sarcomeres, which contain actin and myosin filaments. Skeletal muscle fibers are long, multinucleated, and under the control of the somatic nervous system.132
- Cardiac Muscle: Found exclusively in the heart, this muscle is also striated and contains sarcomeres, similar to skeletal muscle. However, it differs significantly because it is under involuntary control and exhibits rhythmic contractions regulated by the heart's pacemaker, the sinoatrial node.432
- Smooth Muscle: This type lacks the striations of the other two, giving it a uniform appearance. It is found in the walls of hollow organs, such as the stomach, intestines, and blood vessels. Smooth muscle is under involuntary control via the autonomic nervous system and is specialized for slow, sustained contractions that require less chemical energy than striated muscle.521