Compare and Contrast Cardiac and Skeletal Muscle. Discuss How Their Differences Enable Them to Carry Out Their Function More Effectively.

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Compare and contrast Cardiac and Skeletal Muscle. Discuss how their differences enable them to carry out their function more effectively. Skeletal, cardiac and smooth muscle account for nearly half of our body weight, their roles essential for normal bodily function. Skeletal muscles; attached to the skeleton via tendons; maintain body posture, are voluntary controlled and have antagonistic arrangement for muscular contractions. They tend to enlarge following vigorous exercise, a phenomenon called muscular hypertrophy and are located around the body. Conversely, cardiac muscle is confined only to the heart, its main role being to distribute blood. Its myogenic nature means contractions are under involuntary control and cause prevention from fatigue. The natural beating rhythm is adjusted via sympathetic and parasympathetic neurons of the CNS to suit physiological conditions. The function of these muscles is closely related to their structure and any differences in structure allow these two types of muscle to be identified. Cardiac and skeletal muscle is excitable tissue where stimulation of a single muscle fibre leads to excitation of a whole cell. They undergo contractions in response to an action potential, either resulting in pumping blood into pulmonary and systemic circulation or the movement of limbs. The contractile unit in both tissues is the same, the differences lie in the arrangement of these units and associate structures. The contractile unit consists of myofibrils which encompass repeating units of sarcomeres running end to end giving a striated appearance to the muscle. Each sarcomere is characterized by two z-lines, one M-line, an A-band and an H-zone. Actin and myosin are the principle proteins in the contractile machinery with myosin dominating the A-band. The latter refracts plane polarized light (anisotropy) giving a dark appearance to

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