Skeletal Muscle vs Cardiac Muscle
All the animals are encompassed by muscles, which act as an indicator for the anatomy of the body. Muscle is a contractile tissue, which is derived from the mesoderm layer of embryonic germ cells. Mainly muscle is composed of muscle cells. Muscles are classified into skeletal muscle, cardiac muscle, and smooth muscle. Their function produce force causing motion; i.e. they can cause movement of internal organs or locomotion of the organism itself.
According to the functions the muscles are classified as voluntary and involuntary muscles. Skeletal muscle is the voluntary muscle in which contraction occurs with conscious thought; but cardiac and smooth muscles are involuntary in which contraction occurs without conscious thought.
Based on its structure skeletal muscle is called striated muscle. Its function is controlled by somatic nervous system. Most of the muscles are attached to the bones by tendons, which are bundles of collagen fibers.
Mainly, skeletal muscle is composed of muscle cells or myocytes; sometimes collectively called as muscle fibers. These are formed from the fusion of developmental cells known as myoblast into long, cylindrical, multinucleated cells. Muscle fibers are composed of myofibrils such as actin (thin filament) and myosin proteins (thick filament). Under the microscope view, these two filaments appear in skeletal muscle with distinctive banding patterns. In addition to these two, muscle fibers contain troponin and tropomyosin, which are essential for muscle contraction. Actin and myosin are arranged in a repeating unit called as sarcomere. It is the basic functional unit of muscle fiber and responsible for the striated appearance. Interaction of actin and myosin is responsible for the muscle contraction.
Skeletal muscle is categorized into two types; type one fiber appears red due to the presence of oxygen binding protein known as myoglobin while the other fiber is white due to the absence of myoglobin.
Depending on their twitch capabilities skeletal muscle fibers are classified into fast twitch fiber and slow twitch fiber. Skeletal muscle cells are excitable and are subjected to depolarization by the neurotransmitter acetylcholine.
Cardiac muscle is specifically found in the myocardium of the heart, and it is a striated and involuntary muscle. Cardiac muscle is composed of cardiac muscle cells, which are called cardiomyocytes, which have one, two, or rarely three or four nuclei. Cardiac muscle cells, like all tissues in the body, depend on ample blood supply not only to deliver oxygen and nutrients but also to remove the waste products. Due to the coordinated contraction of heart muscle cells, the blood is propelled from the artia and ventricles to the blood vessels of the circulatory system. These actions make up the systole of the heart.
Cardiac muscle has a large number of mitochondria, which helps the continuous aerobic respiration, numerous myoglobins, and good blood supply.
Cardiac muscle also exhibits cross striations by alternating thick and thin filaments. Under the electron microscope view, actin filaments appear thin band while the myosin filament appears thick and darker. Cardiac muscle cells are mostly branched. T-tubules in the cardiac muscle are larger, broader and run along the Z-Discs. Intercalated discs are connecting cardiac myocytes to an electrochemical syncytium and are responsible for force transmissions during muscle contraction. Diaids are formed between the T-tubules .T tubules play an important role in excitation-contraction-coupling (ECG).
What is the difference between Skeletal Muscle and Cardiac Muscle?
• Skeletal muscles are found in almost all part of the animal body while the cardiac muscles are found only in the myocardium of the heart.
• Skeletal muscle cell is linear and longitudinal while the cardiac muscle cell is branched.
• When compared to skeletal muscle, T-tubules in the cardiac muscle are larger, broader, and run along the Z-Discs.
• Compared to skeletal muscle T-tubules are fewer in cardiac muscle.
• Cardiac muscle forms diads instead of the traids, which is formed between the T-tubules and sarcoplasmic reticulum in skeletal muscle.
• Skeletal muscle is a voluntary muscle while the cardiac muscle is involuntary.
• Cardiac muscle requires extracellular calcium ions for the contraction but not need for skeletal muscle contraction.
• Cardiac muscle consists of intercalated discs, but skeletal muscle cells don’t have that.