Compare and contrast smooth and skeletal muscle

Muscle tissue, made of up highly specialized cells for contraction, is one of the four basic tissue types in multicellular organisms. There are three types of muscle tissue: skeletal, smooth and cardiac. However, this essay will concentrate on comparing skeletal and smooth muscle, firstly in the way they are structured and secondly in their function.

Skeletal muscle is found in vertebral organisms and attaches to bone via tendons. Smooth muscle is found in blood vessel walls and lining the walls of visceral organs. Each type of muscle is structured to best provide the body with the movements it needs internally and externally. Almost every essential function in the body, whether it is breathing, digesting, controlling blood pressure or simply walking requires muscle tissue.

Both skeletal and smooth muscle use actin and myosin to build their contractile elements, however their arrangement is different. In both muscle types there are two types of filaments: thick and thin. Within skeletal muscle, actin and myosin are arranged in myofibrils. Thin filaments in skeletal muscle are formed from filamentous actin, nebulin, tropomyosin and troponin. The length of thin filaments is defined by nebulin to form filaments of 1µm in length (Martini). Thick filaments are composed of “about 300 myosin molecules, each made up of a pair of myosin subunits twisted around one another”. Myosin molecules bind to one another via their long tail, leaving the head free to bind to the nearest thin filament. Thick filaments also have a specific length of 1.6µm and between 10 and 12 µm in diameter (Martini). The arrangement of these myofilaments in myofibrils and repeating sarcomeres, gives skeletal muscle its striated and regular appearance, as shown in f...

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... T and I to move back in front of the myosin binding site, which prevents further cross bridges from forming.

In smooth muscle the myosin light chain has to be dephosphorylated to deactivate the myosin. This is done by the enzyme myosin light chain phosphatase and disrupts the interaction between the myosin and actin causing relaxation. MLCP is activated by a decrease in sarcoplasmic Ca2+.

Although the two main proteins, actin and myosin, that make the contractile nature of muscles are the same, their arrangement coupled with other proteins subsequently causes the overall structure to differ in many respects. The main function is essentially the same in every muscle type, however as the structure varies the function and resulting contraction is different. the way they contraction occurs is different. This shows how structure is adapted to function and vice versa.