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( Skeletal muscle)
Skeletal muscle is a type of striated muscle, which usually attaches to tendons. Skeletal muscles are used to create movement, by applying force to bones and joints; via contraction. They generally contract voluntarily (via somatic nerve stimulation), although they can contract involuntarily through reflexes. The whole muscle is wrapped in a special type of connective tissue, epimysium. Skeletal muscles have one end (the "origin") attached to a bone closer to the centre of the body's axis and this is often but not always a relatively stationary bone (such as the scapula) and the other end (the "insertion") is attached across a joint to another bone further from the body's axis (such as the humerus). Contraction of the muscle causes the bones to rotate about the joint and the bones to move relative to one another (such as lifting of the upper arm in the case of the origin and insertion described here). There are several different ways to categorize the type of skeletal muscle fibers (see below). One method uses the type of protein contained in myosin (one of the important proteins that is responsible for the ability of muscle to contract). Using this classification scheme, there are two major types of fibers for skeletal muscles Type I and Type II. Type I fibers appear reddish. They are good for endurance and are slow to tire because they use oxidative metabolism. Type II fibers are whitish; they are used for short bursts of speed and power, and use both oxidative metabolism and anaerobic metabolism depending on the particular sub-type, and are therefore quicker to fatigue. The strength of skeletal muscle is directly proportional to its length and cross-sectional area. The strength of a joint, however, is determined by a number of biomechanical principles, including the distance between muscle insertions and pivot points and muscle size. Muscles are normally arranged in opposition so that as one group of muscles contract, another group 'relaxes' (in fact simply stretched) or lengthens. Antagonism in the transmission of nerve impulses (epsp and ipsp lateral balance) to the muscles means that it is impossible to stimulate the contraction of two antagonistic muscles at any one time. During ballistic motions such as throwing, the antagonist muscles act to 'brake' the agonist muscles throughout the contraction, particularly at the end of the motion. In the example of throwing, the chest and front of the shoulder (anterior Deltoid) contract to pull the arm forward, while the muscles in the back and rear of the shoulder (posterior Deltoid) also contract and undergo eccentric contraction to slow the motion down to avoid injury. Part of the training process is learning to relax the antagonist muscles to increase the force input of the chest and anterior shoulder.
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Skeletal muscle Subcategories
Skeletal muscle Articles
Time course of muscle soreness following different types of exercise
Time course of muscle soreness following different types of exercise
Andrew J Vickers
Integrative Medicine Service, Biostatistics Service, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, 10021, USA
B...
Hedgehog can drive terminal differentiation of amniote slow skeletal muscle
Hedgehog can drive terminal differentiation of amniote slow skeletal muscle
Xiaopeng Li* 1 , Christopher S Blagden* 1, 2 , Heidi Bildsoe* 1 , Marie Ange Bonnin
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