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Depiction of smooth muscle contraction. Muscle contraction is the activation of tension -generating sites within muscle cells. [ 1][ 2] In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as when holding something heavy in the same position. [ 1]
Skeletal muscle. Skeletal muscle (commonly referred to as muscle) is one of the three types of vertebrate muscle tissue, the other being cardiac muscle and smooth muscle. They are part of the voluntary muscular system [ 1] and typically are attached by tendons to bones of a skeleton. [ 2][ 3] The skeletal muscle cells are much longer than in ...
A muscle cell, also known as a myocyte, is a mature contractile cell in the muscle of an animal. [ 1] In humans and other vertebrates there are three types: skeletal, smooth, and cardiac (cardiomyocytes). [ 2] A skeletal muscle cell is long and threadlike with many nuclei and is called a muscle fiber. [ 3]
A sarcomere (Greek σάρξ sarx "flesh", μέρος meros "part") is the smallest functional unit of striated muscle tissue. [ 1] It is the repeating unit between two Z-lines. Skeletal muscles are composed of tubular muscle cells (called muscle fibers or myofibers) which are formed during embryonic myogenesis. Muscle fibers contain numerous ...
Sliding filament theory: A sarcomere in relaxed (above) and contracted (below) positions. The sliding filament theory explains the mechanism of muscle contraction based on muscle proteins that slide past each other to generate movement. [ 1] According to the sliding filament theory, the myosin ( thick filaments) of muscle fibers slide past the ...
Sarcoplasm. Sarcoplasm is the cytoplasm of a muscle cell. It is comparable to the cytoplasm of other cells, but it contains unusually large amounts of glycogen (a polymer of glucose), myoglobin, a red-colored protein necessary for binding oxygen molecules that diffuse into muscle fibers, and mitochondria. [ 1][ 2][ 3] The calcium ion ...
A tetanic contraction (also called tetanized state, tetanus, or physiologic tetanus, the latter to differentiate from the disease called tetanus) is a sustained muscle contraction [2] evoked when the motor nerve that innervates a skeletal muscle emits action potentials at a very high rate. [3] [4] During this state, a motor unit has been ...
Sarcolemma. Skeletal muscle fibre, with sarcolemma labeled at upper left. The sarcolemma ( sarco (from sarx) from Greek; flesh, and lemma from Greek; sheath), also called the myolemma, is the cell membrane surrounding a skeletal muscle fibre or a cardiomyocyte. [ 1][ 2] It consists of a lipid bilayer and a thin outer coat of polysaccharide ...