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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]
The insertion of the latissimus dorsi muscle is found along the floor of the bicipital groove. The teres major muscle inserts on the medial lip of the groove. [citation needed] It runs obliquely downward, and ends near the junction of the upper with the middle third of the bone. It is the lateral wall of the axilla. [2]
By the end of the 1940s Szent-Györgyi's team had postulated with evidence that contraction of actomyosin was equivalent to muscle contraction as a whole. [10] But the notion was generally opposed, even from the likes of Nobel laureates such as Otto Fritz Meyerhof and Archibald Hill , who adhered to the prevailing dogma that myosin was a ...
T-tubules (transverse tubules) are extensions of the cell membrane that penetrate into the center of skeletal and cardiac muscle cells.With membranes that contain large concentrations of ion channels, transporters, and pumps, T-tubules permit rapid transmission of the action potential into the cell, and also play an important role in regulating cellular calcium concentration.
A sarcomere is defined as the segment between two neighbouring Z-lines (or Z-discs). In electron micrographs of cross-striated muscle, the Z-line (from the German "zwischen" meaning between) appears in between the I-bands as a dark line that anchors the actin myofilaments. Surrounding the Z-line is the region of the I-band (for isotropic). I ...
An impulse from a nerve cell causes calcium release and brings about a single, short muscle contraction called a muscle twitch. If there is a problem at the neuromuscular junction, a very prolonged contraction may occur, such as the muscle contractions that result from tetanus. Also, a loss of function at the junction can produce paralysis. [5]
The line aw represents a muscle fiber of length m with its origin at w and insertion into an aponeurosis (TT') at a. The fiber shortens to length m' and moves its insertion the distance d to point b. Note that the shortening muscle fiber does not pull the aponeurosis along the line of action of the fiber but rather rotates around its origin.
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.