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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 T-tubule surrounded by two terminal cisternae is called a triad. The terminal cisternae, along with the transverse tubules, are the mechanisms of transduction from a nervous impulse to an actual muscle contraction .
Within the t-tubules, distinct ion channels and cellular proteins are present within the t- tubule bilayer that allow movement of calcium influx from the extracellular space into the myocyte to initiate depolarization and contraction. Once traveling through the t- tubules, the calcium arrives at the sarcoplasmic reticulum.
In the histology of skeletal muscle, a triad is the structure formed by a T tubule with a sarcoplasmic reticulum (SR) known as the terminal cisterna on either side. [1] Each skeletal muscle fiber has many thousands of triads, visible in muscle fibers that have been sectioned longitudinally. (This property holds because T tubules run ...
T tubule: transverse intracellular tubules invaginating from the cell membrane and surrounding the myofibrils of the T system of skeletal and cardiac muscle, serving as a pathway for the spread of electrical excitation within a muscle cell; Trachea: tubules forming the respiratory system of most insects and many arachnids
This network is composed of groupings of two dilated end-sacs called terminal cisternae, and a single T-tubule (transverse tubule), which bores through the cell and emerge on the other side; together these three components form the triads that exist within the network of the sarcoplasmic reticulum, in which each T-tubule has two terminal ...
The sarcoplasmic reticulum is a network of the tubules that extend throughout muscle cells, wrapping around (but not in direct contact with) the myofibrils (contractile units of the cell). Cardiac and skeletal muscle cells contain structures called transverse tubules (T-tubules) , which are extensions of the cell membrane that travel into the ...
In skeletal muscle, there is a very high concentration of L-type calcium channels, situated in the T-tubules. Muscle depolarization results in large gating currents, but anomalously low calcium flux, which is now explained by the very slow activation of the ionic currents.