Title: 15.4: Muscle Contraction - Biology LibreTexts
Headings: 15.4: Muscle Contraction
15.4: Muscle Contraction
Arm Wrestling
Muscle Contraction
How a Skeletal Muscle Contraction Begins
Excitation-contraction coupling
Sliding Filament Theory of Muscle Contraction
Crossbridge Cycling
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Content: Propagation of an action potential along the sarcolemma enters the T-tubules. For the action potential to reach the membrane of the SR, there are periodic invaginations in the sarcolemma, called T-tubules (“T” stands for “transverse”). The arrangement of a T-tubule with the membranes of SR on either side is called a triad (Figure 15.4. 3 ). The triad surrounds the cylindrical structure called a myofibril, which contains actin and myosin. The T-tubules carry the action potential into the interior of the cell, which triggers the opening of calcium channels in the membrane of the adjacent SR, causing Ca + + to diffuse out of the SR and into the sarcoplasm. It is the arrival of Ca + + in the sarcoplasm that initiates contraction of the muscle fiber by its contractile units, or sarcomeres. Figure 15.4. 3: Narrow T-tubules permit the conduction of electrical impulses.