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: 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. The SR functions to regulate intracellular levels of calcium. Two terminal cisternae (where enlarged SR connects to the T-tubule) and one T-tubule comprise a triad—a “threesome” of membranes, with those of SR on two sides and the T-tubule sandwiched between them. Excitation-contraction coupling
Although the term excitation-contraction coupling confuses or scares some students, it comes down to this: for a skeletal muscle fiber to contract, its membrane must first be “excited”—in other words, it must be stimulated to fire an action potential. The muscle fiber action potential, which sweeps along the sarcolemma as a wave, is “coupled” to the actual contraction through the release of calcium ions ( Ca + +) from the SR.