Transverse Tubule Sarcoplasmic Reticulum System

Figure 7-5 shows myofibrils surrounded by the T tubule-sarcoplasmic reticulum system. The T tubules are very small and run transverse to the myofibrils. They begin at the cell membrane and penetrate all the way from one side of the muscle fiber to the opposite side. Not shown in the figure is the fact that these tubules branch among themselves so that they form entire planes of T tubules interlacing among all the separate myofibrils. Also, where the T tubules originate from the cell membrane, they are open to the exterior of the muscle fiber. Therefore, they communicate with the extracellular fluid surrounding the muscle fiber, and they themselves contain extracellular fluid in their lumens. In other words, the T tubules are actually internal extensions of the cell membrane. Therefore, when an action potential spreads over a muscle fiber

Myofibrils

Triad of the -reticulum

Myofibrils

Triad of the -reticulum

Sarcolemma

, Terminal cisternae

Transverse tubule

Mitochondrion

-Sarcoplasmic reticulum

Transverse tubule

Sarcotubules

Sarcolemma

, Terminal cisternae

Transverse tubule

Mitochondrion

-Sarcoplasmic reticulum

Transverse tubule

Sarcotubules membrane, a potential change also spreads along the T tubules to the deep interior of the muscle fiber. The electrical currents surrounding these T tubules then elicit the muscle contraction.

Figure 7-5 also shows a sarcoplasmic reticulum, in yellow. This is composed of two major parts: (1) large chambers called terminal cisternae that abut the T tubules, and (2) long longitudinal tubules that surround all surfaces of the actual contracting myofibrils.

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Responses

  • marion
    What is the Transverse Tubule–Sarcoplasmic Reticulum System?
    3 years ago

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