T Tubules (a term abbreviated from the their full name
Tubules) are tunnel-like extensions of sarcolemma that
pass through muscle fibers from one side to the other.
It is due to the side-to-side (across the muscle) orientation of these
structures that they are referred to as "transverse".
T tubules play an important role in the physiology of
- Muscle action potential (that is, movement
of electrical charge) travelling along T tubules trigger the release
of calcium(2+) ions from the sarcoplasmic
- This allows the calcium (2+) ions to flood into the sarcoplasm,
- which causes actions and movements of proteins (including actin, myosin,
troponin, and tropomyosin) within the myofibrils that
eventually muscle contraction.