Transverse ductular system

…For this reason, most of the Ca ²⁺ in muscle fibers at rest is taken up into the lumen of the sarcoplasmic reticulum, and the Ca ²⁺ concentration around the myofilaments is only ^10-7 mol or less. On the other hand, the cell membrane of muscle fibers has tubular depressions in the interior in many places, which are called the transverse system (T system). Since the transverse tubules are in close contact with the sarcoplasmic reticulum in many places, the effect of action potentials or depolarization occurring in the muscle fiber cell membrane is immediately transmitted to the sarcoplasmic reticulum, and as a result, the Ca ²⁺ in the lumen of the sarcoplasmic reticulum is released into the muscle cytoplasm. …

*Some of the terminology that refers to the "transverse ductular system" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…このため静止状態の筋繊維内のCa^2＋は大部分筋小胞体内腔にとり込まれており，筋フィラメント周囲のCa^2＋濃度は10^－7mol以下にすぎない。一方，筋繊維の細胞膜は多くの部位で管状に内部におちくぼみをつくっており，これを横行小管系(T系)transverse systemという。横行小管は筋小胞体と多くの部位で密接しているので，筋繊維細胞膜におこる活動電位あるいは脱分極の影響は筋小胞体にただちに伝えられ，その結果，筋小胞体内腔のCa^2＋が筋細胞質中に放出される。…

※「横行小管系」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報