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. Author manuscript; available in PMC: 2016 Dec 16.
Published in final edited form as: Cell Calcium. 2015 Jan 25;58(4):349–356. doi: 10.1016/j.ceca.2015.01.007

Figure 1. Junctional membrane complexes (JMCs) in striated muscles.

Figure 1

Two types of three-dimensional (3D) electron microscopy (EM) technologies (EM tomography and serial block-face scanning EM) are used to demonstrate JMC nano 3D architectures in tibia anterior muscle (A, B) and in ventricular muscle (C, D) obtained from adult mice. Triads consisting of the terminal cisternae of the SR and T-tubules are located at the junction of A-band and I-band in fast skeletal muscles (A). The triad structure is depicted as a 3D geometric model reconstructed in EM tomography in B. In contrast, cardiac dyads formed by T-tubules and SR, are located near Z-lines (C, EM tomography) [8] and are widely distributed in the cytoplasm, associating with the T-tubule network (D, serial block-face scanning EM) [24]. E schematically shows the structure of JMCs and distribution of Ca2+ channel molecules in JMCs in cardiac muscle. DHPR, dihydropyridine receptor; RyR, ryanodine receptor; JP2, junctophilin 2; ER/SR, endo/sarcoplasmic reticulum; jSR, junctional SR; PM, plasma membrane; Nuc, nucleus.