Figure 29-2 Schematic representation of the triad junction of skeletal muscle shows the junctional foot protein (ryanodine receptor [RyR1]) and its associated proteins. In skeletal muscle, the α_1S -subunit of the dihydropyridine receptor (DHPR) participates in excitation-contraction coupling. These physical links transmit essential signals across the narrow gap of the triadic junction that activate RyR1 and release Ca²⁺ from the sarcoplasmic reticulum. (Adapted from Pessah IN, Lynch C III, Gronert GA: Complex pharmacology of malignant hyperthermia. Anesthesiology 84:1275, 1996.)