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Skeletal Muscle Striated, multinucleated, have sarcomeres, T-Tubules, Inward Na current for depolarization, bell curve for AP, AP opens voltage gated Ca channels in SR, Basis for contraction is when Ca binds to troponin, not a functional syncytium, contraction is not dependent on extracellular Ca. Cardiac Muscle Striated, one nucleus per cell, connected by gap junction, have sarcomeres, T-Tubules, Depolarization starts on inward Ca for SA node and inward Na for cardiac, Bell for SA Node and Plateau AP for cardiac, longest duration for AP, AP opens slow voltage-gated Ca channels, Ca channels are open during plateau, Ca released from SR, Basis for contraction is Ca troponin binding, Functional Syncytium, partially dependent on extracellular Ca, Contraction is not dependent on stimulation by motor neurons! Smooth Muscle no striations, very small, narrow and short, one nucleus, connected by gap junctions, no sarcomeres, T-Tubules not present, inward Na for depolarization, AP opens Ca channels in cell membrane, inward Ca current, Basis for contraction is Ca Calmodulin Binding and Myosin light chain kinase activation [Ca binds to Calmodulin, MLCK activated, myosin is phosphorylated], Functional Syncytium, Contraction is dependent on extracellular Ca