The skeletal muscle action potential | MDS entrance preaparations

The skeletal muscle action potential-
A. Is not essential for contraction to occur
B. Has a prolonged plateau phase
C. Spreads inward to all parts of the muscle via the t-tubule system
D. Begins with an inward movement of K+ ions

Ans. (C)

•          The skeletal muscle fibre is so large that action potential spreading along its surface membrane cause almost no current flow deep within the fibre.

•          Current penetration deeply into the muscle fibre to the vicinity of separate myofibrils is achieved by transmission of Action Potentials along 'Transverse tubules' (T tubules) that penetrate all the way through the muscle fibre.

•          The T tubule action potentials cause release of calcium ions inside the muscle fibres, which then cause contraction. This entire process is called 'Excitation-Contraction' coupling.