PHSI 208 Lecture Notes - Lecture 18: Endoplasmic Reticulum, T-Tubule, Sarcolemma
Document Summary
Ap propagate form the sarcolemma to the interior of muscle fibers along the transverse tubule network. Sarcolemma penetrates into the muscle fibre in the form of t-tubules and wrap around each myofibril in specific regions. Specialized ca2+ storage organelles known as sarcoplasmic reticulum are strategically organized w/ the t-tubules. The ultimate intracellular signal that triggers contraction in all muscle types is a rise in intracellular calcium [ca2+]i (for all types of muscle) Ca2+ can enter the sarcoplasm from the extracellular space via voltage-gated ca2+ channels or can be released into the sarcoplasm form the intracellular ca2+ storage reservoir of the sarcoplasmic reticulum. It can also be a combination of both (e. g. skeletal muscle) The process by which electrical excitation of the surface membrane triggers an increase of [ca2+]i in muscle is known as excitation-contraction coupling. Action potentials propagate from the sarcolemma to the interior of muscle fibers along the transverse tubule network.
