Final answer:
Excitation-contraction coupling is the link between an action potential and muscle contraction. The T-tubules and sarcoplasmic reticulum help transmit the signal and store Ca2+ ions.
Step-by-step explanation:
Excitation-contraction coupling is the link (transduction) between the action potential generated in the sarcolemma and the start of a muscle contraction. The trigger for calcium release from the sarcoplasmic reticulum into the sarcoplasm is a neural signal.
The two membrane structures that help transmit this signal and also serve as storage sites for Ca2+ ions are the T-tubules and the sarcoplasmic reticulum.