Final answer:
The T tubules communicate with the sarcoplasmic reticulum to release Ca++ at the Junctional triad. The junctional triad is where the T-tubule, which carries the action potential into the cell, is sandwiched between the membranes of the sarcoplasmic reticulum on either side. When the action potential reaches the membrane of the sarcoplasmic reticulum, calcium channels open and calcium diffuses out into the sarcoplasm, initiating muscle contraction.
Step-by-step explanation:
The T tubules communicate with the sarcoplasmic reticulum to release Ca++ at the Junctional triad. The junctional triad is where the T-tubule, which carries the action potential into the cell, is sandwiched between the membranes of the sarcoplasmic reticulum on either side. When the action potential reaches the membrane of the sarcoplasmic reticulum, calcium channels open and calcium diffuses out into the sarcoplasm, initiating muscle contraction.