So once acetylcholine is released into this synaptic cleft, these acetylcholines are shown by these black dots. They basically bind to the membrane proteins on our sarcolema and that will depolarize our sarcoma. Now, once the sarcolema depolarizes, that action potential that is created on the sarcolema will travel into the cell via these deep imaginations known as our T tubule. So what these tubules basically do is they allow the action potential to very quickly and evenly spread throughout the entire muscle cell. So once our action potential travels into the cell, it will basically cause the activation of these channels found on the membrane of the sarcoplasmic reticulum. So remember, the sarcoplasmic reticulum is basically the specialized type of endoplasmic reticulum found inside our muscle cell.