A colorful cartoon neuron sends an electrical signal into a muscle fiber's T-tubule, surrounded by the Sarcoplasmic Reticulum.

Scene: A cartoon neuron sending an electrical signal to a muscle cell. Caption: “An electrical signal travels down the T-tubule deep into the muscle fiber.” Visual cues: Show a “T-Tubule” labeled as a blue tube running into the muscle. The signal (like a lightning bolt ⚡) travels through it. Sarcoplasmic Reticulum (SR) shown surrounding the T-tubule. See more