Answer:
The correct answer will be- Transverse tubules
Step-by-step explanation:
Transverse tubules are the tubular structure formed by the extension of the plasma membrane which innervates the cardiac and skeletal muscle cells. The T-tubules structure is structured between 20-40 nm and located at the junction of the I and A band.
The signals from the motor neurons once raches the motor endplate in muscles are carried into the muscles by these T-tubules which transmits the signals to muscle cells at very high speed. The T-tubules cause the release of the Calcium ions from the sarcoplasmic reticulum that cause contraction of the skeletal muscle.
Thus, Transverse tubules are the correct answer.