What does it mean when the sacrolemma is depolarized?

Answer 1

Let's begin at the beginning.

What is depolarization?

There are opposing charges inside and outside the cell. The inside of a cell is negative. The outside is positive.

What is a sarcolemma?

Sarco: muscle

Lemma: covering/barrier

Thus, the muscle cell covering is depolarized.

This means an electrical signal is now traveling down the sarcolemma which will eventually hit the Triad and lead to a muscle contraction.

I hope this helps! :)