A muscle contracts when the thin filaments slide
over the thick filaments toward the center of each sarcomere.
During contraction, the (1) move closer
together and the (2) gets smaller.
At rest, (3) molecules surround the
thin filaments and prevent myosin crossbridges from
binding with actin. When (4) is released
from a (5) neuron and binds with (6)
on the motor endplate, the muscle cell begins to (7).
A primary event in the contraction of a muscle cell
is the release of (8) from the sarcoplasmic
reticulum. These ions moves by (9)
into the cell and bind with the troponin and tropomysosin
(the T and T system). The attachment of the Calcium
causes the T and T system to re-configure (move a bit)
and opens up myosin crossbridge binding sites. Crossbridges
form with the actin and undergoes a power stroke. Each
power stoke requires (10).