Download Sliding Filament Theory

“The
Sliding Filament
Theory”
Shortening of
sarcomeres = muscle
shortening
1. Nervous system tells a muscle to contract by
releasing a chemical messenger acetylcholine (Ach)
into the synaptic cleft
2. This causes sodium ion channels to open
and sodium rushes into the muscle fiber and
excite the muscle producing muscle action
potential.
3. Increased sodium levels inside the muscle
fiber causes the Sarcoplasmic Reticulum
(SR) to release calcium into the sarcoplasm.
SR is a specialized organelle in muscle cells
used to store calcium.
4. The presence of calcium causes ATP to
interact with the actin and myosin filaments
by changing their shape.
5. Myosin heads make crossbridges to actin
filaments which pulls the sarcomeres
together, contracting the muscle.
6. When an enzyme removes the chemcial
messanger ACh from receptors on the
sarcolemma, ATP detaches myosin heads
and calcium is pumped back into the SR and
the muscle relaxes
What happens to our muscles when we die?
Ca+2 leaks out and muscle contract – no ATP
to release contraction = Rigor Mortis