Sports science

1. Fig. 10-3.
Myofibrils are
surrounded by
calcium-
containing
sarcoplasmic
reticulum.

2. Fig. 10-7. Review of thin and
thick filament structure

3. Fig. 10-9. Overview of
the process

4. Fig. 10-9. Overview of
the process
The muscle fiber is
stimulated.

5. Fig. 10-9. Overview of
the process
The muscle fiber is
stimulated.
Ca2+ ions are released.

6. Fig. 10-11. “End-
on” view of thick
& thin filaments,
showing the
effect of calcium
ions after release
from the S.R.

7. Fig. 10-9. Overview of
the process
The muscle fiber is
stimulated.
Ca2+ ions are released.

8. Fig. 10-9. Overview of
the process
The muscle fiber is
stimulated.
Ca2+ ions are released.
Thin filaments move to
middle of sarcomere.

9. Fig. 10-12
Calcium attaches to
troponin/ tropomyosin; they
roll away, exposing the
active site on actin.

10. Fig. 10-12
Myosin cross-bridges
attach to active site on
actin.
After attachment, the
cross-bridges pivot,
pulling the thin
filaments.

11. Fig. 10-12
A fresh ATP replaces the
ADP+Pi, allowing myosin
and actin to detach.
Energy from the
splitting of the fresh
ATP allows
repositioning of the
myosin head.

12. Fig. 10-12
This leads back to Step
1, which continues the
cycle as long as
calcium ions are
attached to
troponin/tropomyosin.

13. Fig. 10-9. Overview of
the process
The muscle fiber is
stimulated.
Ca2+ ions are released.
Thin filaments move to
middle of sarcomere.

14. Fig. 10-9. Overview of
the process
The muscle fiber is
stimulated.
Ca2+ ions are released.
Thin filaments move to
middle of sarcomere.
Muscle fiber contracts.

15. Fig. 10-9. Overview of
the process
The muscle fiber is
stimulated.
Ca2+ ions are released.
Thin filaments move to
middle of sarcomere.
Muscle fiber contracts.
Muscle tension
increases.