Which part of the living system did you change?
Labs / Biology
Sliding Filaments
Tap the muscle to fire a nerve signal — calcium floods in, uncovering the binding sites so myosin heads can grab the actin and ratchet it inward. Each stroke burns ATP and the whole sarcomere visibly shortens. Fire faster and the individual twitches fuse into a smooth, powerful tetanus.
Labs / Biology / Sliding Filaments
Sliding Filaments
Tap the muscle to fire a nerve signal — calcium floods in, uncovering the binding sites so myosin heads can grab the actin and ratchet it inward. Each stroke burns ATP and the whole sarcomere visibly shortens. Fire faster and the individual twitches fuse into a smooth, powerful tetanus.
Why it matters
Why explore this?
Living systems are connected and constantly changing. This model makes one biological process visible so you can test how its parts affect one another.
Explore
Try the model
length 2.20 µmtension 0%Ca²⁺ 0%ATP 0
Investigate
Questions to test
Predict first, try it in the model, then use what you observe to answer.
What to try
- Set “Twitch” and tap once. How long does the tension last after a single calcium pulse, and why does it fade?
- Slide the frequency up from 10 to 50 Hz. At what point do the separate twitches stop dipping back down and fuse into steady tetanus?
- Drag ATP toward 0 while stimulating hard. Why does the sarcomere stop sliding even though calcium is still high?
- Watch the ATP counter climb. Does holding a strong tetanus cost more fuel than the same muscle at rest?
- Compare the calcium trace with the tension trace. Which one rises first, and what does that lag tell you about how the signal becomes force?
Explain
Make sense of what happened
Explain the process as a chain: a change happens, the system responds, and that response affects what happens next. Use an observation from the model as evidence.
Check
Before you leave
How did the system respond?
How would you explain that response?
If you can answer all three using evidence from the model, you understand the main idea. If not, return to Explore and change one setting at a time.