Put It All Together · Muscles
Decision, spark, calcium, ratchet, tendon, bone — every time you move.
You decide to move. A motor neuron fires, acetylcholine crosses the gap, calcium floods the fibre and uncovers the grip sites, billions of myosin arms haul on actin, sarcomeres shorten in series, the pull gathers into the tendon, and a bone swings around a joint. Roughly a fifth of a second, start to finish.
There's more: decision, spark, calcium, ratchet, tendon, bone — every time you move. The full explanation — and the interactive version you can tap and quiz yourself on — lives in the app.
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