Learning Objective

Describe the sequence linking a single action potential to skeletal muscle contraction and explain why electrical activity ends before force develops.

Mechanical Response to a Single Action Potential (High-Yield)

A single action potential in a skeletal muscle fiber triggers:

1. Membrane depolarization
2. Calcium (Ca²⁺) release from the sarcoplasmic reticulum
3. Cross-bridge formation
4. Muscle twitch (force generation)

Key concept:

1. The action potential is very short (~2 ms).
2. Force development is delayed because calcium must be released and bind to troponin before cross-bridge cycling begins.
3. The muscle membrane is fully repolarized before measurable tension develops.

This delay is called the latent period, and it represents excitation–contraction coupling.

Activity