If you're seeing this message, it means we're having trouble loading external resources for Khan Academy.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Muscles

4 videos
Without muscles, we wouldn't be able to do much of anything. This tutorial begins to explore what muscle cells are and how they contract in order to move our bodies (or do things like breath and pump blood).

Myosin and actin

VIDEO 9:38 minutes
How myosin and actin interact to produce mechanical force.

Tropomyosin and troponin and their role in regulating muscle contraction

VIDEO 9:22 minutes
Tropomyosin and troponin and their role in regulating muscle contraction. How calcium ion concentration dictates whether a muscle is contracting or not.

Role of the sarcoplasmic reticulum in muscle cells

VIDEO 14:42 minutes
The role of the sarcoplasmic reticulum in controlling calcium ion concentrations within the muscle cell.

Anatomy of a skeletal muscle fiber

VIDEO 16:32 minutes
Understanding the structure of a muscle fiber