These are the practice questions that we have created for this chapter. The form will grade itself, and show you any mistakes. These are different practice questions than you see in SI Review and in class!

I had a lot of requests, so here's the slides we've been using in SI.

This animation is done by the makers of your textbook, and it shows the steps by which the muscle contracts.

We're kicking off our exploration of muscles with a look at the complex and important relationship between actin and myosin. Your smooth, cardiac, and skeletal muscles create movement by contracting and releasing in a process called the sliding filament model. Your skeletal muscles are constructed like a rope made of bundles of protein fibers, and that the smallest strands are your actin and myosin myofilaments. Its their use of calcium and ATP that causes the binding and unbinding that makes sarcomeres contract and relax.

Hank calls in a friend to do his push ups for him today to explain how skeletal muscles work together to create and reverse movements. Hank and Claire also demonstrate the role size plays in motor units, the three phase cycle of muscle twitches, and how the strength and frequency of an impulse affects the strength and duration of a contraction. This episode also explains twitch summation, tetanus, and isotonic vs. isometric movements.

This animation specifically breaks down the individual steps of the crossbridge cycle.

The top image shows the sarcomere when the muscle is relaxed.

The bottom image shows the sarcomere when the muscle is contracted.

The document has an image for each stage of the crossbridge cycle - the process that allows the muscle to actually contract.