Muscle contraction can be a challenging topic for anatomy and physiology students because so many events happen in a very specific sequence. Students must connect the nerve signal at the neuromuscular junction with calcium release and the interactions between actin and myosin. This Sliding Filament Model sequencing activity gives students a hands-on way to learn about the process.

Rather than simply memorizing a diagram, students work with a series of illustrated cards showing the major events involved in muscle contraction. The sequence begins when a motor neuron stimulates the muscle fiber and follows the signal as an action potential travels across the sarcolemma and into the T tubules. Students receive the handout, use scissors to cut each frame and organize them in the correct order.

Sliding Filament Mechanism:

• A motor neuron releases acetylcholine at the neuromuscular junction.
• An action potential travels along the sarcolemma and into the T tubules.
• The sarcoplasmic reticulum releases calcium ions.
• Calcium binds to troponin, causing tropomyosin to move.
• Myosin-binding sites on actin become exposed.
• Myosin heads form cross-bridges with actin.
• The power stroke pulls the thin filaments toward the center of the sarcomere.
• ATP allows the myosin heads to detach and reset.
• Repeated cross-bridge cycling causes the thin filaments to slide and the sarcomere to shorten.

Using the Activity in an Anatomy & Physiology Unit

I use this activity as part of a muscular system unit in Anatomy and Physiology. It works particularly well after students have already learned the basic anatomy of a muscle fiber, including the sarcolemma, T tubules, sarcoplasmic reticulum, myofibrils, sarcomeres, actin, and myosin.

The cards can be completed individually, but I prefer having students work in pairs or small groups. After groups finish their sequences, we review the order as a class and discuss what is happening at each stage.

For an additional challenge, students can arrange only the images first and explain each step verbally before receiving the description cards. You could also scramble the cards again at the end of the unit and use them as a quick review before a quiz or test. The download includes the correct sequence with the descriptions, so you have the answers ready and can display them on a smart board for students to check their work.

Related Resources

Anatomy and Physiology Muscle Unit – all of the resources I use with the muscle unit

Sliding Filament Model Coloring – color the image according to the directions to understand the steps of muscle contraction

Sarcomere Coloring – Focus on a muscle cell and individual filaments involved in muscle contraction

Giant Microbes Plush Muscle – giant microbes has an excellent assortment of plush body parts!