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How Muscles Contract

by Greg Crowther


In its unabridged form, this song (originally written for Biology 241 at South Seattle College) gradually builds a model of excitation-contraction coupling, i.e., the process by which motor neurons stimulate muscles to contract. The model is built by first singing only verse 5; then singing verses 4 and 5; then singing verses 3, 4, and 5; then singing verses 2, 3, 4, and 5; and finally singing verses 1, 2, 3, 4, and 5. Impatient students and instructors can simply sing the five verses in order once.


(1) A motor neuron transmits ACh;
ACh opens sodium channels;

(2) Sodium causes depolarization;
Depolarization triggers the SR....

(3) And the SR releases calcium ions,
And the calcium ions bind to troponin,

(4) And troponin gives tropomyosin a tug,
And tropomyosin accommodates myosin,

(5) And myosin pulls on the actin, child --
The myosin pulls on the actin.

Other Files


sheet music (with melody play-back)

Lesson Plan

Songs like this one can be used during class meetings and/or in homework assignments. Either way, the song will be most impactful if students DO something with it, as opposed to just listening.

An initial, simple follow-up activity could be to answer the study questions below. A more extensive interaction with the song might entail (A) learning to sing it, using the audio file and/or sheet music as a guide, or (B) designing kinesthetic movements ("dance moves") to embody it. The latter activity should begin with students identifying the most important or most challenging content of the song, and deciding how to illustrate that particular content.

Study Questions

(1) What does it mean that "tropomyosin accommodates myosin"?

(2) What does SR stand for?

(3) To depolarize a muscle cell, does sodium move into the cell or out of it?

(4) What does ACh stand for?

(Answers may be found on the answers page.)