Biology 304

Muscle Lab Equipment Overview

1. The chart recorder is on the left. It is simply a box with a source of paper and a motor which moves the paper at a speed that you choose; the paper speed selector is magnified on the left, the power switch is below the red light. The muscle contractions are recorded on this paper, and just as importantly, your observations and procedures (stimulus strength, load, addition of drugs, etc) are recorded by directly writing on the paper.

2. The dissected muscle is hooked up to a transducer whose role is to convert the muscle’s movement to an electrical signal proportional to the amount of movement. The transducer is the lowest piece of equipment on the retort stand in the photo at the left. The upper piece is the femur clamp, the middle piece is the electrode.

3. The recorder module is similar to your stereo’s amplifier – both take an electrical signal, amplify it and provide an output. The recorder module takes the electrical signal from the transducer, amplifies it and sends that amplified signal to the pen which then moves proportional to the signal strength. As the paper from the chart recorder moves, the pen produces a drawing of the muscle contraction.

And if all goes well...you get a tracing produced!

Note that in this example, the students have written down the part of the experiment they are doing "after loading" and have labelled each part of the tracing with the mass tested (e.g. 15 g, 85 g); they have also x'd out mistakes...this way there is no confusion as to what is a muscle contraction and what is an "oops".

R.F. Lauff Department of Biology St. Francis Xavier University Antigonish, NS Canada B2G 2W5