Hand-held model of a sarcomere to illustrate the sliding filament mechanism in muscle contraction.

From our teaching of the contractile unit of the striated muscle, we have found limitations in using textbook illustrations of sarcomere structure and its related dynamic molecular physiological details. A hand-held model of a striated muscle sarcomere made from common items has thus been made by us to enhance students' understanding of the sliding filament mechanism as well as their appreciation of the spatial arrangements of the thick and thin filaments. The model proves to be quite efficacious in dispelling some alternative conceptions held by students exposed previously only to two-dimensional textbook illustrations and computer graphic displays. More importantly, after being taught by this hand-held device, electronmicrographic features of the A and I bands, H zone, and Z disk can be easily correlated by the students to the positions of the thick and thin elements relatively sliding past one another. The transverse expansion of the sarcomere and the constancy of its volume upon contraction are also demonstrable by the model.