ABSTRACT
Insect flight muscles are particularly interesting in that they usually have to act continuously, sometimes for long periods, at relatively high rates of power output. The myofibrils of most skeletal muscles are surrounded by a network of vesicular elements called the sarcoplasmic reticulum. At regular intervals there are structures known as “diads” or “triads”, in which a tubular element is situated next to one or two vesicular elements. In addition there are in some muscles neuromodulator axons whose action is to produce rather subtle effects on the functioning of the muscle system. Flight muscles commonly consist of a small number of separate motor units each innervated by a “fast”-type motor axon. The functional roles of inhibition and of neuromodulation in flight muscles have yet to be determined. Vesicles formed from membrane-bound sacs have been isolated from homogenized muscles, including locust flight muscles, by differential centrifugation.
