Meeting Abstract
Some striated muscles are multi-functional; i.e., they are able to serve several different roles during locomotion and movement, including acting as motors, brakes, struts, or springs. We discovered a multi-function muscle, the nuchal retractor, in the comparatively simple muscular system of a cephalopod mollusc. Synchronized measurements of head movement and muscle activation revealed that while the mitochondria-poor nuchal retractor muscle fibers were activated only for head retractions that occurred during escape jet locomotion, the mitochondria-rich muscle fibers served three roles during escape jets: as motors to assist in head retraction, as struts to stabilize head position briefly during changes in swimming direction, and as brakes to control the head extensions that followed an escape jet. The nuchal retractor demonstrates that multi-functionality is not restricted to the muscles of animals with jointed skeletal support systems, and also provides a relatively simple model in which to investigate the physiology of multi-function muscles.
