Meeting Abstract

P3.77  Jan. 6   The Role of Body Size and Motor Neuron Size in the Control of Ballistic Tongue Muscle Movements WALTZ, Micah J.*; BLANCHARD, Jordan; ANDERSON, Curt W.; Idaho State University; BYU Idaho; Idaho State University waltmica@isu.edu

This research investigated relationships between motor neuron and body size. It is unknown whether motor neurons change during either ontogenetic or evolutionary increases in body size. If the motor neurons increase in size proportional to the increase in body size, larger neurons would theoretically reach threshold and generate an action potential more slowly than smaller neurons. This hypothetical paradox needs to be accounted for if the animal is to maintain equivalent speeds of muscle movement. Feeding behavior in Anurans was used as a model system to identify the physiological parameters involved in feeding. Four species were selected, three from the genus Bufo, and the leopard frog, Rana pipiens. High-speed videography analysis was used to calculate timing, velocity, and acceleration of tongue muscle groups across an order of magnitude of body size. These variables were then compared to body mass, tongue mass, as well as the area and aspect ratio of the motor neurons innervating the tongue. There was not a statistically significant difference in motor neuron size among the body sizes, however, there was a significant decrease in velocity of the tongue as the animals increase in size. Because neuron sizes do not show a trend of significant increase with increasing body mass, slower tongue speeds are likely the result of larger tongues and larger muscles being slower due to the physics of moving a larger mass.