![]() Their wings exhibit a proximal-to-distal temperature gradient during rest and activity. If high and constant body temperatures in endotherms enable the specialization of their biochemical processes to high temperatures, what happens at the periphery, where the temperature is not necessarily high nor constant? Does muscle contractile performance remain optimal at body temperature, or can this trait be optimized to cooler temperatures in muscles of endotherms which may operate at cooler temperatures during critical behaviours?īats are endotherms with remarkable appendicular anatomy that makes them ideally suited to address questions of muscle performance as it relates to operating temperature ( figure 1). For muscles in which temperatures are maintained at an endothermic core body temperature, one might expect that performance is specialized for operation at this temperature, declining at both cooler and warmer temperatures. In muscle, faster reaction kinetics at warmer temperatures results in faster force development, activation, relaxation and greater shortening velocity. Muscles are powered by a series of biochemical reactions that are under the kinetic constraints common to physiological systems: reaction rates are dependent on temperature. ![]() Some locomotor muscles are thus situated in parts of the body susceptible to temperature variation due to regional heterothermy, though this temperature variation is frequently overlooked when considering the effects of temperature on physiological function in endotherms. Limbs have high surface-area-to-volume ratios that make them vulnerable to excessive heat loss and useful for dumping heat, and their mechanical function is integral to locomotion. In this latter case, peripheral regions of the body are allowed to cool to insulate the core and to reduce metabolic energy expenditures directed towards heating. Variation in temperature among body regions, known as regional heterothermy, is both a consequence of the exchange of heat between a warm body and cooler environment and, in some cases, an adaptation to conserve energy. Body temperature is neither always high nor constant in endotherms, however. It has been proposed that this may enable the specialization of physiological processes to higher temperatures at which biochemical rates are faster. This study is the first to demonstrate differences in temperature sensitivity along the length of a single limb in an endotherm and suggests that temperature variation may be underappreciated as a determinant of locomotor performance in endotherms generally.Įndotherms, such as mammals and birds, maintain relatively high and constant body temperatures. ![]() This suggests that cooling of the distal wing muscles imposes a selective pressure on muscle contractile function which has led to shifts in temperature sensitivity. ![]() We found that the contractile properties of the pectoralis were significantly more temperature sensitive than those of the distal muscles. We measured contractile rates across temperatures in the proximal pectoralis muscle and an interosseous in the handwing of Carollia perspicillata, a small neotropical fruit bat, and compared their thermal dependence with that of a forearm muscle measured in a previous study. Because distal wing muscles are colder during flight than proximal muscles, we hypothesized that they would be less temperature sensitive to compensate for temperature effects, resulting in proximal–distal differences in temperature sensitivity that match differences in muscle operating temperature. Bats maintain high body temperatures during flight, but their wing muscles cool under typical environmental conditions. Flight is a demanding form of locomotion, requiring fast activation and relaxation in wing muscles to produce the necessary wingbeat frequencies. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |