Biomechanics and Neural Control of Ballistic Tongue Projection

弹道舌投射的生物力学和神经控制

• 批准号: 0215438
• 负责人: Kiisa Nishikawa
• 金额: $ 11.67万
• 依托单位: Northern Arizona University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-01 至 2004-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0215438&HistoricalAwards=false
• 关键词: Biomechanics; Neural; Control; Ballistic; Tongue

New insights in biology have often come from studies of animals that exhibit some extreme of performance. In such animals, principles of function common to all animals are exaggerated, and are therefore observed and studied more readily. Ballistic tongue projection in toads represents one such extreme of performance. During ballistic tongue projection, toad tongues can be projected from the mouth at accelerations exceeding 2000 m/s2. Previous and ongoing research in our laboratories has focused on elucidating the mechanisms by which the mouth opening muscles of toads produce the power required for this extremely rapid movement.During ballistic tongue projection, the mouth opening muscles of toads are activated for about 200 ms prior to rapid mouth opening. Inspired by this pattern of activation, the investigators developed a novel technique to quantify the in vivo force-velocity behavior of this muscle. The technique is similar to the well known quick-release or load-clamp techniques. The insertion of a muscle is attached to a dual servo motor force-lever, preserving the in vivo origin and line of action of the muscle. A stimulator is programmed to preactivate the muscle tetanically for a given time against a load that prevents the muscle from shortening. The force-lever is then released instantaneously to some smaller load that is varied systematically. The smaller the load, the greater the velocity of shortening.Preactivated isotonic force-velocity and power curves were constructed using data collected from these experiments, an innovation of this laboratory. The investigators have demonstrated that 200 ms preactivation increases the shortening velocity, and therefore the power output, of the mouth opening muscles of toads by about twenty-fold. They further showed that 200 ms preactivation increased the power output of a frog hind limb muscle by the same factor. These results suggest that enhancement of muscle power by isometric preactivation is likely a fundamental, though previously unknown, property of skeletal muscle.Both jaw and hind limb muscles shorten rapidly when clamped to smaller loads after 200 ms preactivation, and reach final velocity in a very short period of time (3-8 ms), which increases with increasing load. At the instant of release when the muscle is shortening rapidly, the force of shortening (F) is equal to mv/t, where m = the mass of that part of the muscle that is shortening plus the external load, v = the observed shortening velocity, and t = the time required to reach the observed velocity. The shorter the time required to reach a given velocity, the greater the force at the time of release. The present results demonstrate that the force of shortening increases substantially when muscles are preactivated compared to standard isotonic tests. The proposed studies will permit validation of this new technique, and quantification of the effects of preactivation on the force-velocity behavior of other muscles. This novel method has the potential to significantly impact the field of muscle physiology, and to inform our basic understanding of the mechanism of contraction in striated muscle.

生物学的新见解通常来自对表现出极端性能的动物的研究。在这样的动物中，所有动物共有的功能原理被夸大了，因此更容易观察和研究。蟾蜍中的弹道舌头投影代表了表现的极端。在弹道舌头投影期间，蟾蜍的舌头可以以超过2000 m/s2的速度从口腔中投射出来。以前的和正在进行的实验室研究的重点是阐明蟾蜍开口肌肉产生这种非常快速运动所需的能力的机制。弹道舌的投影，to嘴的嘴巴张开蟾蜍在快速开口之前被激活约200毫秒。受这种激活模式的启发，研究人员开发了一种新型技术来量化该肌肉的体内力速度行为。该技术类似于众所周知的快速释放或负载钳技术。肌肉的插入连接到双伺服摩托力杆上，保留体内肌肉的起源和作用线。对刺激器进行编程，以在给定时间内将肌肉进行预反应，以防止肌肉缩短。然后将力杠杆立即释放到一些系统地变化的较小载荷中。载荷越小，缩短的速度越大。使用从这些实验中收集的数据（该实验室的创新）构建了证实的等值力 - 速度和功率曲线。研究人员表明，200毫秒的预催化会增加蟾蜍嘴开口肌肉的缩短速度，因此增加了蟾蜍的速度。他们进一步表明，200毫秒的预催化使青蛙后肢肌肉的功率输出增加了相同的因素。这些结果表明，通过等距预催化来增强肌肉能力可能是骨骼肌的基本属性，但骨骼肌的特性。当降低到200毫秒后的载荷后，下巴和后肢肌肉迅速缩短，并且在很短的时间内（3-8毫秒）增加了最终的速度，随着增加的载荷而增加。在释放瞬间肌肉迅速缩短时，缩短的力（F）等于MV/T，其中M =缩短肌肉的那部分肌肉的质量加上外部负载，V =观察到的缩短速度，T =达到观察到的速度所需的时间。达到给定速度所需的时间越短，释放时的力就越大。目前的结果表明，与标准的等渗测试相比，当肌肉被预选时，缩短力大大增加。拟议的研究将允许验证这项新技术，并量化预催化对其他肌肉力量行为的影响。这种新颖的方法有可能显着影响肌肉生理的领域，并为我们对横纹肌肉收缩机理的基本理解提供理解。