Neuromuscular control of prey capture in frogs

SUMMARY The mammalian tongue is believed to fall into a class of organs known as muscular hydrostats, organs for which muscle contraction both generates and provides the skeletal support for motion. We propose that the myoarchitecture of the tongue, consisting of intricate arrays of muscular fibers, forms the structural basis for hydrostatic deformation. Owing to the fact that maximal diffusion of the ubiquitous water molecule occurs orthogonal to the short axis of most fiber-type cells, diffusion-weighted magnetic resonance imaging (MRI)measurements can be used to derive information regarding 3-D fiber orientation in situ. Image data obtained in this manner suggest that the tongue consists of a complex juxtaposition of muscle fibers oriented in orthogonal arrays, which provide the basis for multidirectional contraction and isovolemic deformation. From a mechanical perspective, the lingual tissue may be considered as set of continuous coupled units of compression and expansion from which 3-D strain maps may be derived. Such functional data demonstrate that during physiological movements, such as protrusion, bending and swallowing, hydrostatic deformation occurs via synergistic contractions of orthogonally aligned intrinsic and extrinsic fibers. Lingual deformation can thus be represented in terms of models demonstrating that synergistic contraction of fibers at orthogonal or near-orthogonal directions to each other is a necessary condition for volume-conserving deformation. Evidence is provided in support of the supposition that hydrostatic deformation is based on the contraction of orthogonally aligned intramural fibers functioning as a mechanical continuum.

Section: Hydrostatic Model Of Lingual Deformationmentioning

confidence: 99%

Section: Lingual Myoarchitecture and Hydrostatic Deformationmentioning

confidence: 99%

Anatomical basis of lingual hydrostatic deformation

Gilbert

Napadow

Gaige

et al. 2007

“…Recent comparative studies have shown that, among anurans, toads (genus Bufo) appear to be particularly adapted for ballistic tongue projection (Nishikawa, 1999;Nishikawa, 2000). Forward-dynamic biomechanical models have shown that the paired depressor mandibulae muscles produce >90% of the force needed for ballistic tongue projection in anurans (Mallett et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

Storage and recovery of elastic potential energy powers ballistic prey capture in toads

Lappin

Monroy

Pilarski

et al. 2006

Self Cite

102

115

SUMMARY Ballistic tongue projection in toads is a remarkably fast and powerful movement. The goals of this study were to: (1) quantify in vivo power output and activity of the depressor mandibulae muscles that are responsible for ballistic mouth opening, which powers tongue projection; (2) quantify the elastic properties of the depressor mandibulae muscles and their series connective tissues using in situ muscle stimulation and force-lever studies; and (3) develop and test an elastic recoil model, based on the observed elastic properties of the depressor mandibulae muscles and series connective tissues, that accounts for displacement, velocity, acceleration and power output during ballistic mouth opening in toads. The results demonstrate that the depressor mandibulae muscles of toads are active for up to 250 ms prior to mouth opening. During this time, strains of up to 21.4% muscle resting length (ML) develop in the muscles and series connective tissues. At maximum isometric force, series connective tissues develop strains up to 14% ML, and the muscle itself develops strains up to 17.5%ML. When the mouth opens rapidly, the peak instantaneous power output of the depressor mandibulae muscles and series connective tissues can reach 9600 W kg–1. The results suggest that: (1) elastic recoil of muscle itself can contribute significantly to the power of ballistic movements; (2) strain in series elastic elements of the depressor mandibulae muscle is too large to be borne entirely by the cross bridges and the actin–myosin filament lattice; and (3) central nervous control of ballistic tongue projection in toads likely requires the specification of relatively few parameters.

“…As muscles provide the necessary force, elastic potential energy is stored in elastic elements while a catch of some sort (e.g. a latch or antagonistic muscle activity) prevents the movement until a later time (Gronenberg, 1996;Nishikawa, 1999;Burrows, 2003;Wilson et al, 2003;Patek et al, 2007). In human walking, such function allows higher ankle power output than what muscle fibers could produce (for power output of muscle fibers of the ankle extensors, see Appendix 1).…”

mentioning

confidence: 99%

Impulsive ankle push-off powers leg swing in human walking

Lipfert¹,

Günther

Renjewski

et al. 2013

Rapid unloading and a peak in power output of the ankle joint have been widely observed during push-off in human walking. Modelbased studies hypothesize that this push-off causes redirection of the body center of mass just before touch-down of the leading leg. Other research suggests that work done by the ankle extensors provides kinetic energy for the initiation of swing. Also, muscle work is suggested to power a catapult-like action in late stance of human walking. However, there is a lack of knowledge about the biomechanical process leading to this widely observed high power output of the ankle extensors. In our study, we use kinematic and dynamic data of human walking collected at speeds between 0.5 and 2.5 m s −1 for a comprehensive analysis of push-off mechanics. We identify two distinct phases, which divide the push-off: first, starting with positive ankle power output, an alleviation phase, where the trailing leg is alleviated from supporting the body mass, and second, a launching phase, where stored energy in the ankle joint is released. Our results show a release of just a small part of the energy stored in the ankle joint during the alleviation phase. A larger impulse for the trailing leg than for the remaining body is observed during the launching phase. Here, the buckling knee joint inhibits transfer of power from the ankle to the remaining body. It appears that swing initiation profits from an impulsive ankle push-off resulting from a catapult without escapement.