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Cranial Neuropathies I, V, and VII–XII
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
This is a monosynaptic myotatic reflex in which the trigeminal nerve constitutes both the afferent limb (sensory division of V3) and the efferent limb (motor division of V3) of the reflex arc. Its first-order neuron is not in the gasserian ganglion, but located centrally in the mesencephalic nucleus in the midbrain: Afferent limb: Ia fibers in V3 division that carry proprioceptive sensory information from facial muscles and masseter. Collateral fibers synapse with the motor nucleus of CN V.Efferent limb: mandibular fibers that originate in the motor nucleus of CN V. Efferent (motor) fibers are sent to masticatory muscles via the motor division of V3.
Spinal Cord and Reflexes
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
Also known as the inverse myotatic reflex and autogenic inhibition, the reflex arc comprises the Golgi tendon organs (GTOs) as the receptors (Section 9.4.1), Ib afferent fibers terminating on Ib-interneurons, the α-motoneurons of the homonymous muscle, and the muscle itself, as illustrated in Figure 11.10. The Ib afferents excite Ib-interneurons that inhibit α-motoneurons, making the reflex disynaptic. As in the case of the stretch reflex, the effect of the sensory fibers, which is inhibitory in this case, is exerted on synergist muscles as well, and inhibition of the α-motoneurons of the agonist muscles leads to excitation of the α-motoneurons of the antagonist muscles. This occurs through excitation by Ib fibers of excitatory interneurons that excite the α-motoneurons of the antagonist muscles, and is an example of reciprocal innervation, a special case of which being reciprocal inhibition.
Non-Synonyms (Similar-Sounding)
Published in Terence R. Anthoney, Neuroanatomy and the Neurologic Exam, 2017
Stretch reflex-2 (Heim, p. 158): A clinical entity, elicited by a sudden lengthening of a muscle, as by tapping its tendon with a reflex hammer. Also known as the “myotatic reflex,” it corresponds to just the phasic component of the physiologic stretch reflex described above. See, also, SS: Brisk knee jerk.
Solution space: Monitoring the dynamics of motor rehabilitation
Published in Physiotherapy Theory and Practice, 2019
Jurjen Bosga, Wim Hullegie, Robert van Cingel, Ruud Meulenbroek
This analysis provides insight into the relative involvement of the various motor control processes, for instance by allowing the distinction of the extremely rapid myotatic reflex activity (i.e. physiological tremors) and the more slowly evolving visual and even slower cognitive monitoring processes. A particularly relevant PSD index for the solution space is the slope function (ß), which allows the quantification of the relative contributions of the different control processes in a particular motor pattern (Duarte and Zatsiorsky, 2001; Harrison and Stergiou, 2015). If ß is 0, this indicates that lower- and higher-frequency control processes have contributed equally to the production of the movement. A ß value < 0 reflects a systematic damping of the higher frequencies, denoting a relative decline in fast adaptive processes (e.g. physiological tremor, myotatic, or crossed reflexes) that contribute to movement execution. Accordingly, the smaller the negative value ß is, the stronger the contribution of the relatively slower control processes (e.g. visuomotor feedback) to the production of movement. In this article we use ß as a relative measure, that is, to indicate whether control processes were relatively slower or faster compared to previous measurements. Since ß as a relative measure is additive, we calculated the mean ß value of the three movement directions of each body segment. Next, we computed the absolute value of ß, subsequently denoted as |ß|. We used |ß| to facilitate reading, as higher absolute beta values represent more visual and cognitive control.
A historical review of the evolution of the Tardieu Scale
Published in Brain Injury, 2018
Susan Louisa Morris, Gavin Williams
Two further additions were made by Held and Pierrot-Deseilligny. The first addition relates to their ‘fifth principle’, the necessity to maintain consistency in variables that are known to impact on spasticity such as time of the day, body position with or without support, position of other limb segments with particular thought given to the neck (16). The second addition provided a more accurate characterization of the less rapid (regular) of Tardieu’s stretch velocities. They proposed that the limb segment fall under the influence of gravity (which is an acceleration not a velocity) and it was assigned V2, while the slow velocity (below the threshold for triggering a myotatic reflex) was V1, and the fastest velocity was V3 (16). Held and Pierrot-Deseilligny encouraged the use of V2 because of its obvious advantage of being perfectly reproducible across examiners and test sessions (16).
The Impact of Segmental Trunk Support on Posture and Reaching While Sitting in Healthy Adults
Published in Journal of Motor Behavior, 2018
Victor Santamaria, Jaya Rachwani, Wayne Manselle, Sandra L. Saavedra, Marjorie Woollacott
Last, the ipsilateral cervical and contralateral thoracic muscles displayed earlier muscle onsets during the CPA stage with an external support at midribs level. This could be due in part to a restriction in the number of trunk segments and inertial properties to be controlled and thus the execution of a quicker muscle response mediated by feedback mechanisms after reaching initiation (Santos et al., 2010a, 2010b). Regarding this mechanism, the time-latency response of the paraspinal muscles (∼200 ms) suggest that feedback responses are likely mediated via the automatic posture-control system rather than short-loop reflexive circuits (e.g., myotatic reflex; Horak & Nashner, 1986; Tresilian, 2012). This observation is an important aspect of control to consider in neurological conditions. For example, people with stroke and cerebellar disorders display neuromuscular deficits, including onset delays and dyssynchrony of trunk muscles that consequently affect the temporal recruitment order that contributes to effective posture during activities of daily living (Bruttini et al., 2014; Dickstein, Shefi, Marcovitz, & Villa, 2004; Diedrichsen, Verstynen, Lehman, & Ivry, 2005; Winzeler-Merçay & Mudie, 2002).