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Muscle Fiber Types
Published in Charles Paul Lambert, Physiology and Nutrition for Amateur Wrestling, 2020
A motor nerve, and the muscle fibers it connects to (innervates), is called a motor unit. The motor nerves vary in size from the smallest that are slow twitch oxidative, medium are FOG fibers, and fast twitch glycolytic fibers are the largest. Motor unit recruitment or engaging the different muscle fibers follows the size principle (McComas 1996). With increasing force of contraction the larger motor neurons are recruited. During low force contractions the slow twitch oxidative fibers are recruited, during higher force contractions the FOG fibers in addition to the slow twitch oxidative fibers are recruited, and during the highest force contractions the fast twitch glycolytic fibers are also recruited. So force dictates the degree of motor unit recruitment. The higher the force, the greater the number of motor units and the number of fast twitch fibers recruited. Speed of contraction has little to do with motor unit recruitment. That is, at fast contraction velocities (speeds) with little force, only slow twitch fibers are recruited (McComas 1996). Once force is increased, more motor units and the fast twitch fibers starting with the fast twitch oxidative glycolytic get recruited. Last, at maximal forces all motor units are recruited including the fast twitch glycolytic, FOG, and slow twitch oxidative fibers (Henneman 1979).
Epstein–Barr virus and the nervous system
Published in Avindra Nath, Joseph R. Berger, Clinical Neurovirology, 2020
Alexandros C. Tselis, Kumar Rajamani, Pratik Bhattacharya
Other forms of peripheral nerve involvement have been reported in conjunction with EBV infection. Lumbosacral radiculoplexopathy with pain and lower extremity weakness has been reported in five patients. In all cases, pain (in the gluteal area and the thigh) was an early complaint, followed by leg weakness, which was severe enough for the patients to require ambulatory assistance, two being wheelchair-bound. All patients recovered completely or nearly completely. Electromyography showed acute denervation and mild slowing of motor nerve conduction. Serology showed acute EBV infection in all patients. Cerebrospinal fluid was examined in the five patients and showed mild elevation in protein in three and a very mild pleocytosis in two. Two patients received oral prednisone and seemed to improve on it. All patients were independently ambulatory several months after onset [44]. Infectious mononucleosis has also preceded brachial plexopathy. In one case, a 19-year-old man developed acute pain in the shoulders about 2 weeks after developing infectious mononucleosis, diagnosed by a positive heterophile test. Several days later, he was unable to lift his arms above his head, and he developed atrophy of the shoulder girdle muscles. Electromyography showed bilateral brachial plexopathy. Complete recovery occurred over the next 4 months [45]. Another patient developed a bilateral brachial plexopathy with pain and weakness of the arms, along with a unilateral Bell’s palsy, about a week after febrile pharyngitis. Infectious mononucleosis was diagnosed by a positive heterophile test [46].
Hands
Published in Tor Wo Chiu, Stone’s Plastic Surgery Facts, 2018
In general, in terms of outcomes after BPI/surgery, Better outcomes in the young.Better prognosis with distal lesions.Better outcomes for infraganglionic lesions over root avulsions.Motor nerve transfers are usually better than nerve grafts.
Anatomical and functional identification of the external branch of the superior laryngeal nerve: classification based on morphology and electrophysiological monitoring
Published in Acta Chirurgica Belgica, 2022
Uncomplicated thyroid surgery urges the preservation of anatomical integrity of the motor nerves wherein the anatomical exposure of the RLNs is mandatory for its intactness. It is often difficult for surgeons to visualize the EBSLNs in all patients unlike the RLN that is easily identifiable and exposable by experienced thyroid surgeons. The past authors have reported that the distal portion of the EBSLNs runs deep into the pharyngeal constrictor muscle fibers before reaching the CTM in 15–20% of the patients [8,9]. On the other hand, the visual integrity of nerve branches does not always guarantee appropriate motor functions. Intraoperative neuromonitoring (IONM) is employed to evaluate the motor activity of nerve branches and has gained widespread acceptance as an adjunct for the anatomical identification [10–15]. Some previous studies have demonstrated that the electrophysiological detection of the EBSLNs by IONM can significantly contribute to the anatomical identification of these thin motor branches [1,2,16,17]. Accordingly, the anatomic and electrophysiological characteristics of the motor nerve have been established under various subtitles. We thus hypothesized that nerve monitoring would provide additional findings for the identification and function of the EBSLN during thyroid surgery. Thus, the results of our anatomical and neuromonitoring processes were classified under separate types of identification and motor activities.
A computational model of upper airway respiratory function with muscular coupling
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Olusegun J. Ilegbusi, Don Nadun S. Kuruppumullage, Matthew Schiefer, Kingman P. Strohl
For the genioglossus (the major upper airway dilator muscle), we assumed that muscle contraction occurred for 3s along an anterior-posterior direction. The strength of the contraction was induced through a time-force function in the FE model. In reality, the contraction of muscle tissues is activated through impulses delivered through the motor nerve network, for instance, the hypoglossal nerve for genioglossus in the tongue (Eisele et al. 1997; Yoo and Durand 2005). Figure 3 shows the activation profile used in this study. The activation duration was chosen to mirror a typical neurostimulation procedure. The magnitude of the force at this stage was chosen through preliminary simulations with varying forces until a profile produced airway openings at the epiglottis level typically observed in trial applications of neurostimulation. The activation profile was used as a distributed load within the region of genioglossus muscle. We assumed the airway structure was initially at rest. Therefore, there was no activation for the first 3s of the simulation in order to allow the airway structure to reach stable condition under gravity in the lateral-posterior direction.
Neutrophil peptide-1 promotes the repair of sciatic nerve injury through the expression of proteins related to nerve regeneration
Published in Nutritional Neuroscience, 2022
Fei Yu, Yusong Yuan, Hailin Xu, Suping Niu, Na Han, Yajun Zhang, Xiaofeng Yin, Yuhui Kou, Baoguo Jiang
Six weeks after operation, rats were sacrificed via intraperitoneal injection of 1% pentobarbital sodium (30 mg/kg), the right sciatic nerve of the rats was exposed at the clamp, and the nerve conduction velocities of the tibial and common peroneal nerve were measured after repair. Stimulating electrodes were placed at two points far from the clamp, and recording electrodes were inserted into the middle of the corresponding innervating muscles. The motor nerve conduction velocity was measured by the muscle compound action potential method. The following electrical stimulation parameters of the Synergy electrophysiology instrument (Oxford, USA) were set: square-wave stimulation intensity of 0.9 mA, wave width of 0.1 ms, and frequency of 1 Hz. Compound muscle action potentials were recorded. The latency of compound muscle action potentials obtained through stimulation of the distal and proximal nerve trunks was recorded; the difference (dt) between the two latency periods was calculated; the length of nerve trunks (dl) between the distal and proximal stimulating points was measured; and the motor nerve conduction velocity was calculated as follows: V = dl/dt [17].