Muscle spindles in nonhuman primate extrinsic auricular muscles

Muscle spindles were sought in peri-auricular muscles of several primate species (rhesus monkey, woolly monkey, and baboon). Transverse sections cut at 10 μ and stained primarily by a silver impregnation technique were examined using light microscopy. Spindles were identified on the basis of standard criteria. Posterior and/or superior auricular muscles of each species were found to contain spindles. At least some muscles innervated by facial nerve have classical spindles as component structures.     

The role of the extrinsic thoracic limb muscles in equine locomotion

Muscles have two major roles in locomotion: to generate force and to absorb/generate power (do work). Economical force generation is achieved by short-fibred pennate muscle while the maximum power output of a muscle is architecture independent. In this study we tested the hypothesis that there is an anatomical and structural separation between the force-generating anti-gravity muscles and the propulsive (limb/trunk moving) muscles of the equine forelimb. Muscle mass and fascicle length measurements were made on the thoracic limb extrinsic muscles of six fresh horse cadavers. Physiological cross-sectional area and maximum isometric force were then estimated. Maximum power was estimated from muscle volume and published contraction velocity data. The majority of extrinsic forelimb muscles were large with long fascicles arranged in parallel to the long axis of the muscle. Muscles arranged in this way are optimised for doing work. The architecture of serratus ventralis thoracis (SVT) was unique. It had short (48 +/- 17 mm) fascicles, arranged at about 45 degrees to the long axis of the muscle, which would suggest a force-generating, anti-gravity role. The muscle belly of SVT was sandwiched between two broad, thick sheets of aponeurosis. Hence, SVT could make a significant contribution to the overall elastic properties of the thoracic limb.     

The role of the extrinsic thoracic limb muscles in equine locomotion

Muscles have two major roles in locomotion: to generate force and to absorb/generate power (do work). Economical force generation is achieved by short-fibred pennate muscle while the maximum power output of a muscle is architecture independent. In this study we tested the hypothesis that there is an anatomical and structural separation between the force-generating anti-gravity muscles and the propulsive (limb/trunk moving) muscles of the equine forelimb. Muscle mass and fascicle length measurements were made on the thoracic limb extrinsic muscles of six fresh horse cadavers. Physiological cross-sectional area and maximum isometric force were then estimated. Maximum power was estimated from muscle volume and published contraction velocity data. The majority of extrinsic forelimb muscles were large with long fascicles arranged in parallel to the long axis of the muscle. Muscles arranged in this way are optimised for doing work. The architecture of serratus ventralis thoracis (SVT) was unique. It had short (48 +/- 17 mm) fascicles, arranged at about 45 degrees to the long axis of the muscle, which would suggest a force-generating, anti-gravity role. The muscle belly of SVT was sandwiched between two broad, thick sheets of aponeurosis. Hence, SVT could make a significant contribution to the overall elastic properties of the thoracic limb.     

Muscle spindles in nonhuman primate extrinsic auricular muscles.

Muscle spindles were sought in peri-auricular muscles of several primate species (rhesus monkey, woolly monkey, and baboon). Transverse sections cut at 10 mu and stained primarily by a silver impregnation technique were examined using light microscopy. Spindles were identified on the basis of standard criteria. Posterior and/or superior auricular muscles of each species were found to contain spindles. At least some muscles innervated by facial nerve have classical spindles as component structures.     

The action of extrinsic penile muscles during copulation in the male dog

Electromyographic activity of the bulbocavernosus (BC), ischiocavernosus (IC), and ischiourethral (IU) muscles was recorded during copulation in male dogs to examine the role of these muscles in the vascular engorgement process as related to the mechanisms responsible for initiating and maintaining the genital lock. In other dogs the IU muscle was severed to ascertain the influence this would have on the genital lock. No particular function in the engorgement process could be assigned to the IC muscle. Recordings from the BC muscle are consistent with the suggestion that rhythmic contraction of this muscle plays a role in pumping blood from the proximal parts of the corpus spongiosum into more distal parts of this cavernous erectile body. This would facilitate rapid engorgement of the bulbus glandis which is the structure that locks the dogs together. Recordings from the IU muscle reveal that this muscle contracts tonically just after intromission apparently also facilitating erection of the bulb by occluding venous return. Section of this muscle prevented engorgement of the bulb and eliminated the genital lock.     

The origin of extrinsic nitrergic axons supplying the human eye

Nitrergic nerve fibres of intrinsic and extrinsic origin constitute an important component of the autonomic innervation in the human eye. The intrinsic source of nitrergic nerves are the ganglion cells in choroid and ciliary muscle. In order to obtain more information on the origin of extrinsic nitrergic nerves in the human eye, we obtained superior cervical, ciliary, pterygopalatine and trigeminal ganglia from six human donors, and stained them for neuronal nitric oxide synthase (nNOS) and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-D). In the superior cervical ganglia, nNOS/NADPH-D-positive varicose axons were observed whereas perikarya were consistently negative. Fewer than 1% of perikarya in the ciliary ganglia were labelled for nNOS/NADPH-D. The diameter of nNOS/NADPH-D-positive ciliary perikarya was between 8 and 10 microm, which was markedly smaller than the diameter of the vast majority of negative perikarya in the ciliary ganglion. More than 70% of perikarya in the pterygopalatine ganglia were intensely labelled for both nNOS and NADPH-D. In trigeminal ganglia, 18% of perikarya were nNOS/NADPH-D-positive. The average diameter of trigeminal nNOS/NADPH-D perikarya was between 25 and 45 microm. Pterygopalatine and trigeminal ganglia are the most likely sources for extrinsic nerve fibres to the human eye.     

Coordination of intrinsic and extrinsic foot muscles during walking

Purpose

The human foot undergoes complex deformations during walking due to passive tissues and active muscles. However, based on prior recordings it is unclear if muscles that contribute to flexion/extension of the metatarsophalangeal (MTP) joints are activated synchronously to modulate joint impedance, or sequentially to perform distinct biomechanical functions. We investigated the coordination of MTP flexors and extensors with respect to each other, and to other ankle–foot muscles.

Methods

We analyzed surface electromyographic (EMG) recordings of intrinsic and extrinsic foot muscles for healthy individuals during level treadmill walking, and also during sideways and tiptoe gaits. We computed stride-averaged EMG envelopes and used the timing of peak muscle activity to assess synchronous vs. sequential coordination.

Results

We found that peak MTP flexor activity occurred significantly before peak MTP extensor activity during walking (P < 0.001). The period around stance-to-swing transition could be roughly characterized by sequential peak muscle activity from the ankle plantarflexors, MTP flexors, MTP extensors, and then ankle dorsiflexors. We found that foot muscles that activated synchronously during forward walking tended to dissociate during other locomotor tasks. For instance, extensor hallucis brevis and extensor digitorum brevis muscle activation peaks decoupled during sideways gait.

Conclusions

The sequential peak activity of MTP flexors followed by MTP extensors suggests that their biomechanical contributions may be largely separable from each other and from other extrinsic foot muscles during walking. Meanwhile, the task-specific coordination of the foot muscles during other modes of locomotion indicates a high-level of specificity in their function and control.

     

眼外肌手术135例的临床疗效观察

目的：探讨眼外肌手术量的设计。方法：收集本科室2003年3月-2009年3月进行眼外肌的手术病员,分析其手术并总结手术量的设计。结果：内直肌截除或后徙1mm约矫正1．5°斜视角,外直肌后徙或截除1mm约矫正1°斜视角,截除并后徙1mm约矫正3°斜视角,下直肌后徙在第一眼位为每毫米1．5°,向下注视眼位为每毫米2．5°,垂直肌后徙或缩短1mm最多矫正1．5°,一般后徙量不超过6mm,直肌截除量,内直肌7-8mm,外直肌10mm,上下直肌各6mm。结论：从临床经验中总结眼外肌手术量的设计,为今后的眼外肌手术提供参考,但眼外肌手术不能一概公式化,具体还应结合患者的实际情况和要求来设计。     

Interaction between the muscles of the neck and the extraocular muscles of the myopic eye

Summary The functional relationships between the extraocular muscles of the myopic eye and the muscles of the neck were studied by means of electromyography, with the aim of demonstrating a possible alteration of the posture of the head due to abnomal tonus of the trapezius and sternocleidomastoid mm. in subjects with defective vision. The study was conducted in a group of 10 subjects with normal vision and a group of 10 myopic subjects, between the ages of 20 and 40 years. Electromyographic recordings of the relevant muscles were made during varied eye movements. Analysis of the results demonstrated a marked difference in tonic activity of the named muscles between the myopic and the normal groups. The findings suggest that, in the correction of visual defects, attention should be paid to postural adjustment of the neck by means of a series of programmed exercises directed towards the trapezius and sternocleidomastoid mm.

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Etude EMG des interactions entre les muscles du cou et les muscles intrinsèques de l'oeil myope

Résumé Les relations fonctionnelles entre les muscles extrinsèques de l'oeil myope et les muscles du cou ont été étudiées par électromyographie, dans l'espoir de démontrer une altération éventuelle de la posture de la tête due à une anomalie du tonus des mm. trapèze et sterno-cléï-do-mastoöidien chez les patients dont la vision est mauvaise. L'étude a été menée sur 10 sujets à vision normale et 10 sujets myopes, âgés de 20 à 40 ans. Les enregistrements électromyographiques de ces muscles ont été effectués en cours de mouvements oculaires variés. L'analyse des résultats montre une difference importance dans l'activité tonique de ces muscles entre les sujets normaux et myopes. Ces constatations incitent à porter attention à l'ajustement postural du cou lors de la correction des défauts visuels, grâce à une série d'exercices programmés portant sur les mm. trapèze et sterno-cléidomastoïdien.

     

Activation of intrinsic and extrinsic finger muscles in relation to the fingertip force vector

Surface EMG was recorded from two intrinsic and two extrinsic muscles of the index finger during a two-dimensional isometric force task in the plane of flexion and extension. Subjects applied force isometrically at the fingertip in eight equally spaced directions, encompassing 360 degrees. Target forces spanned the range from 20% to 50% of maximum for each direction. The effect of varying the metacarpophalangeal (MCP) and interphalangeal (IP) joint angles was investigated. We found that when applying isometric force with the fingertip, the intrinsic muscles of the index finger behaved as a single unit whose region of activation overlapped that of the extrinsic flexor and extensor muscles. The activation region of the intrinsic muscles also spanned a range of force directions for which the extrinsic muscles were virtually inactive. The activation of all muscles, with the exception of the extrinsic extensor, was modified by changing the MCP and IP joint angles. Both IP flexion and MCP extension produced rotation of the resultant activity vector in the direction of MCP flexion. However, the relative rotation was much greater with IP flexion than MCP extension. The effect of IP flexion is linked to rotation of the force direction where joint torque switches from extension to flexion, while the effect of MCP extension is more likely related to changes in muscle length and MCP moment arm. Our results suggest that the primary role of intrinsic finger muscles is to precisely control the direction of fingertip force, while extrinsic muscles provide stability of the joints.     

Periodic modulation of motor-unit activity in extrinsic hand muscles during multidigit grasping

We recently examined the extent to which motor units of digit flexor muscles receive common input during multidigit grasping. This task elicited moderate to strong motor-unit synchrony (common input strength, CIS) across muscles (flexor digitorum profundus, FDP, and flexor pollicis longus, FPL) and across FDP muscle compartments, although the strength of this common input was not uniform across digit pairs. To further characterize the neural mechanisms underlying the control of multidigit grasping, we analyzed the relationship between firing of single motor units from these hand muscles in the frequency domain by computing coherence. We report three primary findings. First, in contrast to what has been reported in intrinsic hand muscles, motor units belonging to different muscles and muscle compartments of extrinsic digit flexors exhibited significant coherence in the 0- to 5- and 5- to 10-Hz frequency ranges and much weaker coherence in the higher 10-20 Hz range (maximum 0.0025 and 0.0008, respectively, pooled across all FDP compartment pairs). Second, the strength and incidence of coherence differed considerably across digit pairs. Third, contrary to what has been reported in the literature, across-muscle coherence can be stronger and more prevalent than within-muscle coherence, as FPL-FDP2 (thumb-index digit pair) exhibited the strongest and most prevalent coherence in our data (0.010 and 43% at 3 Hz, respectively). The heterogeneous organization of common input to these muscles and muscle compartments is discussed in relation to the functional role of individual digit pairs in the coordination of multiple digit forces in grasping.