scholarly journals Muscle Spindle Density of Lateral Rotators of the Thigh in Japanese Macaques and a Gibbon

2019 ◽  
Vol 208 (1-2) ◽  
pp. 1-12
Author(s):  
Sawa Takeuchi ◽  
Eishi Hirasaki ◽  
Hiroo Kumakura
Keyword(s):  
Muscle Spindle ◽  
Hip Joint ◽  
Muscle Length ◽  
Muscle Spindles ◽  
Functional Differentiation ◽  
Japanese Macaques ◽  
Obturator Externus ◽  
Obturator Internus ◽  
Obturator Internus Muscle ◽  
Species Specific

We examined the six small lateral rotators of the hip joint, which is one of the most flexible joints and allows kinematically complex motions of the hindlimb, to elucidate the functional differentiation among these muscles and to test the hypothesis that species-specific characteristics in hindlimb use during locomotion are reflected in the muscle spindle density and in other parameters of the deep small hip joint rotators. For these purposes, we estimated the number of muscle spindles of the superior gemellus muscle (SG), inferior gemellus muscle, quadratus femoris muscle, obturator internus muscle (OI), obturator externus muscle, and piriformis muscle in three Japanese macaques and a gibbon, using 30-µm-thick serial sections throughout each muscle length after azan staining. The numbers of muscle spindles per 10,000 muscle fibers were determined to compare inter-muscle variation. The spindle density was highest in the SG and lowest in the OI in the Japanese macaques, suggesting that the SG, which is attached to the tendon of the OI, functions as a kinesiological monitor of the OI. On the other hand, SG the was missing in the gibbon, and the OI in the gibbon contained more spindles than that in the Japanese macaques. This suggests that the SG and the OI fused into one muscle in the gibbon. We postulate that the relative importance of the deep small hip rotator muscles differs between the Japanese macaques and gibbon and that the gibbon’s muscles are less differentiated in terms of the spindle density, probably because this brachiating species uses its hindlimbs less frequently.

scholarly journals Position Sensitivity of Feline Paraspinal Muscle Spindles to Vertebral Movement in the Lumbar Spine

2009 ◽  
Vol 101 (4) ◽  
pp. 1722-1729 ◽  
Author(s):  
Dong-Yuan Cao ◽  
Joel G. Pickar ◽  
Weiginq Ge ◽  
Allyson Ianuzzi ◽  
Partap S. Khalsa
Keyword(s):  
Lumbar Spine ◽  
Muscle Spindle ◽  
Facet Joint ◽  
Spinous Process ◽  
Muscle Length ◽  
Muscle Spindles ◽  
Paraspinal Muscle ◽  
High Position ◽  
Position Sensitivity ◽  
The Relationship

Muscle spindles contribute to sensorimotor control by supplying feedback regarding muscle length and consequently information about joint position. While substantial study has been devoted to determining the position sensitivity of spindles in limb muscles, there appears to be no data on their sensitivity in the low back. We determined the relationship between lumbar paraspinal muscle spindle discharge and paraspinal muscle lengthening estimated from controlled cranialward movement of the L6 vertebra in anesthetized cats. Ramp (0.4 mm/s) and hold displacements (0.2, 0.4, 0.6, 0.8, and 1.2 mm for 2.5 s) were applied at the L6 spinous process. Position sensitivity was defined as the slope of the relationship between the estimated increase in muscle length and mean instantaneous frequency at each length. To enable comparisons with appendicular muscle spindles where joint angle was measured, we also calculated sensitivity in terms of the L6 and L7 intervertebral flexion angle (IVA). This angle was estimated from measurements of facet joint capsule strain (FJC) based on a previously established relationship between IVA and FJC strain in the cat lumbar vertebral column during lumbar flexion. Single-unit recordings were obtained from 12 muscle spindle afferents. Longissimus and multifidus muscles contained the receptive field of 10 and 2 afferents, respectively. Mean position sensitivity was 16.3 imp·s−1·mm−1 [10.6–22.1, 95% confidence interval (CI), P < 0.001]. Mean angular sensitivity was 5.2 imp·s−1·°−1 (2.6–8.0, P < 0.003). These slope estimates were more than 3.5 times greater compared with appendicular muscle spindles, and their CIs did not contain previous slope estimates for the sensitivity of appendicular spindles from the literature. Potential reasons for and the significance of the apparently high position sensitivity in the lumbar spine are discussed.

scholarly journals Muscle spindles in human tibialis anterior encode muscle fascicle length changes

2017 ◽  
Vol 117 (4) ◽  
pp. 1489-1498 ◽  
Author(s):  
James Day ◽  
Leah R. Bent ◽  
Ingvars Birznieks ◽  
Vaughan G. Macefield ◽  
Andrew G. Cresswell
Keyword(s):  
Muscle Spindle ◽  
Tibialis Anterior ◽  
Tibialis Anterior Muscle ◽  
Muscle Length ◽  
Muscle Spindles ◽  
Muscle Spindle Afferents ◽  
Fascicle Length ◽  
Muscle Fascicle ◽  
Length Changes

Muscle spindles provide exquisitely sensitive proprioceptive information regarding joint position and movement. Through passively driven length changes in the muscle-tendon unit (MTU), muscle spindles detect joint rotations because of their in-parallel mechanical linkage to muscle fascicles. In human microneurography studies, muscle fascicles are assumed to follow the MTU and, as such, fascicle length is not measured in such studies. However, under certain mechanical conditions, compliant structures can act to decouple the fascicles, and, therefore, the spindles, from the MTU. Such decoupling may reduce the fidelity by which muscle spindles encode joint position and movement. The aim of the present study was to measure, for the first time, both the changes in firing of single muscle spindle afferents and changes in muscle fascicle length in vivo from the tibialis anterior muscle (TA) during passive rotations about the ankle. Unitary recordings were made from 15 muscle spindle afferents supplying TA via a microelectrode inserted into the common peroneal nerve. Ultrasonography was used to measure the length of an individual fascicle of TA. We saw a strong correlation between fascicle length and firing rate during passive ankle rotations of varying rates (0.1–0.5 Hz) and amplitudes (1–9°). In particular, we saw responses observed at relatively small changes in muscle length that highlight the sensitivity of the TA muscle to small length changes. This study is the first to measure spindle firing and fascicle dynamics in vivo and provides an experimental basis for further understanding the link between fascicle length, MTU length, and spindle firing patterns. NEW & NOTEWORTHY Muscle spindles are exquisitely sensitive to changes in muscle length, but recordings from human muscle spindle afferents are usually correlated with joint angle rather than muscle fascicle length. In this study, we monitored both muscle fascicle length and spindle firing from the human tibialis anterior muscle in vivo. Our findings are the first to measure these signals in vivo and provide an experimental basis for exploring this link further.

scholarly journals Impacts of external rotators and the ischiofemoral ligament on preventing excessive internal hip rotation: a cadaveric study

2022 ◽  
Vol 17 (1) ◽  
Author(s):  
Kazuyoshi Baba ◽  
Daisuke Chiba ◽  
Yu Mori ◽  
Yoshiyuki Kuwahara ◽  
Atsushi Kogure ◽  
...  
Keyword(s):  
Internal Rotation ◽  
Circular Plate ◽  
Hip Joint ◽  
Joint Rotation ◽  
Rotation Direction ◽  
Obturator Externus ◽  
Obturator Internus ◽  
The Right ◽  
Hip Flexion ◽  
External Rotator

Abstract Background This study examined the biomechanics of preventing excessive internal hip joint rotation related to the hip flexion angle. Method An intramedullary nail with a circular plate equipped with a protractor was installed in the femur of nine normal hips. The circular plate was pulled by 3.15 Nm of force in the internal rotation direction. The external rotators were individually resected, finally cutting the ischiofemoral ligament. The cutting order of the external rotators differed on each side to individually determine the internal rotation resistance. The external rotators were resected from the piriformis to the obturator externus in the right hips and the reverse order in the left hips. Traction was performed after excising each muscle and ischiofemoral ligament. Measurements were taken at 0°, 30°, and 60° of hip flexion, and the differences from baseline were calculated. Results For the right hip measurements, the piriformis and ischiofemoral ligament resection significantly differed at 0° of flexion (p = 0.02), each external rotator and the ischiofemoral ligament resections significantly differed at 30° of flexion (p < 0.01), and the ischiofemoral ligament and piriformis and inferior gemellus resections significantly differed at 60° of flexion (p = 0.04 and p = 0.02, respectively). In the left hips, the ischiofemoral ligament and obturator externus, inferior gemellus, and obturator internus resections significantly differed at 0° of flexion (p < 0.01, p < 0.01, and p = 0.01, respectively), as did each external rotator and the ischiofemoral ligament resections at 30° of flexion (p < 0.01). Conclusion The ischiofemoral ligament primarily restricted the internal rotation of the hip joint. The piriformis and obturator internus may restrict internal rotation at 0° and 60° of flexion.

Activity patterns in individual hindlimb primary and secondary muscle spindle afferents during normal movements in unrestrained cats

1979 ◽  
Vol 42 (2) ◽  
pp. 420-440 ◽  
Author(s):  
G. E. Loeb ◽  
J. Duysens
Keyword(s):  
Muscle Spindle ◽  
Activity Patterns ◽  
Muscle Length ◽  
Muscle Spindle Afferents ◽  
General Observation ◽  
Postural Changes ◽  
Motor Activities ◽  
Specific Muscle ◽  
Length Changes ◽  
Rapid Modulation

1. Chronically implanted microelectrode wires in the L7 and S1 dorsal root ganglia were used to record unit activity from cat hindlimb primary and secondary muscle spindle afferents. Units could be reliably recorded for several days, permitting comparison of their activity with homonymous muscle EMG and length during a variety of normal, unrestrained movements. 2. The general observation was that among both primary and secondary endings there was a broad range of different patterns of activity depending on the type of muscle involved and the type of movement performed. 3. During walking, the activity of a given spindle primary was usually consistent among similar step cycles. However, the activity was usually poorly correlated with absolute muscle length, apparently unrealted to velocity of muscle stretch, and could change markedly for similar movements performed under different conditions. 4. Spindle activity modulation not apparently related to muscle length changes was assumed to be influenced by fusimotor activity. In certain muscles, this presumption leads to the conclusion that gamma-motoneurons may be activated out of phase with homonymous alpha-motoneurons as well as by more conventional alpha-gamma-motoneuron coactivation. 5. Simultaneous recordings of two spindle primary afferents from extensor digitorum longus indicated that spindles within the same muscle may differ considerably with respect to this presumed gamma-motoneuron drive. 6. Spindle secondary endings appeared to be predominantly passive indicators of muscle length during walking, but could demonstrate apparently strong fusimotor modulation during other motor activities such as postural changes and paw shaking. 7. Both primary and secondary endings were observed to undergo very rapid modulation of firing rates in response to presumed reflexly induced intrafusal contractions. 8. It is suggested that the pattern of fusimotor control of spindles may be tailored to the specific muscle and task being performed, rather than necessarily dominated by rigid alpha-gamma coactivation.

scholarly journals Firing properties of muscle spindles supplying the intrinsic foot muscles of humans in unloaded and freestanding conditions

2019 ◽  
Vol 121 (1) ◽  
pp. 74-84 ◽  
Author(s):  
T. P. Knellwolf ◽  
A. R. Burton ◽  
E. Hammam ◽  
V. G. Macefield
Keyword(s):  
Muscle Spindle ◽  
Postural Sway ◽  
Center Of Pressure ◽  
Muscle Spindles ◽  
Medial Malleolus ◽  
Proprioceptive Information ◽  
Muscle Spindle Afferents ◽  
Tungsten Microelectrode ◽  
Firing Properties ◽  
Intrinsic Muscles

We recently developed an approach for recording from muscle spindles in the intrinsic muscles of the foot in freestanding humans by inserting a tungsten microelectrode into the posterior tibial nerve behind the medial malleolus of the ankle. Here we characterize the behavior of muscle spindles in the small muscles of the foot in 1) seated subjects with the leg horizontal and the foot naturally plantarflexed and 2) standing subjects. In the first study, recordings were made from 26 muscle spindle afferents located within flexor digiti minimi brevis ( n = 4), abductor digiti minimi ( n = 3), quadratus plantae ( n = 3), plantar interossei ( n = 4), flexor digitorum brevis ( n = 3), dorsal interossei ( n = 2), and lumbricals ( n = 2), with one each supplying abductor hallucis, adductor hallucis, and flexor hallucis brevis. The identity of another two muscle afferents was unknown. The majority of the units were silent at rest, only seven (27%) being spontaneously active. Because of the anatomic constraints of the foot, some spindles supplying muscles acting on the toes responded to movements of one or more digits. In the second study, 12 muscle spindle afferents were examined during standing. The ongoing discharge of eight spindle afferents covaried with changes in the center of pressure during postural sway. We conclude that the majority of spindle endings in the small muscles of the foot are silent at rest, which may allow them to encode changes in conformation of the foot when it is loaded during standing. Moreover, these muscle spindle afferents can provide useful proprioceptive information during standing and postural sway. NEW & NOTEWORTHY We have characterized the firing properties of muscle spindles in the intrinsic muscles of the human foot for the first time. The majority of the spindle endings are silent in seated subjects, and most fire tonically during standing, their discharge covarying with center of pressure during postural sway. We conclude that spindle endings in the intrinsic muscles of the foot provide useful proprioceptive information during free standing.

scholarly journals Effects of tonic muscle pain on fusimotor control of human muscle spindles during isometric ankle dorsiflexion

2019 ◽  
Vol 121 (4) ◽  
pp. 1143-1149
Author(s):  
Lyndon J. Smith ◽  
Vaughan G. Macefield ◽  
Ingvars Birznieks ◽  
Alexander R. Burton
Keyword(s):  
Muscle Spindle ◽  
Muscle Pain ◽  
Tibialis Anterior Muscle ◽  
Muscle Spindles ◽  
Muscle Spindle Afferents ◽  
Firing Rates ◽  
Leg Muscles ◽  
Tonic Muscle ◽  
Voluntary Contractions ◽  
Ankle Dorsiflexors

Studies on anesthetized animals have revealed that nociceptors can excite fusimotor neurons and thereby change the sensitivity of muscle spindles to stretch; such nociceptive reflexes have been suggested to underlie the mechanisms that lead to chronic musculoskeletal pain syndromes. However, the validity of the “vicious cycle” hypothesis in humans has yielded results contrasting with those found in animals. Given that spindle firing rates are much lower in humans than in animals, it is possible that some of the discrepancies between human experimental data and those obtained in animals could be explained by differences in background fusimotor drive when the leg muscles are relaxed. We examined the effects of tonic muscle pain during voluntary contractions of the ankle dorsiflexors. Unitary recordings were obtained from 10 fusimotor-driven muscle spindle afferents (6 primary, 4 secondary) supplying the ankle dorsiflexors via a microelectrode inserted percutaneously into the common peroneal nerve. A series of 1-min weak contractions was performed at rest and during 1 h of muscle pain induced by intramuscular infusion of 5% hypertonic saline into the tibialis anterior muscle. We did not observe any statistically significant increases in muscle spindle firing rates of six afferents followed during tonic muscle pain, although discharge variability increased slightly. Furthermore, a participant’s capacity to maintain a constant level of force, while relying on proprioceptive feedback in the absence of visual feedback, was not compromised during pain. We conclude that nociceptive inputs from contracting muscle do not excite fusimotor neurons during voluntary isometric contractions in humans. NEW & NOTEWORTHY Data obtained in the cat have shown that muscle pain causes a marked increase in the firing of muscle spindles, attributed to a nociceptor-driven fusimotor reflex. However, our studies of muscle spindles in relaxed leg muscles failed to find any effect on spindle discharge. Here we showed that experimental muscle pain failed to increase the firing of muscle spindle afferents during weak voluntary contractions, when fusimotor drive sufficient to increase their firing is present.

Piriformis Syndrome and Other Nerve Entrapments of the Posterior Pelvis

2018 ◽  
Author(s):  
Aaron G. Filler
Keyword(s):  
Peripheral Nerve Injury ◽  
Pudendal Nerve ◽  
Cauda Equina ◽  
Piriformis Syndrome ◽  
Piriformis Muscle ◽  
Spinal Nerves ◽  
Nerve Entrapments ◽  
Obturator Internus ◽  
Surgical Options ◽  
Obturator Internus Muscle

Not every case of neurologically based pelvic/genital numbness/incontinence is due to cauda equina syndrome. Pelvic pain, incontinence, and sexual dysfunction can result from treatable peripheral nerve injury or entrapment affecting the pudendal nerves or impar ganglion. Learning the signs, physical exam findings, tests, and surgical options greatly expands a neurosurgeon’s range. The pudendal nerve and nerve to the obturator internus muscle arise after S2, S3, and S4 spinal nerves traverse the piriformis muscle. They exit the sciatic notch with the sciatic nerve but then re-enter the pelvis, where the pudendal nerve then gives off bladder, rectal, and genital branches.

scholarly journals The effects of vibration-induced altered stretch reflex sensitivity on maximal motor unit firing properties

2019 ◽  
Vol 121 (6) ◽  
pp. 2215-2221 ◽  
Author(s):  
Alejandra Barrera-Curiel ◽  
Ryan J. Colquhoun ◽  
Jesus A. Hernandez-Sarabia ◽  
Jason M. DeFreitas
Keyword(s):  
Motor Unit ◽  
Muscle Spindle ◽  
Stretch Reflex ◽  
Muscle Spindles ◽  
Motor Unit Action Potential ◽  
Firing Rates ◽  
Motor Unit Firing ◽  
Firing Properties ◽  
Spindle Function ◽  
Voluntary Strength

It is well known that muscle spindles have a monosynaptic, excitatory connection with α-motoneurons. However, the influence of muscle spindles on human motor unit behavior during maximal efforts remains untested. It has also been shown that muscle spindle function, as assessed by peripheral reflexes, can be systematically manipulated with muscle vibration. Therefore, the purpose of this study was to analyze the effects of brief and prolonged vibration on maximal motor unit firing properties. A crossover design was used, in which each of the 24 participants performed one to three maximal knee extensions under three separate conditions: 1) control, 2) brief vibration that was applied during the contraction, and 3) after prolonged vibration that was applied for ~20 min before the contraction. Multichannel EMG was recorded from the vastus lateralis during each contraction and was decomposed into its constituent motor unit action potential trains. Surprisingly, an approximate 9% reduction in maximal voluntary strength was observed not only after prolonged vibration but also during brief vibration. In addition, both vibration conditions had a large, significant effect on firing rates (a decrease in the rates) and a small to moderate, nonsignificant effect on recruitment thresholds (a small increase in the thresholds). Therefore, vibration had a detrimental influence on both maximal voluntary strength and motor unit firing properties, which we propose is due to altered function of the stretch reflex pathway. NEW & NOTEWORTHY We used vibration to alter muscle spindle function and examined the vibration’s influence on maximal motor unit properties. We discovered that vibration had a detrimental influence on motor unit behavior and motor output by decreasing motor unit firing rates, increasing recruitment thresholds, which led to decreased maximal strength. We believe that understanding the role of muscle spindles during maximal contractions provides a deeper insight into motor control and sensorimotor integration.

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