Diss. (sammanfattning) Umeå : Univ., 2004. / Härtill 4 uppsatser.

The somatosensory system has been implicated in the compensatory response of the nervous system to postural perturbations in humans and cats. The approach elicited - dubbed the Force Constraint Strategy - through a possible combined action of proprioceptive and cutaneous feedback, determines, and adjusts for, horizontal disturbances in various directions of a supporting surface. To understand the mechanisms underlying this strategy, we asked whether the response patterns of muscle proprioceptors correspond to those of electromyographic recordings (EMG) in the aforementioned Force Constraint experiments. The mechanical properties of the musculoskeletal system may also play a role in the restoration of stability. Thus, we also hypothesize that a proximal muscle would be relatively tightly tuned spatially whereas the distal muscle would exhibit a more diffuse spatial response distribution. To this end we selected the medial gastrocnemius (MG) and biceps femoris (BF) muscles to serve as our proximal and distal models respectively. Cats anesthetized using pentobarbital were set in a stereotaxic frame with the right leg positioned on a servo-controlled platform. The platform was shifted horizontally in 16 different directions according to a ramp-and-hold waveform. Intra-axonal recordings of activity from Ia afferents of BF and MG muscles were taken. Results indicate that the strategy makes use of information from the muscle proprioceptors. However, there is no differential response in tuning breadth with respect to muscle architecture. By characterizing the role of muscle proprioceptors in the mediation of corrective responses to perturbations of balance and stability, the results from this experiment can be used to verify biomechanical models, as well as further elucidate the underlying mechanisms of motor control.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (p. 100-111).

This thesis is an investigation of the role of skin and muscle receptors in proprioception at the ankle joint in humans. Somatosensory afferents provide the central nervous system with cues that code for movement and position of the segments, senses collectively known as proprioception. Intramuscular receptors, in particular muscle spindles, code for length and movement velocity of muscles surrounding a joint and therefore play an integral role in proprioception. The role of cutaneous receptors is less clear. When activated via skin stretch they create illusory movements of the limbs, and they are capable of responding to movements of the joints. To what extent these cues are utilized over and above input from muscle spindles remains unknown. In addition, there is evidence that cutaneous receptors may influence the sensitivity of muscle spindles by modulating their level of fusimotor activation. The aim of this thesis was to further examine the role of skin in proprioception and to determine whether or not skin of the foot and ankle is capable of modulating fusimotor drive to muscle spindles of the lower limb. The current thesis is comprised of three studies. The first experiment utilized a matching task at the ankle joint and determined that skin from the dorsum of the foot and ankle is necessary for accurate proprioception. The remaining two experiments used the technique of microneurography to record from single nerve afferents in awake, human participants. Initially, cutaneous afferents were isolated and recorded to determine the efficacy of using cooling over their receptive field as a method to decrease their sensitivity and output. Once cooling was established as an effective tool, the final experiment isolated and recorded from muscle spindles in response to passive, ramp and hold movements at the ankle. It was determined that a reduction in skin input (via cooling) altered the firing response of a portion of spindles. It is likely that this change in firing was due to modulation of fusimotor drive to the spindles. Collectively, the current work contributes the novel findings that skin on the dorsum of the foot is necessary for accurate proprioception at the ankle and that this is largely due to the role of skin as an independent proprioceptive channel. In addition, we have shown for the first time that a reduction in skin input from the foot dorsum is capable of modulating spindle discharge during a passive ramp and hold movement at the ankle, demonstrating a minor role for this interaction in proprioception. A secondary finding of the thesis was that cooling with ice is an effective tool for reducing input from all four classes of cutaneous mechanoreceptors.

Diss. (sammanfattning) Umeå : Univ., 2009. / Härtill 3 uppsatser.

The muscle spindle is invested by a capsule of continuous, multilayered perineural epithelium, creating a periaxial space around the intrafusal muscle fibres and their innervation. The ultrastructural permeability of the muscle spindle capsule was assessed in anterior tibialis muscles of adult mice after systemic injection of the exogenous protein tracer, horseradish peroxidase (HRP). After varying time intervals ranging from 2 to 240 minutes, anesthetized animals were systemically perfused with fixative. Muscles were then removed and processed by routine cytochemical methods in order to demonstrate the distribution of peroxidase activity. While bare capillaries were never encountered within the intracapsular periaxial space of the muscle spindle, they frequently and intimately abut against its outer perineural capsule. Two minutes after injection of HRP, reaction product was localized in capillary endothelial plasmalemmal vesicles, just prior to its accumulation in the tissue space immediately surrounding the subjacent capsular perineurium in the equatorial region. In the polar region of the muscle spindle capsule, however, there was evidence of reaction product in the periaxial space at the same two minute time period. Ten minutes after administration of the tracer, a small population of perineural vesicles contained HRP. At the 12.5 minute interval, the sarcolemmae and T-tubules of polar intrafusal muscle fibres were subsequently labelled. Equatorial (sensory) regions of muscle spindles appeared to be relatively less permeable to the entrance of the tracer than more distal polar regions. By 15 minutes post-injection, HRP was seen traversing the perineural capsule in equatorial zones; and by 30 minutes, perineural and Schwann cell phagocytosis of the exogenous protein was extensive. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate

Thesis (M.S.)--University of Michigan, 1985.

Thesis (doctoral)--University of Göteborg, 1979, and five supporting articles. / "Translation and revision of English text by John Gulliver." At head of title: Dept. of Orthodontics, Faculty of Odontology, University of Göteborg, Sweden. Includes bibliographical references.

Thesis (doctoral)--University of Göteborg, 1979, and five supporting articles. / "Translation and revision of English text by John Gulliver." At head of title: Dept. of Orthodontics, Faculty of Odontology, University of Göteborg, Sweden. Includes bibliographical references.

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