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Patterns of fusimotor innervation by γ-efferents in cat peroneus tertius (1983)

Petit, J. ; Cameron, W. E. ; Murthy, K. S. K. ; [et al.]

Springer

Experimental brain research 51 (1983), S. 146-152

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ISSN: 1432-1106

Keywords: Muscle spindles ; γ-Efferents ; Fusmotor innervation

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Summary The pattern of γ-efferent innervation of the muscle spindle was investigated in the peroneus tertius muscle of the cat. A number of spindle group Ia afferents were isolated and monitored during tetanic stimulation of isolated γ-axons. The sample was dominated by efferents producing a static fusimotor effect on the afferent. An individual static axon normally projected to less than five but at times as many as seven muscle spindles. Each spindle normally received innervation from three to five static γ-efferents but occasionally up to eight. The number of spindles innervated by a static γ-axon was directly related to the efferent axonal conduction velocity. For each experiment, a probability distribution of the number of fusimotor effects was constructed from all available connections between the muscle spindles and static γ-efferents considered in matrices of four afferents and four efferents. This distribution was then compared to a random binomial distribution. In each of the ten experiments, statistically significant differences (p〈0.01) were noted between the experimental and random distributions. In order to interpret such deviations from the random distributions, similar analyses were performed on various combinations of afferents and efferents in simulated sets displaying grouping of effects. It was concluded that the observed differences between experimental and random distributions may be produced by a grouping of fusimotor innervation limited to a small set of spindles.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00236812

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Ankle flexor muscles in the cat: Length-active tension and muscle unit properties as related to locomotionSupported in part by the Institutional Studies and Research Committee of Northern Arizona University and by USPHS Grant Ns 07888 to D. G. Stuart. (1977)

Goslow, G. E. ; Cameron, W. E. ; Stuart, D. G.

New York, NY : Wiley-Blackwell

Journal of Morphology 153 (1977), S. 23-37

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ISSN: 0362-2525

Keywords: Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Medicine

Notes: The mechanical properties of the whole muscle and fast-twitch muscle units of the cat hindlimb pretibial flexors have been explored and related to normal locomotion. Tibialis anterior (TA) is parallel-fibered and functionally crosses a single joint, the ankle, whereas extensor digitorum longus (EDL) is pinnate and spans the ankle, knee, metatarsophalangeal and interphalangeal joints. The active tetanic tension of TA remains near its peak value over a range of muscle lengths associated with normal ankle movement. In contrast, the length-tension curve of EDL is sharply peaked. However, normal corollary action of the knee, ankle and metatarsophalangeal joints during stepping minimizes EDL's excursion and maintains it at or near a length optimal for peak tension development. EDL is capable of producing synchronous but sterotyped digit and ankle movements while TA provides for independent ankle flexion at all relevant joint angles.The mechanical properties of 84 TA and 98 EDL fast-twitch muscle units were studied by measuring twitch contraction time (≤45 msec), peak tetanic tension, response to repetitive stimulation, and contractile fatigue resistance during electrical stimulation of single alpha axons, functionally isolated from ventral root filaments. These mechanical properties were essentially similar for both muscles with the exception of mean peak tetanic tension which was 30% lower for TA units (14 gm-wt) than for EDL units (20 gm-wt). A high proportion of units in both muscles demonstrated fatigue resistance which is reflective of the repetitive, phasic demand upon these muscles during locomotion.

Additional Material: 7 Ill.