Somatotopic relations between the motor nucleus and its innervated muscle fibers in the cat tibialis anterior

Iliya, Afif; Dum, Richard P.

doi:10.1016/0014-4886(84)90186-9

Cited by 120 publications

(19 citation statements)

References 35 publications

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“…Fibres on the K side of the 1250 fibre region would be expected to be innervated by more K than F axons, and, similarly, fibres on the F side of the region would be expected to be innervated by more F than K axons; random synapse elimination would be expected to produce less intermixture at the extremes of this 1250 fibre region. We conclude that there is no This conclusion is in general agreement with findings reported by Iliya & Dum (1984), Donahue & English (1985) and English (1986). Jliya and Dum demonstrated compartments in the tibialis anterior muscle of 6-week-old kittens, near the end of synapse elimination.…”

Section: Discussionsupporting

confidence: 82%

“…Recently, however, it has been used almost exclusively to describe a group of muscle fibres which occupy a contiguous, reproducible region of a muscle and which are innervated by a branch of a muscle nerve. Using this definition, the compartmental pattern of innervation is relatively common in skeletal musculature Galvas & Gonyea, 1980;Bodine et al 1982;Iliya & Dum, 1984;Richmond et al 1985). The rat EDL can be added to the list of muscles having this pattern of motor innervation.…”

Section: Discussionmentioning

confidence: 99%

“…The compartmentalized pattern of innervation in some muscles has been suggested to be related to a segmentotopic projection from the spinal cord to the muscle Iliya & Dum, 1984;Richmond, MacGillis & Scott, 1985;Weeks & English, 1985). The segmentotopy of the EDL innervation and its relation to the two compartments was examined by determining the projections of anteriorly located (derived from the L4 ventral root) and posteriorly located (derived from L5) motoneurones to the K and F compartments.…”

Section: Fibre Type Composition Of Muscle Compartmentsmentioning

confidence: 99%

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The organization and development of compartmentalized innervation in rat extensor digitorum longus muscle.

Balice-Gordon

Thompson

1988

The Journal of Physiology

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SUMMARY1. We have examined the innervation of the rat extensor digitorum longus (EDL) muscle by the two extramuscular branches formed from the bifurcation of its muscle nerve. Observations of muscle contractions, recordings of end-plate potentials, and glycogen depletion of young adult muscles show that each branch innervates a separate region or 'compartment' in the muscle. The branch entering the muscle nearer the knee (the K branch) innervates fibres in the anteromedial half of the muscle whereas the branch entering closer to the foot (the F branch) innervates fibres located posterolaterally. Individual EDL motoneurones project either into the K or the F branch and therefore innervate fibres located in one compartment. The boundary between the compartments is usually sharply delineated. No obvious anatomical feature exists within the muscle which would explain the division of the muscle into two distinct regions.2. The presence of a segmentotopic projection from the spinal cord to the muscle was investigated to evaluate its possible contribution to the compartmental pattern. The most posterior neurones of the EDL motor pool were found to project more frequently to the posterolateral F compartment; similarly, the most anterior neurones most frequently project to the anteromedial K compartment. However, each compartment is innervated by both anteriorly and posteriorly located motoneurones. The segmentotopic projection is too weak to explain the presence of neuromuscular compartments.3. The post-natal period of synapse elimination appears to play at best a minor role in setting up the compartmentalized innervation. Glycogen depletion and intracellular recording in 1-2-day-old muscles show that each nerve branch innervates fibres in the same region of the muscle as in the adult. Most of the fibres in each compartment are polyneuronally innervated by axons in their own particular nerve branch, although fibres located near the boundary between the two compartments are innervated by axons from both nerve branches. This convergent innervation from the two branches disappears in concert with the elimination of * Present address:

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Section: Discussionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: Fibre Type Composition Of Muscle Compartmentsmentioning

confidence: 99%

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The organization and development of compartmentalized innervation in rat extensor digitorum longus muscle.

Balice-Gordon

Thompson

1988

The Journal of Physiology

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“…However, in other muscles, including the external intercostals, jawclosing and ankle extensors, in which tonic and phasic patterns of y discharge have also been described during rhythmic movements, a direct, though not necessarily the same, correspondence with static and dynamic types has been proposed in each case (Appenteng et al 1980;Murphy et al 1984;Greer & Stein, 1990). The simplest interpretation of the present results is a direct equivalence and this seems particularly appropriate in view of the relatively simple action of the muscle involved (ankle flexor), and since y-efferents were recorded from a nerve branch (anterior) which supplies, almost exclusively, one of the two intramuscular compartments of TA (Iliya & Dum, 1984). Notwithstanding these comments, we have already discussed the unlikelihood of a significant numnber of phasic units being dynamic in nature.…”

Section: P R Murphy and G R Haimond Discussionsupporting

confidence: 71%

“…Functionally single y-motoneurones were recorded from the anterior branch (Iliya & Dum, 1984) of the cut TA nerve on twin platinum wire electrodes. A silastic cuff containing two stimulating 60 y-MOTONEURONE DISCHARGE DURING LOCOMOTION electrodes was placed around the common peroneal nerve.…”

Section: Recordings and Stimulationmentioning

confidence: 99%

The locomotor discharge characteristics of ankle flexor gamma‐motoneurones in the decerebrate cat.

Murphy

Hammond

1993

The Journal of Physiology

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SUMMARY1. The discharge patterns of ankle flex.or, tibialis anterior (TA), y-motoneurones were recorded during locomotion in the decerebrate cat.2. At rest y-efferents had no background discharge. During locomotion two patterns of y activity could be distinguished. Most units (16) were phasically recruited with homonymous electroneurogram (ENG) activity, while the remainder (5) were tonically active throughout the step cycle.3. The modulation of phasic units was greater (P < 001) than tonic neurones. Phasic units had lower (P < 0-02) mean, but higher (P < 0-01) peak, rates during the step cycle.4. The discharge rate of both types of efferent increased around the onset of ENG activity and peaked during ENG activity, or shortly after its cessation. The conduction velocities of phasic and tonic units overlapped widely.5. It is proposed, on the basis of muscle spindle afferent recordings during locomotion, that TA phasic and tonic units correspond to static and dynamic ymotoneurones, respectively. This correspondence is functionally advantageous for the role of ankle flexor muscles during locomotion. Thus phasic static y discharge during flexion would aid muscle contraction via increased I a afferent activity, while tonic dynamic y firing would enhance I a afferent stretch sensitivity throughout the step cycle. Such enhancement during flexion would oppose unexpected muscle lengthening while, during extension, it would contribute to reciprocal inhibition of ankle extensor muscles.6. The results are discussed in relation to strategies of y usage during rhythmic movements. It is postulated that, for such behaviour, muscle contraction is accompanied by coactivity in static and dynamic y-motoneurones. A functional rationale is suggested for this strategy.

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Functional somatotopic organisation of motoneurons supplying the rabbit masseter muscle

Weijs

1996

J. Comp. Neurol.

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The localisation within the trigeminal motor nucleus of motoneurons supplying different regions of the rabbit masseter muscle was investigated to test the hypothesis that muscle regions with different motor tasks are controlled from different subregions of the motor nucleus. Motoneurons were labeled retrogradely with horseradish peroxidase, applied surgically to small sections of the masseter in 22 animals, and also by applying this tracer to the cut masseteric nerve. After sacrifice, the labeled muscle sections were mapped. The distribution of labeled motoneurons within the nucleus was described and compared for the muscle regions. The motoneurons for the masseter muscle are confined to the dorsal and lateral sections of the motor nucleus, along its full rostrocaudal extent. Within this subnucleus, the motoneurons for the superficial masseter occupy the dorsolateral portion, the motoneurons for the deep masseter the dorsomedial portion. The anatomical and functional subdivision of the deep masseter into an anterior and posterior portion appeared to be matched by a separation of the motoneurons for these portions in the rostrocaudal direction along the nucleus. The separation of the motoneurons for the anterior and posterior deep masseter is not complete; the territories in the motor nucleus overlap each other for about 50%. The well-established differentiation in motor tasks between the masseter portions during feeding is thus clearly reflected in a separation of motoneurons, making possible differentiation of descending or afferent input to the separate regions in the nucleus.

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Somatotopic relations between the motor nucleus and its innervated muscle fibers in the cat tibialis anterior

Cited by 120 publications

References 35 publications

The organization and development of compartmentalized innervation in rat extensor digitorum longus muscle.

The organization and development of compartmentalized innervation in rat extensor digitorum longus muscle.

The locomotor discharge characteristics of ankle flexor gamma‐motoneurones in the decerebrate cat.

Functional somatotopic organisation of motoneurons supplying the rabbit masseter muscle

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