Identification of intrafusal muscle fibres activated by single fusimotor axons and injected with fluorescent dye in cat tenuissimus spindles.

Abstract

3. In one spindle Procion Yellow was injected into two intrafusal muscle fibres activated by the same static y axon; they were identified as a bag2 and a chain fibre.4. Nine intrafusal muscle fibres innervated by dynamic y axons were identified as seven bag, fibres, one bag2 fibre, and one long chain fibre.5. In one spindle two bag fibres were injected, one activated by a dynamic y axon, the other by a static y axon; the former proved to be a bag1 fibre, the latter a bag, fibre.6. Stimulation of static y axons elicited junctional potentials in seven bag2 fibres and one damaged chain fibre, and action potentials in one bag2 and four chain fibres. In the whole sample of impaled intrafusal muscle fibres (identified and unidentified) activated by static axons, junctional potentials were recorded from twenty-three (62.2 %), and action potentials from fourteen (37v8 %). Stimulation of dynamic y axons always elicited junctional potentials.7. In a number of instances it was possible to examine the ultrastructure of motor endings belonging to the stimulated y axon. The myoneural junctions of trail endings supplied by static y axons to bag2 and chain fibres were both smooth and folded; the deepest and most regular folding occurred on chain fibres. The terminals of P2 plates supplied to bag1 fibres by dynamic y axons had smooth myoneural junctions.

The mammalian muscle spindle and its central control

“…Reports based on four different techniques all agreed that static 7-fibres innervated both bag and chain fibres non-selectively, whereas dynamic axons were specific for bag fibres (see Laporte and Ernonet-Dbnand 1973). The techniques used were: first, chronic denervation experiments sparing only a single static 7-fibre ( Barker et al 1973); second, the first application by Brown and Butler (1973,1975) of the glycogen-depletion technique (Edstr6m and Kugelberg 1968) to mark the intrafusal muscle fibres, operated by identified 7-axons; third, the visual observation (in isolated spindles) of intrafusal movements provoked by individual 7-fibres (Bessou and Pages 1975); and fourth, the investigation of the intrafusat targets of single 7-axons using intracellular recording from muscle fibres and subsequent histological identification (Barker et al 1972(Barker et al , 1978.…”

Identification of Muscle Spindles in the Submentalis Muscle of the Marine Toad, Bufo marinus and Its Potential Proprioceptive Capacity in Jaw–Tongue Coordination

“…The ultrastructure of these organs are well described in birds and mammals, but poorly known from amphibians (Barker et al, 1978;Ruskell, 1990;Patten and Ovalle, 1991). The goal of this study was, therefore, to investigate the presence of muscle spindles in the submentalis muscle of the marine toads.…”

Analysis of Motor Fibers in the Communicating Branch between the Cervical Nerves and the Spinal Accessory Nerve to Innervate Trapezius in the Rat

“…The g motor fibers distribute on the polar portions of both bag and chain fibers (Barker et al, 1978;Kucera, 1980;Banks, 1991;Maier, 1992Maier, , 1997; Emonet-Dé nand et al, 1998, 2001). Our findings that the motor elements from the communicating branch were distributed on the polar regions of the intrafusal fibers (both bag and chain fiber) definitively.…”