Patterns of fusimotor innervation by ?-efferents in cat peroneus tertius

1983 ◽  
Vol 51 (1) ◽  
Author(s):  
J. Petit ◽  
W.E. Cameron ◽  
K.S.K. Murthy ◽  
L.A. Barone
Keyword(s):  
Fusimotor Innervation

The Early Development of Muscle Spindles in the Rat

1973 ◽  
Vol 12 (1) ◽  
pp. 175-195
Author(s):  
ALICE MILBURN
Keyword(s):  
Close Association ◽  
Large Diameter ◽  
Muscle Spindles ◽  
Muscle Fibres ◽  
Intrafusal Muscle ◽  
Intrafusal Fibres ◽  
Fusimotor Innervation ◽  
Nuclear Chain ◽  
Intramuscular Nerve

The morphogenesis of muscle spindles in rat lower hind-limb muscles has been investigated using the electron microscope. The earliest detectable spindles are seen in the 19.5-day foetus and consist of a single myotube bearing simple nerve terminals of the large primary afferent axon from nearby unmyelinated intramuscular nerve trunks. The capsule forms by an extension of the perineural epithelium of the supplying nerve fasciculus, and is confined initially to the innervated zone. Myonuclei accumulate in this region, so that the first intrafusal muscle fibre to develop is a nuclear-bag fibre. Myoblasts, present within the capsule of the spindle throughout its development, fuse to form a smaller less-differentiated myotube by the 20-day foetal stage. This new myotube matures by close association with the initial fibre, and by birth (21-22 days gestation) has formed the smaller, intermediate bag fibre, that has been identified histochemically and ultrastructurally in the adult. The nuclear-chain fibres develop in the same way; myoblasts fuse to form satellite myotubes that mature in pseudopodial apposition to one of the other fibres within its basement membrane. This apposition consists of extensions of sarcoplasm from the developing myotube into the supporting fibre. By the 4-day postnatal stage the full adult complement of 4 intrafusal muscle fibres is present, although ultrastructural variations, seen in the adult, are not differentiated. The fusimotor innervation begins to arrive at birth, but is not mature until the 12th postnatal day, when the myofibrillar ultrastructural differentiation, including the loss of the M-line in the large-diameter bag fibre, is complete. The periaxial space appears at the same time. It is suggested that the sequential development of the intrafusal fibres is a reflexion of the decreasing morphogenetic effect of the afferent innervation, whereas the role of the fusimotor innervation is in ultrastructural, myofibrillar differentiation.

Possible fusimotor innervation to frog muscle spindles

1987 ◽  
Vol 415 (1) ◽  
pp. 144-148 ◽  
Author(s):  
M. Fujitsuka ◽  
M. Sokabe ◽  
A. Yoshimura ◽  
F. Ito
Keyword(s):  
Muscle Spindles ◽  
Frog Muscle ◽  
Fusimotor Innervation

Comparison of Static Fusimotor Innervation in Cat Peroneus Tertius and Longus Muscles

1998 ◽  
Vol 80 (1) ◽  
pp. 249-254 ◽  
Author(s):  
Françoise Emonet-Dénand ◽  
Yves Laporte ◽  
Julien Petit
Keyword(s):  
Statistical Analysis ◽  
Conduction Velocity ◽  
Muscle Fibers ◽  
Peroneus Longus ◽  
Intrafusal Muscle ◽  
Conduction Velocities ◽  
Intrafusal Muscle Fibers ◽  
Fusimotor Innervation ◽  
Motor Acts ◽  
Stimulation Of

Emonet-Dénand, Françoise, Yves Laporte, and Julien Petit. Comparison of static fusimotor innervation in cat peroneus tertius and longus muscles. J. Neurophysiol. 80: 249–254, 1998. Static fusimotor innervation was compared in cat peroneus longus and tertius muscles because the γ to spindle ratio is considerably higher in the longus (∼60 γ axons for 17 spindles) than in the tertius (∼24 γ axons for 14 spindles). Single γ axons were identified as static (γs) by their typical effects on the response of primary ending to ramp stretch. The intrafusal muscle fibers that single γs axons activated in the spindles they supplied were identified by the features of cross-correlograms between Ia impulses and stimuli, at 100 Hz, and by those of primary ending responses during stimulation at 30 Hz. In each experiment, a large proportion of the γ population was tested on about nine spindles. A statistical analysis was used to estimate the number of spindles supplied by single γs axons and the proportion of γs axons that supply only one spindle among those the stimulation of which had activated either bag2 or chain fibers alone in a single spindle. In peroneus longus, nearly all γs axons supply one or two spindles, whereas in peroneus tertius, the majority of γs axons supply from three to six spindles. The proportion of nonspecifically distributed γs axons, i.e., of axons that supply both bag2 fibers and chain fibers either in the same or in different spindles, is much lower (56%) in the longus than in the tertius (83%) as previously observed on a population of γs axons that supplied from three to six spindles. Correspondingly, the proportion of specific axons is much higher in the longus (44%) than in the tertius (17%). In none of the two muscles was a strict relationship observed between the conduction velocity of γs axons and their intrafusal distribution (specific bag2, specific chain fibers, nonspecific). However, γs supplying bag2 fibers either specifically or in combination with chain fibers tended to have faster conduction velocities, which suggests that, in various motor acts, the proportion of activated bag2 and chain fibers may be related to the proportions of activated fast and slow γs axons.

Prenatal Development of Muscle Spindles in the Mouse

1981 ◽  
Vol 39 ◽  
pp. 510-511
Author(s):  
Kenneth Kozeka
Keyword(s):  
Three Dimensional ◽  
Muscle Spindles ◽  
Prenatal Development ◽  
In Utero ◽  
Peripheral Region ◽  
Electron Microscopic ◽  
Afferent Nerves ◽  
Fusimotor Innervation ◽  
Spindle Development ◽  
Peripheral Regions

A closely spaced, serial, light and electron microscopic technique has permitted determination of the patterns of distribution, three dimensional cytoarchitecture and ultrastructural characteristics of developing muscle spindles in the fetal mouse extensor digitorum longus muscle (Figs. 1-6).Spindle development begins at 15 days in utero, when unmyelinated afferent nerves contact large, primary myotubes, located at the muscle's neurovascular hilum. By 17 days in utero the adult number of spindles containing one or two myotubes, can be identified in serial ultrathin sections through the myotube's sensory innervated region. While the primitive capsule of the spindle surrounds the intrafusal myotubes, it is initially confined to the sensory area and does not extend the length of the myotube. At this stage the peripheral regions of the intrafusal myotubes are morphologically indistinguishable from neighboring extrafusal myotubes.It is in this peripheral region that fusimotor innervation will develop.By following the spindles in serial, spaced (i.e., 15μm intervals), ultrathin transverse sections along their length, it is possible to establish the continuity of the sensory innervated region with the peripheral regions of the intrafusal myotube and to determine that fusimotor innervation is not present at 17 days in utero.

Development of fusimotor innervation correlates with group Ia afferents but is independent of neurotrophin-3

1998 ◽  
Vol 111 (2) ◽  
pp. 295-300 ◽  
Author(s):  
Thomas Ringstedt ◽  
Sjef Copray ◽  
Jon Walro ◽  
Jan Kucera
Keyword(s):  
Ia Afferents ◽  
Neurotrophin 3 ◽  
Fusimotor Innervation
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