Development of the sensory innervation of muscle spindles in the kitten

Patak, A.; Proske, Uwe; Turner, Helen R; Gregory, John E

doi:10.1016/0736-5748(92)90009-o

Cited by 6 publications

(1 citation statement)

References 17 publications

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“…The bag 1 and earliest chain fibres followed during days 38–41; and both the first recognizable secondary ending and the first tandem‐linked, small capsule ( b 2 c unit) were found during days 41–43. Chain fibres continue to be generated until about the time of birth, and possibly secondary endings also, as Patak et al. (1992) reported that spindles from hind‐limb muscles of new‐born kittens mostly possessed only primary endings, whereas from 1 week post natal the commonest sensory complement was PS.…”

Section: Discussionmentioning

confidence: 99%

A comparative analysis of the encapsulated end‐organs of mammalian skeletal muscles and of their sensory nerve endings

et al. 2009

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SummaryThe encapsulated sensory endings of mammalian skeletal muscles are all mechanoreceptors. At the most basic functional level they serve as length sensors (muscle spindle primary and secondary endings), tension sensors (tendon organs), and pressure or vibration sensors (lamellated corpuscles). At a higher functional level, the differing roles of individual muscles in, for example, postural adjustment and locomotion might be expected to be reflected in characteristic complements of the various end-organs, their sensory endings and afferent nerve fibres. This has previously been demonstrated with regard to the number of muscle-spindle capsules; however, information on the other types of end-organ, as well as the complements of primary and secondary endings of the spindles themselves, is sporadic and inconclusive regarding their comparative provision in different muscles. Our general conclusion that muscle-specific variability in the provision of encapsulated sensory endings does exist demonstrates the necessity for the acquisition of more data of this type if we are to understand the underlying adaptive relationships between motor control and the structure and function of skeletal muscle. The present quantitative and comparative analysis of encapsulated muscle afferents is based on teased, silver-impregnated preparations. We begin with a statistical analysis of the number and distribution of muscle-spindle afferents in hind-limb muscles of the cat, particularly tenuissimus. We show that: (i) taking account of the necessity for at least one primary ending to be present, muscles differ significantly in the mean number of additional afferents per spindle capsule; (ii) the frequency of occurrence of spindles with different sensory complements is consistent with a stochastic, rather than deterministic, developmental process; and (iii) notwithstanding the previous finding, there is a differential distribution of spindles intramuscularly such that the more complex ones tend to be located closer to the main divisions of the nerve. Next, based on a sample of tendon organs from several hind-foot muscles of the cat, we demonstrate the existence in at least a large proportion of tendon organs of a structural substrate to account for multiple spike-initiation sites and pacemaker switching, namely the distribution of sensory terminals supplied by the different first-order branches of the Ib afferent to separate, parallel, tendinous compartments of individual tendon organs. We then show that the numbers of spindles, tendon organs and paciniform corpuscles vary independently in a sample of (mainly) hind-foot muscles of the cat. Grouping muscles by anatomical region in the cat indicated the existence of a gradual proximo-distal decline in the overall average size of the afferent complement of muscle spindles from axial through hind limb to intrinsic foot muscles, but with considerable muscle-specific variability. Finally, we present some comparative data on muscle-spindle afferent complements of rat, rabbit and guinea pig, on...

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Section: Discussionmentioning

confidence: 99%

A comparative analysis of the encapsulated end‐organs of mammalian skeletal muscles and of their sensory nerve endings

et al. 2009

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Structural and functional maturation of the buccal stretch receptors in rats

et al. 1996

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Postnatal functional and structural development of the buccal stretch receptor (BSR) of rats was investigated, using electrophysiological and morphological techniques. For functional analysis, sustained discharges in response to ramp-and-hold stretches were recorded from the BSRs isolated from animals aged 10 days to 10 weeks. The threshold amplitude of stretch for a sustained discharge fell significantly between 10 days and 3 weeks, reaching adult values at 5 weeks of age, while the static sensitivity increased conspicuously between 2 and 4 weeks after birth. On the other hand, between 1 and 4 weeks of age, apparent structural changes in the BSR were observed on the number of preterminal branches in a sensory unit, the size of the varicose-like swellings along the terminal axon, the density of collagen and elastic fibers around the core structure, and the content of the sub-capsular space. From these results, we suggest that the increase in the density of the connective tissue around the core structure is associated with an enhancement in the elasticity of the BSR in the early postnatal stages, decreasing the threshold amplitude of stretch for a sustained discharge. One possible explanation for the maturation of the static sensitivity of this receptor is growth of the sensory axon terminals filled with dense mitochondria.

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