Morphology and distribution of muscle spindles in dorsal muscles of the cat neck

Abstract

Silver-stained sections have been examined from the five dorsal neck muscles splenius, biventer, cervicis, complexus, rectus capitis major, and occipitoscapularis. Every serial section was examined for at least one muscle of each type so that a complete description of the spindle distribution and morphology could be made. With the exception of occipitoscapularis (whose prime function is probably in scapula rotation and not in head movement), neck muscles have a remarkably high spindle density. Occipitoscapularis has a spindle density similar to that of hindleg locomotor muscles (13-19 per gram), but splenius has a density of 46-66 per gram, biventer cervicis 74-96 per gram, complexus 71-107 per gram, and rectus capitis major 48-84 per gram. Such high densities have only previously been seen in small muscles whose total spindle population is not large. Because of the relatively large size of some neck muscles, individual muscles with a spindle content of up to 254 spindles have been found.

Muscle Spindles in the Deep Muscles of the Human Neck: A Morphological and Immunocytochemical Study

“…The linked forms observed in the present study generally fitted the previous descriptions of parallel and paired muscle spindles in cat neck muscles (Richmond and Abrahams 1975;Richmond 1981,1982). The latter was the most commonly found in the present study.…”

“…One-bag-fiber spindles have been described in the cat (Banks et al 1979;Kucera 1982;Kucera and Walro 1987), particularly in the neck muscles (Richmond and Abrahams 1975;Richmond 1981,1982;Richmond et al 1986;Abrahams and Richmond 1988). However, all the one-bag-fiber spindles in cat muscles selectively lack bag 1 fibers (with one reported exception; Kucera 1982), usually appear as part of spindle complexes (Richmond and Abrahams 1979;Richmond 1981,1982;Richmond et al 1986;Abrahams and Richmond 1988), and are restricted to the regions near tendons or tendinous inscriptions in dorsal neck muscles (Bakker and Richmond 1981).…”

The Neurochemically Diverse Intermedius Nucleus of the Medulla as a Source of Excitatory and Inhibitory Synaptic Input to the Nucleus Tractus Solitarii

“…Furthermore, the stimulus intensities used were consistent with those that would activate muscle spindle and Golgi tendon organ afferents. Because this cervico-sympathetic reflex appears to originate from muscle spindles in the dorsal neck musculature, it is very likely that the suboccipital muscle group is involved in the reflex because these muscles have an extremely high muscle spindle content (Richmond and Abrahams, 1975;Kulkarni et al, 2001). Additional evidence for the involvement of the suboccipital muscle group in the cervico-sympathetic reflex comes from changes in blood pressure associated with chiroprac- tic manipulations of the C1 vertebrae (McKnight and DeBoer, 1988;Knutson, 2001), which would result in altering the length of fibers in the suboccipital muscle group.…”

Frontal projections of dorsal neck and extraocular muscles

“…The dorsal neck muscles constitute an anatomically and functionally complex group of muscles (23,46,47). Postural reflex responses of neck origin have been clearly established (48) and reflex responses of neck origin in extraocular muscles have been well known since their first obser-vation by Barany in 1907 (11).…”

“…The high density of receptors in both extraocular (3,27) and dorsal neck muscles (27,47), the currently recognized role of muscle receptors in kinesthesia (26), and the fact that muscle information can be utilized to control the activity of regard (34), suggest a role of these afferents in the control of sequentially organized coordinated eyehead movement.…”