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

Abstract

S U M M A R YMuscle spindle density is extremely high in the deep muscles of the human neck. However, there is a paucity of information regarding the morphology and immunoreactivity of these muscle spindles. The objective of this study was to investigate the intrafusal fiber content and to assess the myosin heavy chain (MyHC) composition of muscle spindles from human deep neck muscles. In addition to the conventional spindles containing bag 1 , bag 2 , and chain fibers (b 1 b 2 c spindle), we observed a number of spindles lacking bag 1 (b 2 c spindle) or bag 2 (b 1 c spindle) fibers. Both bag 1 and bag 2 fibers contained slow tonic MyHCs along their entire fiber length and MyHCI, MyHCIIa, embryonic, and ␣ -cardiac MyHC isoforms along a variable length of the fibers. Fetal MyHC was present in bag 2 fibers but not in bag 1 fibers. Nuclear chain fibers contained MyHCIIa, embryonic, and fetal isoforms with regional variations. We also compared the present data with our previous results obtained from muscle spindles in human biceps brachii and the first lumbrical muscles. The allotment of numbers of intrafusal fibers and the MyHC composition showed some muscle-related differences, suggesting functional specialization in the control of movement among different human muscles.

Aberrant expression of myosin isoforms in skeletal muscles from mice lacking therev-erbAαorphan receptor gene

“…However, it is interesting to note the similar ␤-galactosidase staining pattern in intrafusal and extrafusal muscle fibers, i.e., a stronger staining intensity in homozygous than in heterozygous animals. Intrafusal muscle fibers express MyHC isoforms that are not expressed in extrafusal limb muscles (30,31,41), and this may explain the weaker ␤-galactosidase staining intensity in intrafusal than in extrafusal muscle fibers.…”

Neck muscle vibration can improve sensorimotor function in patients with neck pain

“…(i) A unique feature of the cervical spine is the high density of muscle spindles [29,30]. Vibration to the muscles alters afferent discharge of muscle spindles [31], which in turn can affect the body perception [32].…”

The Effect of Cervical Spine Manipulation on Postural Sway in Patients With Nonspecific Neck Pain

“…This is especially true of the suboccipital musculature which possess around 200 spindles/g of muscle (Boyd-Clark, Briggs, & Galea, 2002;Kulkarni, Babu, & Chandy, 2001). By comparison, the first lumbrical in the thumb contains a mere 16 spindles/g of muscle, and the gluteus maximus contains a mere 0.8 spindles/g (Liu, Thornell, & Pedrosa-Domellöf, 2003;Treleaven, 2008a). The proprioceptive capability of the cervical spine is drawn upon by numerous supraspinal and reflex mechanisms.…”

“…Anatomical and physiological studies of the cervical spine suggest that the upper cervical region may make a greater contribution to the postural control system than lower levels. In particular, it has been noted that the numerous connections that exist between cervical afferents and the vestibular, visual and reflex subsystems that contribute to head and eye orientation as well as postural control, arise predominantly from the upper cervical region (Barmack, 2003;Dubrovsky & Barbas, 1977;Liu et al, 2003;Morningstar et al, 2005;Rose, Wainwright, & Neuber-Hess, 1992;Shinoda, Ohgaki, Sugiuchi, & Futami, 1989). In addition, it has been found that the muscles of the suboccipital region possess far greater numbers of proprioceptive muscle spindles than the deep musculature of the lower cervical spine.…”