Discharges of Tendon Organs During Unfused Muscle Contractions
The mechanoreceptor complement of mammalian skeletal muascle includes Golgi tendon organs, which are innervated by Ib afferent fibres and considered as contraction sensors because their sensitivity for this stimulus is very high (Houk and Henneman, 1967). The typical location of a tendon organ is at the myotendinous junction. Within the capsule of a tendon organ, sensory endings contact collagen bundles connected at one end with a small fascicle of muscle fibres (in-series muscle fibres), while the other end is in continuity with either tendon or aponeurosis. Several motor units contribute fibres to the fascicle and the tendon organ can signal the contraction of each unit because the twitch of a single in-series muscle fibre, pulling on the receptor, is enough to elicit a discharge (Fukami, 1981). Each tendon organ thus monitors the activity of a small set of 10–15 motor units, belonging to different physiological types (Reinking et al., 1975). Since, in addition, each of these units usually activates several tendon organs, a comparison of the numbers of motor units and of tendon organs in cat leg muscles suggests that the contraction of every single motor unit in these muscles is monitored by at least one tendon organ (Jami and Petit, 1976a).
KeywordsMotor Unit Contractile Force Discharge Frequency Single Motor Unit Myotendinous Junction
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