| Popis: |
It is clear from even a cursory examination of the literature on muscle spindles that these are receptors of great sophistication and functional versatility. But a simple textbook ‘role’ for them in the serious business of motor control cannot be formulated realistically without taking into account that some information they signal is inconsequential to motor control, as for example when spindle afferents are influenced by the arterial pulse (Ellaway & Furness, 1977), and γ-motoneurones are influenced by laughing and mental arithmetic (Ribot, Roll & Vedel, 1986). Clearly their involvement is detachable, which presumes there are rules for engaging and disengaging them. Their participation is context specific; information from spindles must not only be interpreted in the context of any current motor act, but also be set against the gamut of information continually flowing into the spinal cord from other receptors — joint, cutaneous and all. The high stretch sensitivity of primary sensory endings sometimes must be essential to motor control, and at other times irrelevant and even dangerous, and will need to be excluded. This is not new (e.g. Graham Brown, 1911; Forssberg, Grillner & Rossignol, 1975; Taylor & Gottlieb, 1985). |
