Như đã thảo luận trước đó trong chương này, MIFs được kết hợp với kết thúc rào lại lời khuyên của họ trong các đường giao nhau myotendinous. Kể từ khi kết thúc rào lại các thụ thể cảm giác giả định, sự kết hợp MIF-rào lại đã được so sánh với một cơ quan gân Golgi chưa trưởng thành | ically firing units 12 62 63 . It is not clear how much they contribute to the tension of eye muscles in natural conditions but experimentally exposing eye muscle to succinyl choline which causes the contraction of MIFs alone causes tension changes and indicates that MIF could contribute to tension in the eye muscle 64 . As discussed earlier in this chapter MIFs are coupled with palisade endings at their tips in the myotendinous junction. Since palisade endings are putative sensory receptors the MIF-palisade combination has been compared to an immature Golgi tendon organ 45 or an inverted muscle spindle where the MIF represents an overgrown nuclear bag fiber and the palisade ending its displaced primary sensory endings 65 . It is possible that this structure could provide a sensory or proprioceptive feedback signal to the central nervous system and its afferent signal would be modulated by the activity of the MIF motoneurons. It is still too early to decide what role MIF motoneurons play in the control of eye movements but currently evidence supports the idea that the SIF or twitch motoneurons primarily drive the eye movements whereas the MIF or nontwitch or tonic motoneurons participate in determining tonic muscle activity as in eye alignment vergence and gaze holding. Conclusions Current evidence supports the concept that MIF motoneurons carry a tonic eye position signal and the SIF or twitch motoneurons an additional phasic signal driving the actual eye movements. The role of MIFs and palisade endings is still speculation. However they are constant features of human eye muscles and they draw attention to the myotendinous junction. In the light of the MIF-palisade proprioceptive hypothesis it is possible that the myotendinous junction is a site from which sensory signals can be sent to the central nervous system and in turn influence muscle tension and perhaps eye alignment. This hypothesis should be considered seriously in the plans for the surgical operations .
