Stretch-sensitive mechanoreceptors in the frog sartorius muscle.
The sartorius muscle of the frog Litoria aurea contains two populations of mechanoreceptors. Commonest are the muscle spindles served by afferent fibres conducting at 24-42 m/sec. Each muscles also contains two or three high threshold receptors identified as extrafusal receptors with afferents conducting at 14-22 m/sec. Extrafusal receptors unlike spindles did not show a resting discharge even in the presence of high levels of resting tension in the muscle. Furthermore their responses to both stretch and contraction were weak and variable. It is concluded that extrafusal receptors should not be compared with muscle spindles or tendon organs but with the high threshold pressure and nociceptors known to occur in mammalian muscle.
Birchall
R L
RL
Department of Physiology, Monash University, Clayton, Victoria 3168, Australia.
Proske
U
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