Physiological identification of static ? axons in primate muscle

Abstract

Skeletofusimotor (beta) axons exerting a static action on spindle primary endings were identified in the peroneus brevis and tertius muscles of the cynomolgus monkey. In most of the identified static beta motor units, the extrafusal portion was of the fast-contracting fatiguable type.

The mammalian muscle spindle and its central control

“…3-Innervation has now been found in a number of different muscles and species (cat, monkey, rat, rabbit, man;Cooper and Daniel 1963;Bessou et al 1963Bessou et al , 1965Adal and Barker 1965;Emonet-D~nand et al 1966Emonet-D~nand et al , 1970Emonet-D~nand et al , 1975Swash and Fox 1972;Andrew and Part 1974;Barker 1974a;Emonet-D~nand and Laporte 1975;Mc William 1975;Laporte and Emonet-DOnand 1976;Cheney and Preston 1976b;Harker et al 1977;Murthy et al 1982;Murthy 1983).…”

“…Frequently these axons innervate skeletal muscle fibres of the fast, oxidative-glycolytic type. In contrast, the slower 3-axons (below 85 m/s), which mostly supply muscle fibres of the slow oxidative type, exert dynamic action (Barker et al 1977;Harker et al 1977;Laporte 1979;Emonet-D~nand et al 1980a;Jami et al 1982;Murthy 1983).…”

Human Muscle Spindle Sensitivity Reflects the Balance of Activity between Antagonistic Muscles

“…Reciprocal inhibition of fusimotor drive has been demonstrated previously for ␥ motor neurons of intercostal muscles in the cat (Sears, 1964). Because the purpose of reciprocal inhibition is to prevent or otherwise curb contractile force production in the antagonist muscle, ␤ motor neurons may also be reciprocally inhibited, because a proportion of these neurons in cat (Jami et al, 1982) and the overwhelming majority of these neurons in the primate (Murthy, 1983) innervate motor units of the fast-twitch fatigable type, capable of producing high forces.…”