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Response characteristics of muscle afferents in the domestic duck
Author(s) -
Dorward Patricia K.
Publication year - 1970
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1970.sp009262
Subject(s) - efferent , anatomy , tendon , muscle spindle , sciatic nerve , stimulation , stimulus (psychology) , afferent , chemistry , nerve conduction velocity , biology , neuroscience , psychology , psychotherapist
1. Response patterns of 116 muscle stretch receptor units isolated from the sciatic nerve of the duck have been studied, and the units classified as muscle spindles and tendon organs. 2. Units classified as spindles had low threshold tensions for maintained discharge. From conduction—velocity measurements, the calculated fibrediameter spectrum appears to be unimodal, ranging from 5 to 11–12 μm. 3. Spindle units showed essentially ‘in parallel’ behaviour, though increase in initial tension often led to the appearance of ‘in series’ responses. Although apparent ‘α‐excitation’ during maximal tetanic contractions was a common occurrence, no direct evidence of α‐innervation of spindles was obtained. 4. Evidence has been obtained for motor innervation of spindles by fibres distinct from those constituting the alpha supply to extrafusal muscle fibres. Afferent response attributable to this fusimotor innervation is influenced by initial tension and stimulus‐frequency. Electrical thresholds for fusimotor responses ranged from 1·1 to 4·03 times α maximum. 5. Tendon organ units consistently showed ‘in series’ response patterns during muscle contractions. They were not influenced by stimulation of the high‐threshold efferent nerve supply to the muscles. 6. Threshold tensions required for maintained discharge in tendon organ units from m. gastrocnemius pars lateralis were characteristically high; however, many units from m. flexor perforans et perforatus d. 3 had unexpectedly low mechanical thresholds. The calculated fibre‐diameter spectrum for tendon organ units is unimodal, ranging from 4–7 to 10–11 μm. As in mammals, they contribute to the coarse‐fibre component in the muscle nerve and include the fastest fibres present.