Premium
The response to stretch of human intercostal muscle spindles studied in vitro.
Author(s) -
Davis J N
Publication year - 1975
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.1975.sp011030
Subject(s) - intercostal muscle , anatomy , chemistry , in vivo , intercostal space , biophysics , biology , respiratory system , microbiology and biotechnology
1. The discharge properties of human muscle spindles have been studied in vitro in a preparation based on the biopsied external intercostal muscle. 2. The static and dynamic responsiveness of thirty‐six endings in twenty visualized and histologically identified spindles have been investigated using amplitudes and velocities of stretch likely to encompass those occurring in vivo. 3. The dynamic index, measured at a stretch velocity of 3 mm/sec, ranged from 3 to 40 impulses/sec and was distributed bimodally, consitent with the presence of primary and secondary endings. 4. The relationship between the dynamic index and the velocity of stretch was approximately linear both for primary and secondary endings up to the maximum velocity tested (10 mm/sec). 5. The frequency/extension relationship was approximately linear for both primary and secondary endings. The mean values of the slope for primary and secondary endings were 16–1 +/− 8–3 S.D. of the observation and 12–1 +/− 6–5 impulses/sec per five per cent extension. 6. The slopes of the frequency/extension relationship for endings lying in the same spindle were positively correlated, significant at the 10% level. 7. It was estimated from the results in vitro that the position sensitivity of human intercostal spindles in vivo ranges from 2 to 21 impulses/sec per millimetre.