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EXPERIMENTAL PRODUCTION OF GRADED MUSCULAR CONTRACTIONS OF NATURAL FORM IN THE DIAPHRAGM AND IN SKELETAL MUSCLE
Author(s) -
Briscoe Grace
Publication year - 1928
Publication title -
quarterly journal of experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0370-2901
DOI - 10.1113/expphysiol.1928.sp000450
Subject(s) - contraction (grammar) , muscle contraction , diaphragm (acoustics) , phrenic nerve , respiration , skeletal muscle , stimulation , anatomy , diaphragm muscle , chemistry , respiratory system , physics , medicine , vibration , acoustics
1. Graded muscular contractions of natural form can be obtained by a new method of electrical stimulation described. 2. Applied to the cut end of one phrenic, the resultant contraction and relaxation of the paralysed half of the diaphragm can be varied so as to reproduce almost exactly the natural movements of the sound half of the muscle. 3. This variation in contraction and relaxation is obtained by imparting to the secondary coil of an induction apparatus varying degrees of to‐and‐fro movement differing in rhythm, in extent of movement, and in rates of approach and withdrawal. 4. In natural respiration the diaphragm is always in a state of postural contraction during the expiratory pause. The appropriate degree of postural tonus can be maintained in experimental muscle by allowing minimal currents to pass into the nerve between the phasic contractions. 5. The pattern of stimuli (a periodic variation of amplitude imposed upon a basic frequency of interruption at a fast rate) sent into the nerve during imitation of normal respiration resembles the pattern of action‐currents picked up from the phrenic during natural respiration, and also resembles the action‐currents of muscles in voluntary contraction. 6. The method can be applied to the skeletal nerve‐muscle preparation, and graded contractions of any form can be obtained from it. It is suggested that the type of stimulation employed is an example of “asynchronous multi‐fibre summation.” I am grateful to Miss W. Leyshon , Ph. D., for the assistance and advice she has given me on the physical side of this work. I have also to acknowledge much assistance on the experimental side from Mr William Lofts . My thanks are due to Professor Cullis and to the Council of the School for a grant from the Waller Memorial Research Fund, and for the hospitality of their laboratories.