Heart-beat and pulse-wave / by C.S. Roy and J.G. Adami.

  • Roy, Charles S. (Charles Smart)
Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: Heart-beat and pulse-wave / by C.S. Roy and J.G. Adami. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

    12/88 (page 92)
    The third phase of the contraction of the musculi papillarcs is that of persistent contraction (d to d') unaccompanied by con- tinued shortening. This causes the curve to be more or less flattened at the top. At the point d' the relaxation of the papillary muscles begins, and this commencement of their relaxation precedes the begin- ning of the relaxation of the ventricular wall, as can be seen by a reference to Fig. 4, the letters on the two curves of which mark points which correspond in time. The contraction of the papil- lary muscle, therefore, not only begins later than that of the ventricular wall, but it comes to an end sooner. The period of contraction of the papillary muscles (from b to d) may be about half of that of the ventricle wall, although the difference in duration of the two is usually less than this, the relation being about 5 to 8; the relation at all events is not a con- stant one. This short duration of the papillary contraction as compared with that of the ventricle wall might be explained by a wave of contraction running through the muscle-fibres of the ventricle wall till it reached the papillary muscles, returning as a reflected wave. The facts at our disposal, however, do not permit of our proving or disproving this theory. It can be seen (in Figs. 4 and 5) that the expansion of the papillary muscles is at first rapid, namely, from the point d to e. During this period the ventricular wall still continues contracted. After e, the expansion of the papillary muscle is more gradual. Immediately after the point t on the papillary muscle curve B there is a more or less rounded shoulder/, indicating that at the commencement of relaxation of the heart-wall there is a slowing of the expansion of the papillary muscle. As the sudden fall of pressure within the heart begins with the commencement of expansion of the heart-wall, and not, to any appreciable extent, with the beginning of expansion of the papillary muscles, it is easy to understand why, while the intraventricular pressure is high, the papillary muscles expand more rapidly than when (after the point e) the intra-ventricular pressure is very much less. The shoulder / is presumably due to the sudden cessation of the pull exerted upon the musculi papillares by the pressure of the blood against the mitral valves.