THE RELATION OF CONTRACTION OF DIFFERENT REGIONS OF THE VENTRICLE OF THE TURTLE TO THE RISE OF INTRAVENTRICULAR PRESSURE

Abstract

The rise of pressure in the ventricle of the turtle during systole, is characterized by an initial slow rise, amounting to a few mms. of Hg and lasting about 0.12 of a sec. This is followed by an abrupt increase of the pressure gradient. Local shortening of various regions on the anterior surface of the ventricle begin during the initial period of pressure rise or within an interval of several hundredths of a sec. after its termination. Shortening in all regions thus occurs before the pressure has risen sufficiently to force blood into the great vessels and reduce the vol. of the ventricle. This shortening is made possible by change in shape of the ventricle early in its contraction to approximately that of a sphere. Myograms from the surface of the ventricle of the turtle hence afford an adequate criterion for the onset of the local shortening process and for a comparison of electrical and mechanical events.