Integrated Cardiovascular Control in the Mollusca

The molluscs are a diverse phylum with regard to the form and function of their cardiovascular systems. Recent work on the most advanced class, the Cephalopoda, has shown that regulation of ventricular stroke volume is of paramount importance in the delivery of oxygen to the tissues during exercise. Reviewing the literature indicates that, within the Mollusca, this might be a general strategy in the control of cardiac output. Studies on the isolated heart of the gastropod Busycon show how both intrinsic and extrinsic factors might achieve in vivo output regulation by controlling primarily the end diastolic volume. Again, the details of other studies that support this hypothesis are presented. Last in this paper, the effects of regulatory factors on the electrical activity of the isolated and working Busycon heart are considered in the context of what is known about the ionic bases of muscle excitability.