Contractility can be decreased by increased end-diastolic volume. presence of positive inotropic substances. decreasing inflow of calcium ions. increased end-diastolic volume and presence of positive inotropic substance. increased end-diastolic volume, presence of positive inotropic substance, and decreasing inflow of calcium ions.

Contractility is decrease by elevated or increased Pco2 in insolated preparation, probably as a result of PH change.

Explanation:

Both contractility and heart rate are

decrease by elevated Pco2 in the isolated preparation, probably as a result of pH change. However, in the intact subject the direct depressant effect of carbon dioxide is overshadowed by the stimulant effect mediated through the sympathetic system. Increased Pco2 in artificially ventilated humans, it raises cardiac output and slightly reduces total peripheral resistance,14 therefore blood pressure tends to be increased.

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