THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -Because there is finite time available for ejection ( 200 msec), changes in ejection velocity alter the stroke volume-increased ejection velocity increases stroke volume, whereas reduced ejection velocity decreases stroke volume.

Detailed explanation-2: -An increase in preload results in an increased force of contraction by Starling’s law of the heart; this does not require a change in contractility. An increase in afterload will increase contractility (through the Anrep effect). An increase in heart rate will increase contractility (through the Bowditch effect).

Detailed explanation-3: -Positive inotropic factors include circulating catecholamines and the cardiac sympathetic nerves, whereas negative inotropic factors include severe anoxia, acidosis, and the volatile anesthetics.