The papillary muscles contract after the other ventricular muscles so that they can take up the slack on the chordae tendineae before the full force of ventricular contractions sends blood against the atrioventricular (AV) valve flaps. true/false

False

Explanation:

The papillary muscles of both right and left ventricles began to contract shortly before the other ventricular muscles (systole) so that they can take up the slack on the chordae tendineae as the full force of ventricular contractions sends blood against the atrioventricular (AV) valve flaps.

They prevent the backward flow of blood to atria from ventricles. So if they contract after the ventricle systole they would not be able to perform their job.