In the coronary circuit, the myocardium performs the coordinated contractions that pump blood out of the ventricles. these contractions are the
a. coronary arteries.
b. heart rate.
c. heartbeat.
d. aorta.

Asoccer mom is driving her 75 year old grandmother and her 9 year old daughter home after the game. the grandmother and daughter were both in the back seat and both were wearing their seat belts. a car ran a red light in front of them, causing them to t-bone that car on the passenger side. fortunately there were no serious injuries, but the grandmother did sustain several rib fractures. the mother, daughter and driver of the at-fault car were shaken up but unhurt. what are some possible reasons that the grandmother sustained rib fractures while the other victims did not?