Posterior-lateral view of a beating heart (crayfish)
In order for the heart to work as a pump, the intake
valves (ostia) must be closed and the outlet valves (cardio-arterial
valves) opened during systole, and vice versa during
The closure of the ostia is controled by the cardiac ganglion neurons. The tension of the cardio-arterial valves are regulated by the extrinsic nerves from the CNS and hormones.
It has been reported by some investigators that the distribution of blood flow is controled by changing the tension of each cardio-arterial valve.