Physiology of the cardiac muscle (see experimental arrangement)

Three types of muscles in the heart

    There are two types in the cardiac muscles: The ordinary cardiac muscles and the ostium muscle. They are both controled by common motor neurons in the cardiac ganglion. There also are the cardio-arterial valves between the ventricle and the arteries. The muscles of the cardio-arterial valves are regulated by motor nerves from the CNS.
... also see the heart as a pump

Coodinated contraction of cardiac muscles

These pictures are the snapshots of crayfish heartbeat taken at the interval of 1/15 sec. The lateral ostium (valvular opening) and the poterior end of the heart are visible in each frame. Closure of the ostium starts just before the contraction of the heart wall (GIF movie).
    Acting as a simple pump, quick closure of the valuvular openings is important to pump out efficiently the hemolymph to the arteries. The closure of the ostia is induced by rapid contraction of the ostium muscles which is innervated by the motor neurons in the cardiac ganglion. Controled by the same motoneurons, how can the ostium muscles contract faster than the cardiac muscle?     You will see my results at 5th International Congress of Comparative Biochemistry and Physiology on August 23-28 1999 in Calgary, Alberta.