THE INITIATION OF IMPULSES IN CARDIAC MUSCLE

Abstract

On recording monophasic potentials in strips of cardiac muscle from mammals and from the turtle it was found that a slow rise in negativity at the pacemaker precedes each spontaneous beat. After injury a regular series of incrementing oscillations often initiate impulses. Such oscillations usually give rise to series of beats separated by periods of rest (Luciani periods). Impulses are followed by positive or negative after-potentials, and often in injured muscle by decrementing oscillations. If large enough the latter initiate new impulses. Acetylcholine diminishes the local potentials except in the ventricle, but influences their frequency only moderately or not at all. Neither acetylcholine nor adrenalin influences the frequency of the oscillations.