While excitation-contraction coupling in the heart has been studied extensively, the reverse processes of mechanical influences on electrogenic characteristics (mechano-electric feedback) have been investigated less . One model situation can be induced by applying negative pressure under a suction electrode . This electrode records a monophasic action potential (MAP), which is the electrogram from the epicardium or endocardium. The details of its development are not entirely understood .Mechanical pressure (or suction) exerted against the myocardium depolarizes and inactivates the group of cells subjacent to the electrode while leaving the adjacent cells largely unaffected. There is an electrical gradient between the depolarized and inexcitable cells subjacent to the electrode and the adjacent normal cells. MAP recording reflects the voltage time course of normal cells that bind to the surface of the volume of cells depolarized by contact pressure. Thus, both depolarized (injured) and active (uninjured) cells contribute equally to the genesis of boundary current, which produces the MAP field potential. It would be of theoretical interest and practical importance to register directly the membrane potentials (MPs) beneath the depolarizing electrode . Your online shopping for buy levlen birth control is going to be as advantageous as never before.