Dromotropy
As Dromotropic (from ancient Greek. Δρόμος dromos : running and τρόπος tropos :, direction change) is called to influence the conduction of the heart . The cells of the AV node are particularly affected .
Positive dromotropy
Positive dromotropy means that the conduction of excitation is accelerated; The reason for this is a sympathetically increased current via the L-type calcium channel , which causes an increased initial steepness of the action potentials. Dromotropy , inotropy (force of contraction) and chronotropy ( frequency of contraction) in the heart are increased via β 1 - and, to a lesser extent, β 2 -adrenoreceptors , and lusitropia (the rate of relaxation) increases (which also contributes to an increase in cardiac output).
Negative dromotropy
Negative dromotropy means a slowdown in the conduction of excitation and is the result of parasympathetic activity. Acetylcholine (just like in the sinus node ) mediates the opening of receptor-controlled potassium channels through a G protein , the current I Kach of which counteracts the depolarization. In this way, strong vagus stimulation can trigger an AV block .
literature
- Robert Franz Schmidt , Florian Lang, Manfred Heckmann (eds.): Physiology of humans . 31st edition. Springer Medizin Verlag, Heidelberg 2010, ISBN 978-3-642-01650-9 , p. 527 .