Smooth muscle slow-wave potentials

Smooth muscle Slow wave potential changes Pacemaker activity for Myogenic rhythm... 

Slow-wave potentials also involve gradual depolarization of the cell membrane, but these depolarizations do not necessarily reach threshold. Therefore, the depolarization may simply be followed by repolarization back to the initial membrane potential. These slow "wave-like" potentials occur rhythmically and do not lead to smooth muscle contraction. The peak-to-peak amplitude of the slow-wave potential is in the range of 15 to 30 mV. Therefore, under the appropriate conditions, the depolarization phase of the slow-wave potential may, in fact, reach threshold. When this occurs, a burst of action potentials is generated, resulting in muscle contraction. 

Control cycle is one depolarization and repolarization of the transmembrane voltage. Control wave (or slow wave) is the continuing rhythmic electrical activity recorded at any one site. It was assumed to be generated by the smooth muscle cells behaving like a relaxation oscillator at that site. However, recent evidence [Hara et al, 1986 Suzuki et al. 1986 Barajas-Lopez et al, 1989 Serio et al, 1991] indicates that it is generated by a system of interstitial cells of Cajal (ICC) and smooth muscle cells at that site. ECA is the totality of the control waves recorded at one or several sites. Response Potentials (or spikes) are the rapid oscillations of transmembrane voltage in the depolarized state of smooth muscle cells. They are associated with muscular contraction and their occurrence is assumed to be in response to a control cycle when acetylcholine is present. ERA is the totality of the groups of response potentials at one or several sites. 

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