Heart rate variability are needed to address the LF component (with a lower bound of 0.04 Hz). Although time domain methods, especially the SDNN and RMSSD methods, can be used to investigate recordings of long durations, a substantial part of the long-term variability is day–night differences. Thus, long-term recordings analyzed by time domain methods should contain at least 18 hours of analyzable ECG data that include the whole night. Although cardiac automaticity is intrinsic to various pacemaker tissues, heart rate and rhythm are largely under the control of the autonomic nervous system. The parasympathetic influence on heart rate is mediated via release of
Muscle contraction calcium buffers moderate this fall in concentration, permitting a relatively small decrease in free concentration in response to a large change in total calcium. The falling concentration allows the troponin complex to dissociate from the actin filament thereby ending contraction. The heart relaxes, allowing the ventricles to fill with blood and begin the cardiac cycle again. In annelids such as earthworms and leeches, circular and longitudinal muscles cells form the body wall of these animals and are responsible for their movement. In an earthworm that is moving through a soil, for example, contractions of circular and longitudinal muscles occur reciprocally