Related Experiment Video
Updated: Aug 21, 2026

Isolation of Human Atrial Myocytes for Simultaneous Measurements of Ca2+ Transients and Membrane Currents
Published on: July 3, 2013
Criticality in the relaxation phase of a spontaneously contracting atria isolated from a frog's heart
Y F Contoyiannis1, F K Diakonos, C Papaefthimiou
1Department of Physics, University of Athens, GR-15771 Athens, Greece. ikonto@cc.uoa.gr
Abstract:
We investigate the spontaneous contraction generated by the atria of a frog's heart isolated in a physiological solution. In the relaxation phase, the recorded time series for two different sampling rates possesses an intermittent component similar to the dynamics of the order parameter's fluctuations of a thermal critical system belonging to the mean field universality class. This behavior is not visible through conventional analysis in the frequency space due to the presence of Brownian noise dominating the corresponding power spectrum.
Related Concept Videos
Electrophysiology of Normal Cardiac Rhythm
Cardiac Action Potential
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
Specialized Characteristics of Cardiac Muscles
Cardiac muscle cells are smaller than skeletal muscles, averaging 10–20 mm in diameter and 50–100 mm in length. However, they have large energy demands for continuous contraction and relaxation. This energy is almost exclusively derived from aerobic metabolism of energy reserves in...
Relaxation of Skeletal Muscles
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open.

