And the heartbeat goes on ... and now we know why

William Atkins
Wednesday, 28 January 2009 21:15

Science - Biology

British researchers have determined what triggers the beat of the heart muscle. This discovery will help medical professionals learn more why the heart sometimes has problems so such heart diseases can be alleviated in the future.


Dr. Yin-Biao Sun, of the Randall Division of Cell and Molecular Biophysics at King’s College London (United Kingdom), along with Fang Lou (University of Hertforshire) and Malcolm Irving (King’s College London), wrote the results of their research in the Journal of Physiology on January 1, 2009.

The title of their paper (volume 587, number 1, pages 155-163, doi: 10.1113/jphysio.2008.164707) is “Calcium- and myosin-dependent changes in troponin structure during activation of heart muscle.”

They found that the heartbeat is controlled by large numbers of calcium ions that cause thin filaments of heart muscle cells, which are made up of the proteins actin and myosin, to force up against each other and, then, contract into a different shape.

Specifically, they state in the paper's abstract, “Each heartbeat is triggered by a pulse of intracellular calcium ions which bind to troponin on the actin-containing thin filaments of heart muscle cells, initiating a change in filament structure that allows myosin to bind and generate force.”

In other words, each heartbeat is triggered by outpouring of calcium ions that attach themselves onto troponin (three regulatory proteins that provide for muscle contraction in cardiac muscles and skeletal muscles) within millions of thin filaments, which contain actin as part of heart muscle cells.

When these calcium ions attach to the actin, the filaments change their structural shape (they contract), which allows myosin to bind and, thus, produce the force necessary to initiate a heartbeat.

Page two continues with more on their heartbeat study.