Electric signals between individual cardiac cells regulate heartbeat


Date:
July 13, 2021
Source:
American Institute of Physics
Summary:
Researchers provide an update on how electrical impulses in the
heart travel from cell to cell. The connections between cells
forming the low resistance pathway and facilitating the current
flow are called gap junctions. Each consists of many channels,
which are formed when specific proteins from one cell dock and
fuse to the proteins from another cell.

The scientists delve into the properties of gap junctions and
their constituent proteins.



FULL STORY ==========================================================================
The rhythm in a working heart is regulated by electrical
impulses. Disturbances of this bioelectrical process can result in
cardiac arrhythmias, or irregularities in heartbeat -- a common ailment
that can lead to illness and death.


==========================================================================
In Biophysics Reviews, by AIP Publishing, researchers from Harvard Medical School provide a state-of-the-art update on how electrical impulses in
the heart travel from cell to cell.

A functioning heart contracts to pump blood to the body and the
lungs. Within the heart, a pacemaker acts as an electrical clock, sending
out a signal that tells the heart when to contract. The whole muscle
moves together, because each individual cell inside of it contracts in
a coordinated manner and within a short time interval.

In order to do so, the initial electrical impulse, sent by the pacemaker, rapidly spreads through cells across the heart.

"If one cell is excited electrically and the other is not, the excited
cell becomes positively charged inside, and the resting cell is still negatively charged inside. As a consequence, a voltage gradient builds
up between the cells," said author Andre' Kle'ber. "If you have a voltage gradient and a pathway with a low electrical resistance, a local current
will flow." The connections between cells forming the low resistance
pathway and facilitating the current flow are called gap junctions. Each consists of many channels, which are formed when specific proteins from
one cell dock and fuse to the proteins from another cell. Kle'ber said
the fusing proteins look like placing the tips of your fingers on one
hand to the fingers on the other hand.

The scientists delve into the properties of gap junctions and their
constituent proteins, the so-called connexins. Kle'ber said one reason
gap junction channels are interesting is because they are a highly dynamic system in equilibrium. The creation, or synthesis, of the channels equals
the destruction.

"The turnover is very short," he said. "On one hand, the system is very
stable during your whole life. On the other hand, if you measure it, it
is constantly cycling in periods of a few hours." The proteins found
in gap junctions are important for processes not directly related to
cell-cell connections, like mitochondrial function, which creates energy,
and trafficking, which transports molecules from the site of synthesis
to their site of action in the cell interior.

"You have to refrain from the idea that if you define the role
of a protein in the body, that it has only a single function,"
said Kle'ber. "Nature is much, much smarter than human beings." ========================================================================== Story Source: Materials provided by American_Institute_of_Physics. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Andre' G. Kle'ber, Qianru Jin. Coupling between cardiac cells--An
important determinant of electrical impulse propagation and
arrhythmogenesis. Biophysics Reviews, 2021; 2 (3): 031301 DOI:
10.1063/ 5.0050192 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/07/210713120330.htm

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