doi: 10.1161/01.RES.0000251936.26233.0d
© 2006 American Heart Association, Inc.
Editorials |
Gap Junctions
Clarifying the Complexities of Connexins and Conduction
From the Head of Cardiac Electrophysiology, Imperial College, Department of Cardiology, St Mary’s Hospital, Praed Street, London.
Correspondence to Nicholas S. Peters, MD FRCP FHRS, Professor of Cardiology, Head of Cardiac Electrophysiology, Imperial College, St Mary’s Hospital, London; Dept of Cardiology, St Mary’s Hospital, Praed Street, London W2 1NY. Email n.peters@imperial.ac.uk
See related article, pages 1216–1224
Key Words: gap junction • connexin • conduction • atrium
An extract of the first 250 words of the full text is provided, because this article has no abstract. |
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Introduction |
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In the late 19th century microscopy and early physiological experimentation gave rise to the apparent paradox that although cardiac muscle is made up of individual cells, it behaves as a single continuous functional unit. The explanation had to be that a component of the individual cells was responsible for coupling them together and coordinating their function to provide one continuous electromechanical unit. In the 1960s high resolution microscopy identified the likely membrane specialization responsible for this, and the functional properties of what later became known as the "gap junction" started to be determined by experimentation in the 1970s.
Gap-junctional membrane offers relatively low resistance to current flow, several orders of magnitude lower than ordinary cell membrane. But in passing through the cytoplasmic pathway from cell to cell in whole tissue, gap junctions remain relatively resistive discontinuities to the passage of ions and electrical charge through this cytoplasmic pathway, presenting a resistance across the gap junction (of nanometre width) approximately equivalent to that of the column of cytoplasm of an entire cell length (
100 µm).
Although electrophysiological, molecular and genetic techniques have been used to provide a very substantial body of knowledge of gap-junctional structure and function the precise mechanism by which the action potential is propagated from cell to cell, and the precise role of the gap junction remains unclear. It is thought to determine how much depolarizing current can pass from a depolarized cell to its neighbor in the process of impulse propagation, thus providing continuity across the
Related Article:
Circ. Res. 2006 99: 1216-1224.
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