Endogenous electrical currents

Endogenous electric fields were measured at human skin wounds in the mid-nineteenth century. German physiologist Emil Du-Bois Reymond, using a self-built galvanometer, measured electric currents of 1 pA flowing out of a skin wound on his own finger (1, 2). 

Fig. 1. Endogenous electric fields at epithelial wounds, (a) Schematic showing electric current flow (arrows) driven out the wound site by the transepithelial potential difference. (b) Small cut on human finger tip (/efl) and vibrating probe measuring current at the wound site (right), (c) Electrical currents at human finger wound, (b, c) are modified from (6).

Nuccitelli, R. (1992) Endogenous ionic currents and DC electric fields in multicellular animal tissues. Bioelectromagnetics Suppl 1, 147-157. 

All electric currents are accompanied by magnetic fields. With the invention of the Superconducting Quantum Interference Device as an extremely low magnetic field (10 T) detector, it has become possible to measure the magnetic fields from the small endogenic currents of the body, even from the small sources in the heart and the central nervous system. This has opened up a whole new field of measurements analogous to their electric counterparts MKG (EKG), MEG (EEG), and so on. However, these interesting subjects are outside the scope of this book, and the reader is referred to the book by Malmivuo and Plonsey (1995). 

Quantitatively, the binding of Ca2+ to the glycocalyx is of secondary importance compared to that bound by phospholipid elements. The glycocalyx does play a significant role in the determination of myocardial cell Ca2+ permeability (20, 21). Upon arrival of the appropriate electrical stimulus T ction potential), Ca2+ crosses the sarcolemma and is the principal cation responsible for a current called the "slow inward current" (lsi) (3-2, 22, 23, 24). Calcium is conducted across the sarcolemma through channels or pores which are controlled by the phosphorylation of sarcolemmal and sarcotubular proteins. Cardiac sarcolemma and sarcoplasmic reticulum are phosphorylated by exogenous and endogenous cyclic adenosine 5 -5 - monophosphate (cAMP)-dependent protein kinases (25, ... 

Figure 6 shows the difference spectra of the catholyte before and after electrolysis. Complete reduction was achieved after a few minutes. A high mediator concentration was necessary to achieve a measurable current density. Since endogenous oxygen is always present in the mitochondria, a coulometric measurement of the amount of electricity, consumed solely for the reduction of the mitochondria was not possible. A simultaneous reduction of the oxygen took place, partly to the superoxide anion, which in turn could reduce the cytochromes in the mitochondria. This chemical reduction is slower and so all of the electricity consumed could be accounted for as being used in the reduction of the cytochromes. 

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