Difference between revisions of "Draft:Two Forms of Electrical Transmission Between Neurons"

=== Introduction ===

It has been argued that the function of the nervous system is to support movement and that it evolved because of its usefulness to organisms in navigating their environment (Llinás, 2001). Early observations established that nerves were required for muscle contraction. However, the mechanism underlying this interaction was unknown. An old, predominant, idea embraced by Rene Descartes was that muscle contraction resulted from the action of “animal spirits” running through hollow nerves (Piccolino, 1998; Finger, 2005). This and other speculative ideas were later disproved, leading to the consideration of alternative mechanisms. One of them was electricity (Franklin, 1751). The use of electricity for therapeutic purposes was popular in the second part of the 18th century, and electricity was capable of eliciting muscle contraction. In addition, because of its high travel velocity, electricity was ideally suited to be the agent responsible for nerve action, as some hypothesized (Finger, 2005). Furthermore, experimental evidence showed that certain fish were capable of generating electricity. All this preceding work and speculations paved the way to the studies conducted by Galvani (1791) which demonstrated that nerves and muscles generate electricity (“bioelectricity”) and, therefore, that electricity was the mysterious fluid or “animal spirit” responsible for nerve conduction and muscle contraction (Piccolino, 1998; Finger, 2005). We know now that these electrical currents result from the movement of charged ions across the cellular membrane following their electrochemical gradient (Hodgkin and Huxley, 1952; Armstrong, 2007). Galvani’s seminal studies led to the foundation of electrophysiology and to the discovery that brain function and, hence, animal behavior, depends upon electrophysiological computations, the only operational mode fast enough to support the required time frame of decision making by neural circuits. In other words, as emphasized by Llinás, electricity makes us who we are (Sohn, 2003).