<Tr> <Td> Cat (Felis) </Td> <Td> Spinal motor neuron </Td> <Td> − 55 to − 80 </Td> <Td> 80--110 </Td> <Td> 1--1.5 </Td> <Td> 30--120 </Td> </Tr> <P> Given its conservation throughout evolution, the action potential seems to confer evolutionary advantages . One function of action potentials is rapid, long - range signaling within the organism; the conduction velocity can exceed 110 m / s, which is one - third the speed of sound . For comparison, a hormone molecule carried in the bloodstream moves at roughly 8 m / s in large arteries . Part of this function is the tight coordination of mechanical events, such as the contraction of the heart . A second function is the computation associated with its generation . Being an all - or - none signal that does not decay with transmission distance, the action potential has similar advantages to digital electronics . The integration of various dendritic signals at the axon hillock and its thresholding to form a complex train of action potentials is another form of computation, one that has been exploited biologically to form central pattern generators and mimicked in artificial neural networks . </P> <P> The study of action potentials has required the development of new experimental methods . The initial work, prior to 1955, was carried out primarily by Alan Lloyd Hodgkin and Andrew Fielding Huxley, who were, along John Carew Eccles, awarded the 1963 Nobel Prize in Physiology or Medicine for their contribution to the description of the ionic basis of nerve conduction . It focused on three goals: isolating signals from single neurons or axons, developing fast, sensitive electronics, and shrinking electrodes enough that the voltage inside a single cell could be recorded . </P> <P> The first problem was solved by studying the giant axons found in the neurons of the squid (Loligo forbesii and Doryteuthis pealeii, at the time classified as Loligo pealeii). These axons are so large in diameter (roughly 1 mm, or 100-fold larger than a typical neuron) that they can be seen with the naked eye, making them easy to extract and manipulate . However, they are not representative of all excitable cells, and numerous other systems with action potentials have been studied . </P>

Which two ions move in and out of a neuron during an action potential