The nerve impulse is the basis of all human thoughts and emotions, and of all sensations and movements. As such, it has been the subject of scientific enquiry for more than two centuries, beginning with Galvani’s chance observation that a frog’s leg twitched in response to an electrostatic discharge nearby. From being a metaphysical concept, the impulse became a phenomenon that could be recorded and have its velocity determined. However, the nature of the brief permeability changes in the nerve membrane that made the impulse possible, and of the way in which the nerve endings influenced the ex ... More

The nerve impulse is the basis of all human thoughts and emotions, and of all sensations and movements. As such, it has been the subject of scientific enquiry for more than two centuries, beginning with Galvani’s chance observation that a frog’s leg twitched in response to an electrostatic discharge nearby. From being a metaphysical concept, the impulse became a phenomenon that could be recorded and have its velocity determined. However, the nature of the brief permeability changes in the nerve membrane that made the impulse possible, and of the way in which the nerve endings influenced the excitability of connecting neurons, remained problems that taxed the ingenuity of physiologists for many years. An important breakthrough was the discovery of giant nerve fibres in the squid, fibres large enough for new techniques to be employed, as in the voltage-clamp experiments of Hodgkin and Huxley immediately after World War II. The story culminates with the recent discovery of the 3-dimensional structure and detailed functioning of the ion channels, following MacKinnon’s X-ray diffraction studies, and with the revelation that a host of clinical disorders result from malfunction of the ion channels.