The high performance of our nervous system is based on a fundamental principle: the formation and controlled modulation of an electrical potential across the cell membranes of neurons. In the ISC course ‘Neurobiology’, participants analysed the resting membrane potential of individual cells as well as active and passive potential changes. They learnt how the membrane potential can be influenced chemically and electrically and concluded what this means for the function of the nervous system and its health maintenance. Phototransduction was analysed by means of self-experiments and recording of retinograms in the migratory locust. Extracellular recording of action potentials from the central nervous system was used to illustrate some aspects of signal processing in the visual system of the locust.