Action Potentials: Mechanisms and Propagation

This lecture covers the fundamental mechanisms of action potentials in neurons, detailing the electrical properties of neuronal membranes. It begins with the Goldman equation, which determines the reversal potential of a membrane by considering the concentrations and permeabilities of various ions. The instructor explains the process of depolarization and hyperpolarization during action potentials, emphasizing the role of sodium and potassium channels. The lecture also discusses the refractory periods, highlighting the absolute and relative phases that affect the generation of subsequent action potentials. Insights from historical experiments by Hodgkin and Huxley using the squid giant axon are presented, illustrating the relationship between ionic conductance and action potential amplitude. The propagation of action potentials along axons is explained, including the factors that influence conduction speed, such as axon diameter and myelination. The lecture concludes with an explanation of saltatory conduction, where action potentials jump between nodes of Ranvier, enhancing the speed of signal transmission along myelinated axons.