This lecture discusses the concept of membrane potential and its significance in neuronal function. It begins with an introduction to the equilibrium potential and the role of semipermeable membranes in establishing ionic gradients. The instructor explains how the difference in charge across the plasma membrane generates an electrical potential known as membrane potential. Through various experiments, the lecture illustrates how potassium ions move across a membrane, leading to the establishment of equilibrium potential. The Nernst equation is introduced as a mathematical representation of the reversal potential for specific ions, highlighting the balance between electrical and chemical gradients. The lecture further explores the Goldman equation, which accounts for multiple ions and their permeabilities, providing a comprehensive understanding of resting membrane potential in real physiological conditions. The discussion emphasizes the importance of these equations in predicting ion flow and understanding neuronal signaling, ultimately contributing to the broader field of neuroscience.