Geometry plays a central role in electrophysiology by shaping how local ionic currents spread across cell membranes. Yet cells are often modeled using a single transmembrane voltage, assuming that they are electrotonically compact. Using theory and simulations of a spherical membrane vesicle driven by current through a single ion channel, I will examine when and how this approximation emerges.

At early times, the voltage response remains local and insensitive to the overall membrane geometry. Under sustained current, it spreads to the vesicle scale, where the finite and closed geometry drives a crossover to nearly uniform capacitive charging and a single membrane voltage. I will also introduce a nonlocal cable equation and identify the conditions under which conventional cable theory is recovered.

Biography

Dr. Sirui Ning received his DPhil in Theoretical Physics from the University of Oxford, where he studied string theory under the supervision of Prof. Joseph Conlon. He is currently a Gordon and Betty Moore Foundation Postdoctoral Fellow at UC Berkeley, working with Prof. Karthik Shekhar and Prof. Kranthi Mandadapu. His research lies at the intersection of membrane biophysics and theoretical neuroscience, using theory and computation to study bioelectricity, membrane electromechanics, and the physical mechanisms that connect ion channel activity to electrical signaling in neurons.

Inviter: Hai-Jun Zhou