The membrane as an RC circuit
Three tabs on the membrane as an RC circuit: charging and discharging under a current pulse, how capacitance scales with cell size, and how much charge (Q = CV) it takes to change the membrane potential.
Teaching · Interactive tools
A set of self-contained simulators built for our Biophysics and Neurophysiology courses. Each one recreates a classic electrophysiology experiment interactively — from the squid giant axon to long-term potentiation in the hippocampus — so that students can explore the mechanisms hands-on, with no software to install.
Twelve simulators, one common thread
The simulations follow the classic path of an electrophysiology course: first the generation and propagation of the action potential, then the single ion channel that makes it possible, and finally synaptic transmission — quantal, central and plastic, both short- and long-term. Each simulator runs directly in the browser.
Three tabs on the membrane as an RC circuit: charging and discharging under a current pulse, how capacitance scales with cell size, and how much charge (Q = CV) it takes to change the membrane potential.
Two ways of measuring a membrane capacitor: a classic RC circuit on the lab bench, and the whole-cell membrane test of a patch-clamp amplifier. Compare the time constant τ and the nominal capacitance with the values measured from real components.
A reconstruction of the Hodgkin–Huxley model: voltage clamp, the membrane action potential and propagation along the axon, with interactive plots and exportable data tables.
A patch-clamp amplifier connected to a model neuron (CA1 pyramidal, PV⁺ fast-spiking interneuron or dentate gyrus granule cell). Seal, break in and record in V-Clamp, I = 0 or I-Clamp — with access resistance, C-fast, C-slow and Rs compensation, filtering and noise applied in real time. Includes the Ra/Rm/Cm measurement exercise and the F–I curve with action potential count and instantaneous frequency.
Stochastic activity of a voltage-gated Na⁺ channel (C⇌C⇌O→I scheme): single trace, multiple sweeps and ensemble average, with cursors to measure the size of the current step.
A voltage-clamp simulation of K⁺ channel gating currents: oscilloscope-style traces of IK and Igating, alongside the G-V and Q-V curves. Includes recording noise and an option to average multiple sweeps of the gating current.
A Hodgkin–Huxley membrane under a sustained current pulse, firing a train of action potentials. Switch the delayed rectifier and an A-type K⁺ conductance (Connor–Stevens) on or off independently, and see their effect on spike shape, the afterhyperpolarization and the f–I relationship.
A replica of the Katz & Miledi / del Castillo & Katz experiments: evoked end-plate potentials, a histogram of quantal amplitudes, and a zero-calcium condition to observe failures and quantal units.
Postsynaptic currents at a central synapse with AMPA and NMDA components, Mg²⁺ block and low-N binomial release, on a virtual oscilloscope with realistic recording noise.
A three-channel oscilloscope — presynaptic action potential, presynaptic intracellular Ca²⁺ and postsynaptic EPSP/fEPSP — showing short-term facilitation during pulse trains. Control the number of pulses, the frequency and the postsynaptic time constant (τ).
LTP induction in stratum radiatum by tetanization, TBS or low-frequency pairing, read out as fEPSP slope or EPSC amplitude, with control over NMDA/Mg²⁺ coincidence detection.
LTP at the perforant path–dentate gyrus synapse, where strong feedforward GABAergic inhibition of granule cells makes induction harder. Protocol: 4 trains of 100 pulses in 1 second, 5 minutes apart.
Use
Each simulation is a self-contained HTML file: it needs no installation or server connection, and can run directly in the browser or be downloaded for offline use. They are designed as support material for Biophysics and Neurophysiology classes, and can be used live in class or assigned as preparation or review.