From voltage-gated currents to action potentials and dendritic propagation
Current clamp: vary the amplitude and duration of the injected current to examine spike threshold and waveform. Enable Refractory period to test how closely two action potentials can occur.
Voltage clamp: command membrane voltage directly and inspect the underlying ionic currents. TTX removes the fast Na⁺ current and TEA removes the delayed-rectifier K⁺ current; the recovery protocol explores Na⁺-channel inactivation.
Stick dendrite: inject the soma and compare dendritic Na⁺ densities of 0%, 20%, 40%, and 100%. Low density produces decremental invasion, whereas increasing Na⁺ density progressively recruits regenerative propagation. Drag the time slider or select Animate to follow the membrane-voltage profile from soma to distal dendrite; the vertical line in the voltage graph marks the same moment. Set both dendritic Na⁺ and K⁺ to 0% for a fully passive cable. The stick is a generic active cable using squid HH kinetics, not a quantitative model of a layer-5 pyramidal neuron.
Hodgkin AL & Huxley AF (1952), A quantitative description of membrane current and its application to conduction and excitation in nerve. Journal of Physiology 117:500–544.
Häusser M, Stuart G, Racca C & Sakmann B (1995), Axonal initiation and active dendritic propagation of action potentials in substantia nigra neurons. Neuron 15:637–647.
Vetter P, Roth A & Häusser M (2001), Propagation of action potentials in dendrites depends on dendritic morphology. Journal of Neurophysiology 85:926–937.