3.9 Experimental evidence

3.9.2 Axon

We have a constant voltage at the end of the tube; the ”slow” current ”flowing out” from the tube increases and appears on the membrane, establishing the illusion that the conductance of the tube increases. Resistance/conductance cannot be interpreted when charge carriers flow into the resistor (and this is the case with the axon) from the environment: the ”slow” current produces a different behavior (increases the number of charge carriers n), see Eq. (2.28).

Figure 3.22: A) PSP decay (curve 1) and the decay after an injected depolarizing current pulse (curve 2) recorded in the same cell. B) Voltage traces (upper and middle) from which the curves in A were derived, together with the current record (lower) for the pulse. The colored marks and diagram lines are calculated using the model’s ”slow” current. Measurement data (with black) are reproduced from Fig. 4 of [83] (”©[1991] Society for Neuroscience” ).
Figure 3.23: The ”ghost image” formed by the delayed membrane current: the origin of the AP. The finite-speed ions transferred on the finite-size surface of the membrane: Kirchoff’s Law in biology. The assumed delay time between input and output currents is 0.49⁢m⁢s, the function form and its parameters are displayed in Fig. 3.25.
Figure 3.24: The time course of voltage and current a clamping experiment, calculated numerically for switching the clamping on and off.
Figure 3.25: Time course of the post-synaptic potential evoked by a single AP. The colored marks and diagram lines are calculated using the model’s ”slow” current. Measurement data reproduced from Fig. 2 of [83] (”©[1991] Society for Neuroscience”).