Can someone explain the voltage curves at the five measuring points A to E?

Good Morning,

A shows you an axon without myelin separation (a distinctive nerve fiber), in which there is a continuous excitation line. There are many action potentials behind each other (current summation).

D shows you an electrode at the cell soma near the synapse belonging to Axon A. The oscilloscope shows here a hyperpolarization (lower millivolt values ​​​​than in the resting potential). From this, you can conclude that Axon A is a so-called inhibitory synapse that triggers inhibitory post-synaptic potentials (IPSPs) at the cell soma.

B is a myelin-encased axon (a distinctive nerve fiber), in which a saltatory excitation line therefore occurs. Here, too, several action potentials were fired one after the other, as can be seen on the oscilloscope (current summation).

C shows a further electrode in the celloma. Here it can be seen on the oscilloscope that there is a build-up depolarization at the soma membrane. This means that Axon B leads to a stimulating synapse that triggers post-synaptic potentials (EPSPs) in the soma.

The IPSPs of the inhibiting synapse and the EPSPs of the exciting synapse now spread over the soma and thus reach the axon hill of the nerve cell.

There is a third electrode in the celloma (E). The oscilloscope shows that here a hyperpolarization occurs, followed by a small (underswelling) depolarization. This is achieved by the spatial summation of the IPSPs and EPSPs.

In any case, the spatial summation of the signals leads to the axon hill of the cell under consideration not being sufficient to trigger an action potential. And that is exactly what shows the derivation of the signal at the axon, because the oscilloscope image at F shows no signal (rest potential).

All right?

LG from the Waterkant