What lowers the potential of neurons?

[Wolfram Sieber]

Hello group,

up to now i had no special interest about the processes inside
single neurons, but now i have a little question: What lowers the
potential of a neuron?

As far as a i know, signals from neurites go to neurons. These
signals can rise (or lower) the "activation potential" of the
neuron.

"Who" determines if a signal is to rise or to lower the potential?
Is it a special kind of neurit (dentrit or axon) or is it the
shape of a signal, the level of it, or something else?

-- 

best regards, 
Wolfram

@ Cologne, Germany