However, if a laboratory axon is stimulated in its middle, both halves of the axon are " fresh ", i . e ., unfired; then two action potentials will be generated, one traveling towards the axon hillock and the other traveling towards the synaptic knobs.
42.
Both inhibitory postsynaptic potentials ( IPSPs ) and excitatory postsynaptic potentials ( EPSPs ) are summed in the axon hillock and once a triggering threshold is exceeded, an action potential propagates through the rest of the axon ( and " backwards " towards the dendrites as seen in neural backpropagation ).
43.
At the axon hillock of a typical neuron, the resting potential is around 70 millivolts ( mV ) and the threshold potential is around 55 mV . Synaptic inputs to a neuron cause the membrane to hyperpolarize; that is, they cause the membrane potential to rise or fall.
