تسجيل الدخول

تسجيل

Generation of and Action Potential in the Postsynaptic Neuron

المؤلف:  Kim E. Barrett, Susan M. Barman, Heddwen L. Brooks, Jason X.-J. Yuan

المصدر:  Ganongs Review of Medical Physiology

الجزء والصفحة:  25th E, P126-127

2026-09-22

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The constant interplay of excitatory and inhibitory activity on the postsynaptic neuron produces a fluctuating membrane potential that is the algebraic sum of the hyperpolarizing and depolarizing activities. The soma of the neuron thus acts as an integrator. When the level of depolarization reaches the threshold voltage, a propagated action potential will occur. However, the discharge of the neuron is slightly more com plicated than this. In motor neurons, the portion of the cell with the lowest threshold for the production of an action potential is the initial segment, the portion of the axon at and just beyond the axon hillock. This unmyelinated segment is depolarized or hyperpolarized electrotonically by the current sinks and sources under the excitatory and inhibitory synaptic knobs. It is the first part of the neuron to fire, and its discharge is propagated in two directions: down the axon and back into the soma. Retrograde firing of the soma in this fashion probably has value in wiping the slate clean for sub sequent renewal of the interplay of excitatory and inhibitory activity on the cell.