205textnotes09 - Trigger zone Depolarization is needed to...

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Trigger zone: Depolarization is needed to excite (cause an action potential) a nerve cell. excitatory postsynaptic potential (EPSP) : a depolarizing graded potential which drives the membrane potential towards threshold. inhibitatory postsynaptic potential (IPSP) : a hyperpolarizing graded potential which drives the membrane potential away from threshold. If multiple signals arrive at the trigger zone they are summed (superimposed). If multiple stimuli arrive simultaneously this is call spatial summation , if the arrive at slightly different times you have temporal summation . THE NERVOUS SYSTEM Chapter 8: Neurons: cellular and network properties Part D. Action Potentials: Action potentials are rapid signals that pass along the axon to the axon terminal, and differ from graded potentials in several ways: (Figure 8-9) 1) Action potentials are identical to each other and 2) they do not diminish in strength as they travel through the cell. The action potential is a large depolarizing signal up to 110 mV in amplitude.
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