BIPN 140 LECT #8 1 DKBerg SYNAPTIC TRANSMISSION III. Postsynaptic ResponsesA. NT activation of postsynaptic (ionotropic) receptors1. NT binds to receptor; opens internal channel (“ligand-gated ion channel”). 2. Single channel events: patch-clamp recording, voltage-clamp mode Ohm’s Law: V=IR; I=V/R=gV with I=current, V=voltage, & g=conductance; I = dq/dt where dq = charge transfer (ion flow) across the membrane 3. Neuromuscular Junction (NMJ): endplate currents (EPCs); endplate potentials (EPPs = NMJ PSPs) **FIGURE 5.16a-c**.B. Reversal Potentials (RPs)1. RP = voltage at which EPC reverses direction: from Ohm’s Law: EPC = gACh(Vm-Erev) where EPC=current, gACh=conductance induced by ACh, & (Vm-Erev)=net driving force on the ions flowing, i.e., the difference between membrane potential and the potential at where there is no net ion flow (where the current “reverses” direction) [Recall Nernst equation: RP is like the equilibium potential for the ions flowing during a postsynaptic current (PSC)] **FIGURE 5.17a-c**.**FIGURE 5.18a-d**.
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