NRSC 2100 1st Edition Lecture 7 Resting Membrane Potential value can be derived from all E ions Relative Ion Permeabilities of the Membrane at Rest Neurons permeable to more than one type of ion Membrane permeability determines membrane potential Goldman equation Takes into account permeability of membrane to different ions Vm 2 303 RT log PK K o PNa Na o PCl Cl i F PK K i PNa Na i PCl Cl o The Resting Membrane Potential Important points about membrane potentials These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Pump proteins maintain ionic concentration differences between inside and outside of neurons sodium potassium pump and calcium pumps Large changes in Vm Minuscule changes in ionic concentrations Net difference in electrical charge Inside and outside membrane surface capacitance Rate of movement of ions across membrane Proportional to force Vm Eion The Ionic Basis of The Resting Membrane Potential Relative Ion Permeabilities of the Membrane at Rest Resting membrane potential is close to EK because it is mostly permeable to K Membrane potential sensitive to extracellular K Increased extracellular K depolarizes membrane potential General Properties of Synaptic Potentials Quantal Analysis of EPSPs Synaptic vesicles Elementary units of synaptic transmission Quantum An indivisible unit Miniature postsynaptic potential mini Quantal analysis Used to determine number of vesicles released during neurotransmission Neuromuscular junction About 200 synaptic vesicles EPSP of 40 mV or more CNS synapse Single vesicle EPSP of few tenths of a mV QUANTAL ANALYSIS Electrically evoked pre synaptic neurotransmitter release often in the presence of low Ca Measure the number of failures and responses and their amplitudes Results follow a classic statistical distribution Poisson distribution the smallest release unit quantum Transmission of Synaptic Potentials in Dendrites The Contribution of Dendritic Properties to Synaptic Integration Dendrite as a straight cable Membrane depolarization falls off exponentially with increasing distance Vx Vo ex Dendritic length constant In reality dendrites are very elaborate structures that contribute to more complex integrative properties Summary of Synaptic Integration INTEGRATION Summation of PSPs at axon hillock across time
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