PowerPoint PresentationBlank Slide for taking lots of good notes on slide 17-1Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 917-117-2Blank Slide for taking lots of good notes on slide 17-117-35. Propagation of action potentialsAction potential travels down membrane as wave of Na+ depolarization, followed by wave of K+ repolarizationNa+ entry depolarizes ready membrane aheadK+ exit repolarizes refractory membrane behindNa+K+Na+K+Na+K+Na+K+Na+K+Na+K+Na+K+Na+K+Na+K+Na+K+Na+K+K+Na+Depolarization17-4Mechanisms exist to speed action potentialsincrease axon diameterinsulate axon: myelinsaltatory conduction: a.p. jumps between nodes17-5Synapses between neurons have a lot in common with the NMJ: But also some important differences17-6Response of postsynaptic cell depends on type of channel the neurotransmitter receptor is linked to1. Channel conducts Na+, depolarization=excitatory postsynaptic potential (epsp)2. Channel conducts K+,Cl-, hyperpolariztioninhibitory postsynaptic potential (ipsp)17-7Multiple postsynaptic potentials must be produced to trigger the postsynaptic neuron to thresholdSummation: current of graded potentials can sum17-8Democratic nature of nerve transmissionaction potential will not occur in postsynaptic cell unless it receives multiple epsps and few ipspsSummation occurs at axon hillock (initial segment)If hillock partially depolarized: facilitation17-9Neurotransmitters:Just a few examples of the many. What do they have in common?1. Acetylcholine: skeletal muscle control2. Biogenic amines (amino acid derivatives)norepinephrine, dopamine, seratonin3. Amino acidsGABA,