BMS 300 1st edition Lecture 22 Outline of Last Lecture I. From generator potential to action potential to chemical synapses-generating action potential in the trigger zone1. the generating potential >voltage gated channels -frequency coding 1. transmission of information by all or nothing invariant signals >bout duration >frequency within a bout -delivery to the next neuron >the chemical synapsesII. Why a chemical synapse-some history of the concept III. Structure of a synapse -presynaptic element >neurotransmitter -synaptic clapt -post synaptic >the ligand-gated channels as receptorsOutline of Current Lecture 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.IV. Structure of the synapse -presynaptic -cleft -post synaptic V. Generation of the excitatory post synaptic potential -neurotransmitter release 1. machinery of exocytosis >V-snare >T-snare 2. fate of the neurotransmitter >the ligand gated channel >receptor ligand binding >channel opening/ion flow >uptake of neurotransmitter by glia VI. Propagation of the epsp -graded potential -decrementing potential -summation of the trigger zone -role of the membrane resistance in passive membrane VII. Inhibition -the IPSP -role of channels>inhibitory neurotransmitters Current LectureRecap last lecture: -presynaptic: full of synaptic vesicles, they were nestled up against the membrane right by the v-gated calcium channels >extension of the conductile region -synaptic cleft: gap in between the pre and post synaptic with astrocytes surrounding it>concentration of Ca is 2-3milimol -we use the chemical gradient to drive the Calcium into the cell >Ca triggers neurotransmitter release via exocytosis -the synaptic vesicle fuses with the plasma membrane by exocytosis which releases a neurotransmitter -each of the vesicles contains around 10,000 molecules of neurotransmitters -on the postsynaptic cell there are receptors: neurotransmitter receptors >they are also ligand gated channels >the binding at this site causes the gate of the channel to open >the charge changes the orientation of the protein which allows the channel to open where sodium ions can move >cation channels -the sodium provides a depolarization -this happens in the central nervous system -the typical excitatory post synaptic potential (EPSP): is about 1mvSNARE hypothesis for neurotransmitter release-there are vesicles close to the membrane and around v-gated channels -there are also v-gated calcium channels -in the vesicular membrane there is a transmembrane protein called vesicle associated membrane protein (AMP)-it interacts with two other proteins in the plasma membrane -syntaxin is a protein on the plasma membrane -snap25 is also a protein on the membrane -there are also v-gated channels on the plasma membrane -there is also synaptagmen: a calcium binding proteintriggers calcium binding to synaptagmin triggers neurotransmitters release -the binding of calcium to synaptagmin tells the proteins to wind together and connect to the plasma membrane -which causes it to smoosh together into a pathway in between the AMP to the plasma membrane-the pattern is the same when you’re trying to fuse a vesicle from the ER to the golgi or from the golgi out to another stack -whenever you think of the term conductile think v-gated sodium and v-gated potassiumchannels which are responsible for initiation and propagation—only in the conductile regions -the ones we are talking about are the ones that are at the trigger zone **there are no v-gated channels in the input region -what we have in that membrane are 1000 synapsePropagation of a decrementing potential -the potential that we created is positive charge like the “leaky garden hose” -the amplitude of the potential is going to get smaller as it goes down the neuron -it is important because we are trying to deliver positive charge EPSPS summate to provide sufficient positive charge to reach threshold -so that all the different input regions provide positive charge to make this happen -this is called synaptic summation (spatial
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