CSB332H1 Chapter Notes - Chapter 12: Cytosol, C-Terminus, Choline Acetyltransferase
23 Mar 2013
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Axon terminal depolarization and release. Chapter 13 243- 248; 250- 252; 255- 256. Chapter 13 release of neurotransmitters. Stimulus to release nt is the depolarization of nerve terminal. Release occurs as result of calcium into terminal through voltage- activated calcium channels. Transmitter secreted in multimolecular packets (quanta) each containing several thousand transmitter molecules. In response to ap, 1- 300 quanta are released almost synchronously from nerve terminal depending on type of synapse. At rest, nerve terminals release quanta spontaneously at slow rate giving rise to spontaneous miniature synaptic potentials. Also, there is continuous, nonquantal leak of transmitter from nerve terminals. One quantum of transmitter corresponds to contents of one synaptic vesicles and comprises of several thousand molecules of low- molecular- weight transmitter. Components of vesicles are retrieved by endocytosis, sorted in endosomes and recycled into new synaptic vesicles. Stellate ganglion of squid used to determine precise relation btw presynaptic membrane depolarization and amount of transmitter release.
