Anatomy and Cell Biology 4451F/G Lecture Notes - Lecture 9: Cytoskeleton, Piccolo, Second Messenger System
5 Oct 2017
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Presynaptic terminal (end of axon), normally have more than one presynaptic terminal. Many axon terminals that form presynaptic side. Sometimes synapses that make synapses on presynaptic terminal influence output of the pre synaptic axon it acts on vs the entire neuron. When ap propagates actively down axon, it opens vg ca+ channels, Ca rushes in and that causes vesicles fuse w pre synaptic membrane thereby spilling out nt, diffuses through cleft, binds to nt receptors (ionotropic or metabotropic) Cl can rush in and cause hyperpolarization or shun depolarization (without entering or exiting cell) Other s(cid:455)(cid:374)apses that do(cid:374)"t really form pre and post synaptic terminals these are varicosities. We also see varicosities in lower evolved animals (insects) varicosities might be older form of synaptic transmission varicosities can lie adjacent to post synaptic structures where nt receptors are located. Here alpha 7 nicotinic receptors located in muscle, here varicosities work like terminals release nt in synaptic cleft which binds to receptors.
