Anatomy and Cell Biology 4451F/G Lecture Notes - Lecture 9: Autonomic Nervous System, Clathrin, Vesicle Fusion

• School: Western University
• Department: Anatomy and Cell Biology
• Course: Anatomy and Cell Biology 4451F/G
• Professor: All

Document Summary

There are other types of synapses that do not really form presynaptic and post synaptic terminals. These are thickenings of axons that contain the machinery of presynaptic terminals (neurotransmitter vesicles that can be released at varicosities but they are not axon terminals). This form of synapse we see a lot in autonomic nervous system that innervates gut and glands. Instead of one synaptic terminal innervating one muscle fiber, we have varicosities that uniformly release neurotransmitter over muscle cells. We also see a lot of varicosities in lower evolved animals (ex. insects). The varicosities may be an older form of synaptic transmission. These varicosities can lie adjacent to post synaptic structures where receptors are located. For example, alpha7 receptor is located very close to one of the varicosities. The varicosities work pretty much like axon terminals. They release nt into synaptic cleft that then binds receptors. In many cases, v are not directly opposite to post synaptic structures.