Structure of a Chemical Synapse

The synaptic knob (fig. 12.17) was described in chapter 11. It contains synaptic vesicles, many of which are "docked" at release sites on the plasma membrane, ready to release their neurotransmitter on demand. A reserve pool of synaptic vesicles is located a little farther away from the membrane, clustered near the release sites and tethered to the cytoskeleton by protein microfilaments.

The postsynaptic neuron does not show such conspicuous specializations. At this end, the neuron has no synaptic vesicles and cannot release neurotransmitters. Its membrane does, however, contain proteins that function as receptors and ligand-regulated ion gates.

Neuronal Synpatic Vesicle Release

Figure 12.16 Synaptic Knobs on the Soma of a Neuron in a Marine Slug, Aplysia (SEM).

Are these synapses axodendritic, axosomatic, or axoaxonic?

Saladin: Anatomy & I 12. Nervous Tissue I Text I I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

464 Part Three Integration and Control

464 Part Three Integration and Control

Microfilaments Neurons Images
Figure 12.17 Structure of a Chemical Synapse.

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