NETTER - Neuroscience Flash Cards

Synaptic Morphology
1. Dendrite
2. Axon hillock
3. Initial segment
4. Nodes of Ranvier
5. Axon
6. Myelin sheath
7. Afferent axon ending on dendrite
8. Neurofilaments
9. Neurotubules
10. Axon (axoplasm)
11. Mitochondria
12. Glial process (astrocyte)
13. Synaptic vesicles
14. Synaptic cleft
Comment: The distribution of incoming synapses on a target
neuron determines the source and excitability of that neuron. Some
extensive synapses (serial) or synapses near the initial segment of
the axons exert a disproportional influence on the eventual firing of
action potentials by the target neuron. In general, synaptic vesicles
fuse with the axonal membrane at the synaptic cleft upon neuronal
depolarization and the accompanying influx of calcium, triggering
the simultaneous release of many quanta (vesicular content) of
neurotransmitter. An axon terminal may release more than one
neurotransmitter, depending upon the frequency of axonal firing and
the local and distant influences (e.g., induction) on gene expression
in the cell of origin. Neurotransmitter release is not necessarily
linear with frequency of firing. Also, in the CNS, there is often a
mismatch between sites at which neurotransmitter is released and
the presence of cognate receptors for that neurotransmitter on
potential target neurons. These factors collectively contribute to the
complexity of synaptic signaling in the brain.
Overview of the Nervous System See book 1.10