The most plentiful proteins in the axon are the proteins forming the microtubules, neurofilaments and actin filaments ( microfilaments). Proteins and other substances must be provided by the synthetic apparatus in the cell body and transported along the axon.
Metabolic activity (biosynthesis) in axons is limited (there are no ribosomes, endoplasmic reticulum, golgi body). Most of the projecting neurons send axon collaterals into the local neuronal circuits, some of the neurons of local circuits send axons collateral toward more distant structures – no distinct functional difference between the two classes of neurons. It passes into initial segment, which differs from the next part of axon in the special functional properties of its membrane (low threshold – high excitability due to densely packed Na +-VGCs). The axon arises from the soma (or sometimes from a dendrite) in a specialized region called the axon hillock. Interneurons (neurons of the local circuits) – short axons with side branches in the vicinity of the cell body (up to several mm) usually smaller cell bodies, lower amount of cytoplasm, less organelles.Projecting neurons – long axon with terminal branching (several mm in length up to about 1 m) usually larger cell bodies + numerous cytoplasmic organelles.They have a high variability of branching pattern and extent (characteristic for individual neuronal types): The axon is the long projection of a nerve that can reach a length of tenths of centimeters, that conveys electrical impulses from the dendrites/soma of the neuron to the next neuron.
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