Cell Body

The cell body of a neuron has characteristics of a protein-producing cell

The cell body, or perikaryon, is the dilated region of the neuron that contains a large, euchromatic nucleus with a prominent nucleolus and surrounding perinuclear cytoplasm. The perinuclear cytoplasm reveals abundant rough endoplasmic reticulum (rER) and free ribosomes when observed with the transmission electron microscope (TEM), a feature consistent with its protein synthetic activity. In the light microscope the ribosomal content appears as small bodies, called Nissl bodies, that stain intensely with basic dyes and metachromatically with thionine dyes (Fig. 11.4). Each Nissl body corresponds to a stack of rER. The perinuclear cytoplasm also contains numerous mitochondria, a large perinuclear Golgi apparatus, lysosomes, microtubules, neurofilaments (intermediate filaments), transport vesicles, and inclusions (Fig. 11.5). Nissl bodies, free ribo-somes, and, occasionally, the Golgi apparatus extend into the dendrites but not into the axon. This area of the cell body, called the axon hillock, is free of large cytoplasmic organelles and serves as a landmark to distinguish between axons and dendrites in both light microscope and TEM preparations.

The euchromatic nucleus, large nucleolus, prominent Golgi apparatus, and Nissl substance indicate the high

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