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Motor Neuron. The red line outlines a portion of a motor neuron located in the ventral horn of the spinal cord (left imagte). Note the large lightly-staining nucleus (red arrow) and a prominent nucleolus. This type of a nucleus is very characteristic of neurons. One dendrite is shown containing Nissl bodies (yellow arrows). The black arrows are pointing to nuclei of neuroglia cells. Note the size difference tweeen the nuclei of the neuron and the neuroglia.

The image on the right is a higher magnification of the motor neuron illustrating Nissl bodies scattered within the cytoplasm. Nissl bodies represent accumulations of free ribosomes and rough endoplasmic reticulum and therefore stains basophilic. These structures are found in perikarya and dendrites but not in axons.