Neurofibril
A neurofibril is a fibril (a small or slender nerve fiber or microtubule) that is found in the cytoplasm of a nerve cell and causes excitation. It can refer to groups of small, microscopic fibrils that extend to the dendrites, axons, and sometimes the synapses. Visible only through the use of light microscopy their functional significance remains to be fully established or understood. Neurofibril can also be used as an antiquated term to refer to fibrous neurofilament bundles in neurons when observed through microscopic stained tissue sections.