Neurofibrils are found in the cytoplasm of the cell body, axon, and dendrites. They consist of a network of neurofilaments and microtubules. Neurofibrillary tangles (NFTs) form inside the neuron when a microtubule associated protein, known as tau, aggregates into insoluble paired helical filaments. It is believed that when NFTs form inside the cell, it causes the neuron to become stressed and eventually die. The presence of NFTs in nervous tissues is recognized as a primary marker of Alzheimer's disease.
