Alzheimers disease brain cell Coloured transmission electron micrograph TEM of a neurofibrillary tangle in a nerve cell from the brain of a patient with Alzheimers disease The tangle red lies in the cytoplasm yellow of the cell body adjacent to the nucleus green It consists of abnormal aggregates of the protein tau which in the healthy cell stabilises microtubules in the cytoplasm It is not known precisely how the tangles are formed nor their impact on the neurons function but they are seen in a range of neural disorders including Alzheimers disease CreutzfeldJakob disease CJD some forms of Parkinsons disease and Supranuclear Palsy