Neurofibrillary tangles are deposition of
**Core Concept**
Neurofibrillary tangles (NFTs) are a hallmark pathological feature of neurodegenerative disorders, particularly Alzheimer's disease. They are composed of hyperphosphorylated tau protein, which aggregates and forms insoluble fibrils that accumulate within neurons, disrupting normal neuronal function.
**Why the Correct Answer is Right**
The deposition of neurofibrillary tangles is a result of the abnormal hyperphosphorylation of tau protein, leading to its aggregation and formation of insoluble fibrils. This process is mediated by various kinases, including glycogen synthase kinase-3 beta (GSK-3β) and cyclin-dependent kinase 5 (CDK5). The accumulation of NFTs in neurons is associated with neuronal dysfunction, apoptosis, and ultimately, neuronal death.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the composition of neurofibrillary tangles.
**Option B:** While amyloid beta plaques are another hallmark of Alzheimer's disease, they are distinct from neurofibrillary tangles in terms of composition and location.
**Option C:** Neurofilaments are a different type of protein that forms intermediate filaments in neurons, but they are not the primary component of neurofibrillary tangles.
**Clinical Pearl / High-Yield Fact**
Neurofibrillary tangles are a key diagnostic feature of Alzheimer's disease, and their presence can be used to support a diagnosis of this condition. However, it's essential to note that NFTs can also be found in other neurodegenerative disorders, such as frontotemporal dementia.
**Correct Answer:** D.