Alzheimer's disease - plaques, tangles, causes, symptoms & pathology

Dementia isn’t technically a disease, but more of a way to describe a set of symptoms

like poor memory and difficulty learning new information, which can make it really hard

to function independently.

Usually dementia’s caused by some sort of damage to the cells in the brain, which can

be from a variety of diseases.

Alzheimer’s disease, now referred to as Alzheimer disease, is the most common cause

of dementia.

Alzheimer disease is considered a neurodegenerative disease, meaning it causes the degeneration,

or loss, of neurons in the brain, particularly in the cortex.

This, as you might expect, leads to the symptoms characteristic of dementia.

Although the cause of Alzheimer disease isn’t completely understood, two major players that

are often cited in its progression are plaques and tangles.

Alright, so here we’ve got the cell membrane of a neuron in the brain.

In the membrane, you’ve got this molecule called amyloid precursor protein, or APP,

one end of this guy’s in the cell, and the other end’s outside the cell.

It’s thought that this guy helps the neuron grow and repair itself after an injury.

Since APP’s a protein, just like other proteins, it gets used and over time it gets broken

down and recycled.

Normally, it gets chopped up by an enzyme called alpha secretase and it’s buddy, gamma

secretase.

This chopped up peptide is soluble and goes away, and everything’s all good.

If another enzyme, beta secretase, teams up with gamma secretase, then we’ve got a problem,