system
Given the following post, respond as if you're commenting on Reddit:
human
Do Cells That Make Up The Brain Get Replaced?

Skin cells die and get replaced with new ones continuously. Does a similar process happen for cells that make up the human brain?
gpt
The classic answer is no: once you're an adult, the neurons you have are there and you're pretty much stuck with them. The connections between them are constantly changing, though, which is essentially how memory and learning takes place (obviously a very simplified picture).

However, that picture has been complicated more recently. There's evidence that a few areas in the brain (part of the hippocampus and an area called the subventricular zone) can grow new neurons in adulthood. We're also starting to understand more and more the importance of glial cells, which make up something like 90% of the cells in your nervous system. They do a bunch of things and there are many types, but generally they provide support, protection, and nutrients for the neurons...but we're finding out more and more that they're very important for creating and maintaining junctions between neurons and may play a key role in a bunch of diseases and psychiatric illnesses.