**Glial Cells**
The human brain contains 86B neurons and 85B Glia.

**Different types of Glia:**

🔸 Astrocytes: Astrocytes are really important type of Glia. They're essentially responsible for keeping the environment clean, they're the sanitation worker of the brain. So they are picking up all the refuse that the neurons have let loose including excess ions, excess #neurotransmitters and their metabolites.

They also are very important during development. They allow neurons to get to where they have to go during development. #Neurons are born in one place and they have to go some place else, and what highway did they take? They hitch on a progenitor cell that is going to become an #Astrocyte.

And, in addition when synapses are formed, the synapses are not maintained without some effort, and part of that is that the synapses are enveloped in the processes of #Astrocytes. So, there's a lot of structural and metabolic support that the Astrocytes are providing for neurons.

🔸 Oligodendrocytes and Schwann Cells: The #oligodendrocytes make myelin in the CNS and the #SchwannCells make it in the Peripheral Nervous System. So all these demyelinating diseases will affect either central myelin or peripheral #myelin. They will not affect both -- central or peripheral.

Because they are made by two different types. The Oligodendrocytes in the central nervous system and a Schwann cells in the peripheral nervous system.

🔸 Microglia: #Microglia are the one exception to the rule that
nervous system, that the cells of the nervous system come from Ectoderm. These are actually essentially immune cells coming from the blood lineage. These are immune cells that have invaded into the central nervous system and their job is to be quiet. And if we're healthy and everything goes well, they are quiet. But when there is a problem these microglia react, they try to rectify things, they try and bring some attention to areas of damage and what is emerging is that sometimes they go overboard and they start to participate in making the problem as well as solving the problem.