Has your brain ever wondered what the parts of brain are?

 Brain consists of five divisions.

First, the myelencephalon, or medulla, and the metencephalon, consisting of the pons, and the cerebellum. These first two regions comprise the hindbrain. Next, there is the mesencephalon, or midbrain. 
The diencephalon, comprised of the thalamus and hypothalamus, as well as the telencephalon, which together comprise the forebrain. The telencephalon is the largest part of the brain and the most familiar looking, with its two cerebral hemispheres covered by the cerebral cortex. 

Stacked on top like another scoop of ice cream is the limbic system, or the so-called rat brain. And all the way on top is the cortex, or monkey brain, since this region evolved most recently once primates came onto the scene. Zooming in further, inside all of these regions, there are specialized cells called neurons. Basic knowledge regarding neuronal structure and the generation of the action potential that is used to relay signals through the body. 

In addition to the neurons of various types, their are neuroglia, also called glial cells, or simply glia. These are the other cells present in nervous tissue that are not neurons. 

In the brain, the first of these are called oligodendrocytes, which form myelin sheaths that wrap around one or more axons to protect them, and which speed up conduction along the axon, just like Schwann cells do in the peripheral nervous system. 

Next are astrocytes. These are heavily branched cells that attach to neurons, supporting them, and also anchoring them to nutrient supply lines. They absorb and secrete various substances, thus allowing them to perform a variety of functions. Then, microglial cells. These have long processes that monitor the health of the neurons, and can perform phagocytosis to get rid of dead ones. 

And lastly, ependymal cells. These are the cells, typically ciliated, that line the central cavities of the brain and spinal cord, forming a barrier between the cerebrospinal fluid and the fluid surrounding the cells of the central nervous system. This cerebrospinal fluid cushions the brain and protects it from physical trauma. 

Speaking of protecting the brain, we must also mention something called the blood-brain barrier. The circulatory system, throughout the body, substances readily diffuse through the walls of blood vessels so as to service tissues with nutrients and collect waste. Between hormones, ions, and many other things, lots of exchange is taking place. 

In the brain, many such substances would interfere with the ability of neurons to fire properly, so blood vessel walls within the brain are not as permeable. Most large molecules, like proteins and many drugs, are not able to get through, while molecules that are critical to the survival of neuronal cells, like oxygen and glucose, can make it, as well as psychiatric drugs. The endothelial cells in these blood vessel walls form tight junctions, which are what restrict the permeability. This blood brain barrier is critical in preventing certain substances from entering brain tissue that would interfere with the firing of neurons.