so in this video we're gonna focus on the neuroglia if you'll never go back to the astons each Apter we talked about how nervous tissue had two major cell types within it we had neuroglia and neurons now the neuroglia we also called glial cells and these are not these are cells that outnumber neurons about ten to one they're smaller and they surround and wrap delicate neurons and some are involved with immune defense and a variety of interesting functions we'll talk about in this lecture now in further lectures we'll go into more detail on neurons or nerve cells and these differ from neuroglia because they're the excitable cells that transmit electrical signals that can basically be involved with high-speed communication on the body so in terms of the types of neuroglia cells we have four major types here we have astrocytes microglia ependymal cells and oligodendrocytes but these are the ones that you find in the central nervous system turns out we actually have a separate set of glial cells in the peripheral nervous system and the reason being is just that these two divisions of your nervous system develop in different ways so you find that those different cell types between them now the astrocytes are the most abundant and they're called astrocytes Astro means star cell site is cell so they're kind of a star-shaped cell they're versatile highly branched hence the star appearance and they cling to neurons and synaptic endings as well as capillaries now by being a highly branched they can actually help us support and brace neurons they play a role in exchanging materials between capillaries and neurons and therefore part of what we call the blood-brain barrier astrocytes early on in neural development help guide the migration of young neurons by sending out little scaffolding rods of protein that essentially neurons can can walk along and astrocytes also control the chemical environment around neurons ensuring that the problem proper chemical environment exists so that neurons can transmit action potentials they can respond to nerve impulses and neurotransmitters the influenced neuronal functioning and astrocytes can participate in information processing within the brain so it turns out these last three are kind of a more recent discovery about astrocytes but it seems that they actually play a role in the communication as well now in terms of what they look like member these things are abundant in highly branched so you can see here is the cell body and all these extensions that stick off you can see a lot of these extensions actually wrap around blood vessels and this is important because astrocytes are involved what we call the blood-brain barrier because they basically prevent harmful substances in your blood from making it in your brain tissue neurons also help to transmit nutrients tuner I'm sorry astrocytes also help to transmit nutrients to neurons and these nutrients then are actually able to be absorbed by those neurons and utilized but astrocytes also play a pretty key role in maintaining and monitoring the extracellular environment here so we find then is that the fluid environment within our brain is actually maintained monitored by our astrocytes so that if one ion gets in excess like potassium you know astrocytes can actually help to remove that and get those potassium levels back to a normal concentration within our brains tissue fluid now what's not shown here but what should be present is also the fact that astrocytes monitor synapses and they play a role in communication because the synapse is a point of communication between a neuron another cell but astrocytes actually play a role with monitoring those synapses and communicating now microglial cells are the small ovoid cells with thorny processes that touch and monitor neurons these can migrate towards injured neurons and can transform into an activated form which phagocytosed microorganisms and neuronal debris so think of the microbial cells is like the immune cells of your brain they're Fager sites because they can remove infectious organisms as well as dead material in fact for someone who has a stroke or a part of their brain dies that dead nervous tissue is basically reabsorbed by these microglial cells because they fake a site toast it and what you're left with is basically just a space that's fluid-filled where there used to be brain tissue now the microbial cells you can see these kind of thorny like cells here and normally they exist in the brain in their inactive form so that they're just there but they're activated by chemicals as well as exposure to foreign microorganisms and once activated these microbial cells help to mount an immune response by initiating inflammation but also in a large phagocyte which can engulf and remove debris from the brain now the ependymal cells can range in shape from either squamous to column Mar and these may or may not be ciliated but these are penile cells with cilia can beat to circulate the cerebrospinal fluid on the brain and they line the central cavities of our brain and spinal cord now penile cells form a permeable barrier between cerebrospinal fluid and the cavities in our brain called the ventricles and the function of serum spinal fluid is not keep your brain buoyant and nourish the brain from the inside so these ependymal cells play a very important role with helping to circulate this fluid that nourishes and protects our brain so what do these look like well they kind of line up like an epithelium and they line the the fluid-filled cavities deep within our brain so they almost look like a simple cuboidal epithelium and what these cells do is essentially take some of the substances you'd find in the fluid near your blood vessels and then transport those substances across their walls in order to make this new fluid called cerebral spinal fluid and they can circulate that fluid by the cilia that they have that can all wave and beat in a very specific and coordinated manner to help circulate this fluid around the inside of your brain spaces but also outside of your brain now the oligodendrocytes are these large bright cells that process and wrap central nervous system nerve fibers they can form this insulating myelin sheath that's thicker than nerve fibres and their purpose here is to actually help speed up the electrical impulses that are created by your neurons so they form this myelin which is this external wrapping and sheath and it looks a lot like the insulation around a wire well these these yellow wires here orange would essentially be the processes from our nerve cells that would conduct electrical currents so these myelin sheaths serve as like an insulator for the wires of our brain so in the peripheral nervous system we have two major neuroglia we have satellite cells and schwann cells also called neural mo sites now the satellite cells surrounding neurons cell bodies in the peripheral nervous system and their function is very similar to the astrocytes of your central nervous system in the sense that they help to basically protect and monitor the environment around those neurons now Schwann cells are functionally very similar to oligodendrocytes and they're also called neural limo sites but they basically surround peripheral nerve fibers and formed a myelin sheath or insulation in thicker nerve endings and these are more vital to regeneration of damaged peripheral nerves because the neural mo sites can help guide the severed axons of your neurons to reconnect if you have nerve injury so the satellite cells surround the cell bodies of peripheral neurons and remember the Schwann cells or neural mo sites form the myelin sheath or the insulation around the axons of your neurons in the peripheral nervous system