 Hello, my little dog, Pounds of a Feather. So today in the last lecture we talked about the endocrine system and we looked at how the endocrine system can function as an integrator. And it does so with chemical messages that are dumped into the blood that act on distant targets. And those chemical messages are hormones. So today we're going to start looking at the nervous system and how the nervous system can act as an integrator. And the very first thing we need to deal with is the fact, remind ourselves that the first half of the nervous system's wet mechanism for communication involves the action potential. So the entire lecture today is to prep us for dealing with the action potential. You know that the action potential is an electrical signal that ultimately results in a chemical signal being released upon an effector and that happens at the synapse and we'll deal with that aspect of neural communication in the next lecture. So remind yourself, probably when you think of the nervous system you think of neurons. And if you've taken anatomy then you know that, you know what? Neurons aren't the only player in the show and in fact a dead white guy named Camillo Golgi, fantastic. Information found on the internet about Camillo, when he was born, fantastic. When he won his Nobel Prize, probably for, I mean this guy, his name is Golgi Dog Pound, so you can guess that a bunch of his research dealt with the Golgi apparatus. Apparently back in the day he dropped a brain into silver nitrate and it stained all crazy colors and he realized that neurons were only 10% of brain tissue and the other 90% was made up of these glial cells. So he's kind of famous, I think it's fascinating and very important that they tell us that he was white. And thank goodness, also straight. Seriously, these things kill me and it really is out there. Like this is important that we know these things. We do know that back in the day it was rather challenging for people of multiple colors of skin and people without penises to get involved in the studies of science and we know that now that barrier is definitely being broken down, which is really good. I always find these things entertaining. So let's go see what Camillo actually discovered and if you have had anatomy then you know that, dude, we discovered we have multiple kinds of cells in the nervous system and this one right here, this big yellow one, is that yellow? That's the neuron and in the next section we're going to draw a picture of it. We also have these little like immune cells and microglia. These are actually macrophages that are found in the cell. We have these guys that look like they're holding on to the axon of the neuron and we're going to do neural anatomy in a second, but these guys are called oligodendrocytes. Oligodendrocytes. And the oligodendrocytes make myelin sheaths surrounding neuron axons and we'll look at those guys in a second. So we have these guys here. These are your astrocytes. Astrocytes play a role in the blood-brain barrier. You can see that the astrocyte has hands touching the neurons so they're helping kind of clean the neurons and there's evidence that they actually play a role in mediating communication between the neurons, deciding like what is a viable message and what isn't. But then you can see they also have their hands on the capillaries in the brain and this creates this blood-brain barrier where you have the capillary layer, the epithelium of the capillary and then you have this other layer from the astrocytes and that produces two layers of thickness more double what you would normally have to pass through if you were something that wanted to exit the capillaries in the rest of your body. But in the brain you've got twice as much to get through and then of course you've got these little guys. Don't they look like some sort of epithelial cell? These are your ependymal cells and the ependymal cells have cilia and they produce cerebrospinal fluid and they help circulate that cerebrospinal fluid throughout your nervous system. So 90% of your cells are all these other ones and only 10% are neurons. All these other cells are very important for neural function but the action potential itself, we're going to look at that. First of all we're going to look at the neurons anatomy and then we're going to look at how the neuron communicates electrically. Be right back.