 Hi everybody, Dr. O here. So now that we've learned the general senses, it's time to jump in and look at the special senses. So really quickly, special senses are the senses that have specialized sense organs that send information to specialized parts of the brain. So that's what makes them different than your general senses like pain. The five special senses we're going to cover are going to be olfaction or smelling, gustation or tasting, vision or seeing, equilibrium, which is balance and then hearing. So in this video, we're going to go ahead and dive right in and cover olfaction or your sense of smell. So let's get started. So here we see where olfaction occurs. So the olfactory organs, the olfactory epithelium and those specialized cells, the receptors, are in the nasal cavity on either side of the nasal septum there and we'll cover the anatomy of the nose later in the respiratory system. So the olfactory epithelium is going to be these specialized olfactory receptors and then whatever support cells are needed and then stem cells to replace them. So as we get older, these stem cells kind of lose their function and that's why our sense of smell starts to go away. One of the key things here though, and you'll see this better in the next image, I guess, is the surface of these olfactory organs have to be coated with secretions from olfactory glands like mucus. So they can go ahead and see that here. So you see the olfactory receptors, they're a very specialized type of modified neuron, but they only work if the chemicals that they're sensing are dissolved. So your olfactory receptors, they look for odorant binding proteins, but they need to be dissolved in that mucus first, which is why you can't smell very well or much at all if your nose is really dry. So just like with taste, these chemoreceptors, the reception only happens if these compounds are dissolved in some sort of liquid. All right. So the actual pathways. So now the olfactory receptors, they've picked up a signal that's been dissolved in mucus and now we're going to go ahead and send that signal to the brain. So the axons of these olfactory epithelium are going to form these 20 or so bundles that are going to travel up through the cribiform plate of the ethmoid bone there and reach the olfactory bulb, which is sitting right below the frontal lobe of the brain. That's where that first synapse occurs, then the signal is going to be sent back to your temporal lobe is where we're going to end up. So the olfactory bulb is going to be connected to the olfactory tract. This is now our cranial nerve one, our olfactory nerve. But a couple of cool things to note here. Smell is a very special sense, right? We as humans are very visual creatures, but our brains are built on these animal brains that most animals are dominated by the sense of smell. So yes, the information that's traveling down cranial nerve one is going to reach the temporal lobe, the olfactory cortex. But some of this information is also going to reach your hypothalamus, which controls homeostasis and then some of this information is going to also reach the limbic system. And this is why your sense of smell can trigger profound emotional and behavioral responses as well as memory. I would say that smell is linked to emotion and behavior and memories in ways that no other sense is. So smell is still a very, very powerful sense in humans, even though we would say that we're very visual creatures. Another important thing to note here olfactory stimulation or olfaction or smelling is the only sense we have that is not filtered by the thalamus. So your olfactory nerves do not stop at the thalamus where information can be filtered out. The information goes straight to your cerebrum and your conscious mind. So if that's true, then why do we lose the smell of something? Like you smell a new cologne or you smell something really bad and you smell it and then it goes away. Well, it's not really the receptors. So olfactory receptors don't really adapt much at all. So this would be called central adaptation. When you get used to a smell it's because your brain just kind of quit paying attention to it. Okay, I think that's everything you need to know about the sense of smell or olfaction. I hope this helps. Have a wonderful day. Be blessed.