Sensory System

Hi. In this lesson, we'll be talking about the sensory system, which is the part of the nervous system that receives and processes sensory information. It's going to be our body's way of identifying what's out in the environment and going to give us the information necessary to construct our realities. So the first step of this is gonna be sensory reception, which is just the detection of some type of stimulus by sensory receptors. A sensory receptor is a type of nerve that responds to some stimuli and trans deuces. A response is either a graded or in action potential, and it should be noted that sensory receptors on lee respond to very specific stimuli for example, temperature within a certain range or ah, light of a very specific type. Now, sensory transducer, uh, ction is the conversion of that stimulus into some internal signal, like a graded or an action potential. So our sensory receptors air going to trans deuce the signals they get, and during transaction, these signals can actually be greatly amplified. Now the receptor potential is essentially a type of graded potential that's generated by the activation of sensory receptors, so thes grated potentials will either deep, polarized or hyper polarize theme membrane potential off these nerves. And that will either in lead to action potentials or in the case of hyper polarization, prevent action potentials and thes uh, you know, thes action potentials. It should be noted, are you know, acts potentials. Onley have It's like an all or nothing signal. They only have one signal that they can send. So the magnitude of these receptor potentials is going to be encoded in the frequency of action potentials that air issued and over time, sensory responses to a stimulus can change and we actually call that sensory adaptation. Now, here you can see a bunch of different types off sensory receptors and, uh, you know, they come in ah, wide variety of shapes and sizes is really the end. Take away here on what I want to point out is behind me how, for example, a sensory receptor will either d polarized or hyper polarized. So in the case of the pressure receptors in our skin that we use thio sense, different types of touch light pressure will actually deform these nerves and physically pull open channels that allow ions through so light pressure will, uh, slightly open the ion channel and allow just a little bit of, in this case sodium through, whereas a big pressure will cause a great D formation and allow a large amount of sodium to enter the cell and result in a greater deep polarization. So not every type of sensory receptor is going to work by some type of physical de formation that opens ion channels. But I think this conveys nicely the, uh, you know, the different ways in which magnitudes can be conveyed by, you know, the literal opening of channels. I mean, that's how these things are working. So once the information has been transducer, it has to be transmitted or sent to the central nervous system, and sensory neurons will actually carry this information to specific parts of the brain because of localization of function. Uh, there are specific areas dedicated to processing sound dedicated to processing, uh, visual stimulation. In fact, amongst visual stimulation, there's different areas that process different types of visual stimulation, like edge detection or motion. Now this all sums together into what you would call perception, which is our brain's way of taking the sensory information processing it and turning it into a meaningful representation of stimulus. So you know, the way you know we often think about the world is you know, I'm seeing the world around me when in actuality, that's not what's happening. What's happening is light is hitting the sensory receptors in your eyes and conveys various signals to them. And then that information is taken to the optic cortex, right, the or the visual cortex, and there it's processed, and then what you see as the world around you develops during that process. So, really, everything that you perceive as your reality is the world around you is more or less in your imagination when you really think about it, because it's just a construct in your mind and what you're perceiving is the world around. You could, in fact, be very different from what someone else perceives is the world around them. You know, one of the greatest examples that you can really give of this is that when we see images, we're actually seeing them upside down the way that light enters our eye and stimulates our sensory receptors. There. We actually end up with an image that's the upside down version of what's out in the world. Our brain is actually what takes that and flips it right side up. Just a nice illustration of how our minds air actually constructing what we consider our realities. Now with that, let's go ahead and flip the page light stuff, right?

There are many different types of sensory receptors, so let's go through some of the categories. Mechanic receptors or mechanical receptors are like physical receptors. They will respond thio physical stimuli like pressure and physical distortion. So if I smash my finger the sensory receptors that air picking up that information and sending it to my brain, our mechanic receptors now thermal receptors respond to changes in temperature. They are temperature receptors if you want to think of them that way. Appropriate scepters. Kind of a weird group of sensory receptors. They actually respond to position and physical movement in the skeletal muscles and joints, and they're gonna play a role in helping to maintain balance and body posture. No susceptible, sometimes called pain receptors, respond to tissue damage and will potentially lead to pain perception, but not necessarily now, chemo receptors respond to various chemical stimuli, and this can come in a wide variety of forms, from the chemo receptors in our nose, responsible for our sense of smell to receptors. That sense Kapsis in which is the you know, chemical in hot peppers that gives you that burning sensation. Now photo receptors will actually respond. Thio light or photons, hence their name. And you can see two examples of photo receptors behind me. These air the photo receptors found in our eyes, rods and cones. And we'll talk more about these in just a little bit. And over here you can see some electro receptors in these fish these air receptors that respond to electric field. So you can see here that, uh, the organisms use this to pick up on other organisms in their area because our bodies are electrically conductive. So here this organism is going to sense the distortion in the electric field due to this other creature and therefore sense its presence. Whereas an object like a rock, for example, uh, isn't going, uh, to conduct that. And so it's, you know, not going to be alerted like it would if it picked up another organism in its area. And there's also magneto receptors, which, you know, like electro receptors, respond to electric fields. These magneto receptors respond to magnetic fields. Now let's actually go ahead and flip the page and take a look at a specific type of sensory receptor

hair cells or sensory receptors used by the auditory and vestibular systems. And they'll actually respond to physical stimulation, which will result in the opening of ion channels. So surprising as it might sound the sensory receptors responsible for your perception of sound, you know your ability to here are actually responding to physical stimulation. Now the reason they're called hair cells is because they have these hair like projections called stereo cilia that come off of the hair cells and are actually what will be physically manipulated in order to open those ion channels, which will result in a change in membrane potential. Now, when thes stereo cilia are bent, there's actually ion channels located near their base that get pulled open due to the bending. So here, picture a stereo. Cilia like this, and if it gets bent over, this is actually going to pull open this Iron Channel and allow some ions to go through. Now, if we really heavily pull open our stereo cilia drawing three arrows, Thio sort of represent strong force, pulling it that way that's actually going to lead to Maura Ions. Getting through It's going to cause a greater deep polarization, so the actual bending will. The grading of the bending will result in the grading of the potential in the membrane. Now, a cool way in which these hair cells air used is actually in something called a status ist. And this is like a balanced sensory receptor that, uh, for example, marine invertebrates used in order to get a sense of gravity. I mean, you know, the oceans kind of hard to tell up and down without gravity, so this is a way for them to sense gravity. So this status ist, um, has this sac like structure that you see here, and it's gonna be surrounded by hair cells. See all of these dudes in here hair cells and you can see they have all these little projections coming off of them. Those air, their stereo still stereo cilia. Now, inside this sack of hair cells is what's called Statoil with or stata lifts these air crystals that will touch the hair cells to stimulate them. So you can see here we have our stat, Elif, and this status life is going to sink due to gravity. And wherever it touches the hair cells, that's going to cause, uh, stimulation that's going to be transducer in that signal will be sent and allow the organism to know. Okay, that weighs down. That's where the gravity's pulling status with in my status ist of course, the you know, these organisms don't even know they have status ists. But you get the idea now, another cool way that organisms use hair cells is in what's called the lateral line system. This is something that, uh, some fish have and also amphibians that allow them to detect movements in water. And you can see here the lateral line system has this canal that lets water in, and there are hair cells located in here. You can see a zoomed in version here, and actually these hair cells will have basically a big dome over it known as a coupla. You really need to worry about that. The point is, water moving through these channels can lead to the stimulation of these hair cells, and this will result in these organisms being able to tell where the water is moving around them and therefore have some idea of where you know an organism, for example, is relative to them. With that, let's actually go ahead and flip the page

hearing is the perception that results from our ears, transducer and sound sound is a type of vibration that propagates as pressure waves moving through air or water. Now waves have what's known as frequency. This is thesis Eichel's per second of a wave. Here you can see a model of a wave and one cycle would be one complete revolution if you want to think of that of the wave. So if we start at this point on the wave and go all the way until we get to that same point again, that is one full cycle Now, Technically, I should point out that this wave we're looking at here is a different type of wave from a pressure wave. A pressure wave is a longitudinal wave. This is a trance first wave. That's just for the physics people out there for our purposes. It doesn't really matter, because this is actually much easier visual representation than what a pressure wave looks like. So just know that one cycle is essentially one revolution of the wave. If you want to think of it that way and that perception of frequency, which is the number of cycles per second comes in his pitch. That's basically like the notes of music. You hear right, the different types of sound, the different, uh, you know, um, scales of sound that you hear That's just our perception of frequency now, the amplitude of these waves, which you can see here, this amplitude that is what we hear as volume. So the higher the amplitude of the wave, the louder we perceive the sound to be. And our ear is the Oregon that will take in this sound and turn it into something meaningful for our brains. So how does that happened? Well, the year actually has three different parts to it. The outer, middle and inner ear. The outer ear is basically just, you know, the cup that sits on the side of our head that is shaped to best gather sound and filter it into this tube. Now this tube will end at what's called the Tim Panic Membrane. This is the ear drum. It's a thin membrane that separates the outer ear from the inner ear and is going thio essentially represent the first step of sound being, uh carried into the body and turned into a meaningful signals so in the middle ear. We have these bones, and these bones were gonna be responsible for amplifying sounds that come from the environment. These bones air called obstacles, and there's actually three of them, and you can see them. Here we have 12 and three, and these obstacles will move based on sound waves hitting the Tim panic membrane, causing them to move. And basically they're gonna act like a kick pedal on a drum almost and hammer against this structure. The oval window. Now the oval window is a membrane covered opening that leads from the middle ear to the inner ear. So we have these two membrane membrane covered openings, one that you know hits the Ahsoka Lisey's and then the one that the obstacles pound on to essentially transmit sound. Now the obstacle that's actually hitting on the oval window is called Stay peas, and I also want to briefly mention do you station tube. That's actually what connects your middle ear to your nose and throat region, the nasal pharynx and whenever. If you've ever flown on a plane or had your ears plugged up before, that's from your you station tubes. That's from pressure in pressure changes in the station tubes, causing that sensation. So let's actually go ahead and flip the page and move on into the inner ear.

the inner ear is the portion that actually contains the sensory receptors that are responsible for detection of sound, and they're going to be involved in balance. Now. The balance detecting system is called the vestibular system, and it's basically attached to the sound detecting system. The vestibular system is made up of these semi circular canals, these three fluid filled cavities that you can see here on the inner ear structure and essentially fluid is going to move through these canals and stimulate hair cells in them. And that's how we're going to be able to detect rotational motion and get a general sense of balance. This is why, for example, is a kid you know, when you spin around a lot, you get dizzy. It's because the fluid is still moving through your semi circular canals due to inertia. So you're still getting that perception that you're moving even though you've stopped. Now the co KLIA. This structure is what's going to be responsible for the detection of sound, and it's a spiral shaped cavity, and it kind of looks like a cone that got coiled up. Now you can see a sort of a modified version of the cochlear here, which is made to look like what the co. Cleo would appear as if it were uncoiled. That's why it's all straightened out. However. In reality, it's, you know, structure is all curled up. So imagine taking this and then rolling it up like a fruit roll up or something. No, the CO CLIA has a bunch of different structures in it. You don't need to worry about all of this, but I'm just going to give you a general sense of what's going on in there so that we can talk about the part that you do need to understand. So the cochlea actually has three ducts in it, or three fluid filled tubes. There's this one on top we call the vestibular duct. There's the Tim panic duct on the bottom, and then in the middle we have the cochlear duct. Now the hair cells in the cochlea, that air going to be responsible for detecting sound, sit on something called the basilar membrane. This is the membrane kind of in the middle of the cochlea. That's gonna be underneath the cochlear duct and above this Tim panic duct. But really, you only need to know about the basilar membrane because that's what the organ of Corti sits on. This is the structure that contains many hair cells. As you can see, here we have our organ of Corti and all these little projections on the top are our hair cells. And, uh, this these air the hair cells that are gonna be stimulated to perceive sound. Now it's worth noting that the basilar membrane is different in different regions of the Coakley A it it will actually have different regions that vibrate at different frequencies of sound waves. And in this way, we're able to better perceive ah, wider range of sound frequencies. No, how these hair cells in the organ of Corti air actually stimulated has to do in part with something called the Tech Torrey. Um, membrane, this is gonna be a little membrane. Could see it here that sits above our hair cells, which are here in the organ of Corti. No, basically, when a when the stay peas hits the oval window, it's gonna send a wave through the fluid, um, of the coke Leah. And that fluid moving is going to vibrate those membranes. And those membranes are going to move when they vibrate, right? That's kind of what vibrating means, But that vibration is of the basilar membrane is going to cause those hair cells to bend due to their connection with the tech Torrey a membrane, although it's worth noting that not all hair cells are going to be connected to the tech Torrey a membrane and I should point out that this process is not super, super well understood. So, you know, in 10 years time or something, maybe what I'm saying well, no longer be held is through the standard of the day, so not totally well understood. But there is an interaction between those hair cells and the territorial membrane, and it's those hair cells being stimulated. That's going to lead to the perception of sound. And again, remember that the amplitude of the wave translates into volume, and the frequency of the vibrations translates into pitch. Now I also want to point out that there's the structure called the round window. That's kind of all the way. At the other end of the cochlea and its job, it's It's a membrane covered opening like the oval window, but its job is to dampen waves and prevent reverberation. Essentially, this is going to allow, uh, the waves to sort of defuse their energy out of the cochlea. And, uh, you know, make sure that they're not just reverberating or like echoing around inside there. So with that, let's actually go ahead and flip the page.

photo reception is the detection of light, and this is carried out by many different organisms from us. Humans with are very complex eyes to nematodes, you know, little round worms in the soil that have photo receptors that can detect the presence or absence of light. Now we're going to take a look at some more sophisticated systems that carry out photo reception. Namely, we're gonna look at eyes now. Insects and arthropods in general have an interesting I called the compound I This is an I composed of many little repeating units called a materia. And hopefully you can see here all thes little repeating units all over the I. I mean, I can't even begin to dot com all those air all, oh, material which are basically structures that contain clusters of photoreceptors. Here we have what you could think of as like a cross section of the compound I So if we cut a slice into our compound, I This stuff at the top represents the surface of the eye and these air all those subsurface structures and each one of these is an O materia. And if we go over here, you can see a zoomed in version of the O materia and it's going to contain a cluster of photo receptors. And that is how these eyes were going to detect light. Now, this simple I, which is just a single lens, I is what we have and this is going to operate similar to a camera with its single lens. Now, the human eye can Onley perceive light in what's called the visible spectrum, which is just a small portion of the electromagnetic Uh uh the spectrum of electromagnetic radiation, which you can see down here. In fact, this visible light is not even close to proportional with, uh, in this chart, the visible light is just a teeny little sliver on this huge range of different types of electromagnetic radiation. Now, looking at the I, the white of the eye is known as the school era, and this is basically a protective structure, and it's gonna be composed of in part collagen and elastic fibers to give it a tough, resilient structure that can, you know, take a little squishing in motion. Now the cornea is basically the fluid filled, transparent cover over the iris and the pupil. It's kind of hard to see in a head on image. But here you can see it as this area in here, above the lens right here. Now, the iris is the colored area around the pupil, the pupil being this dark center of the eye. The iris is this region that I'm just kind of scratching. And around here, that is our iris and the irises, not just there to make our eyes look pretty and give him some color. It's actually there to control pupil diameter and lens shape, which is going to be very important for focusing lights so that we can perceive a clear image. I mean, look at me. Clearly my eyes air. Incapable of that is I wear corrective lenses. I actually need a little assistance because my eyes can't quite focus the light properly. Now the pupil is that black hole, as I said, and it's going to be the thing that allows the light to pass through the lens. So if you look over here, this structure is our lens. And this opening here, that eyes on top of it, that is our pupil. It appears black because light is getting sucked in there and black is, of course, what we see when there is an absence of light. Now the lens is going to actually change its, uh shape in order to focus light from the cornea. However, the cornea itself has some strong refractive capabilities. We'll get into that in just a little bit and essentially, ah, light is going to move through the cornea through the lens and then get focused onto the retina, which is the back of the eye that contains photo receptors. Let me jump out of the way here. So this area at the back of the eye is the retina and light is going thio, enter cornea, get refracted through the lens and project some image onto the retina paying. That is where our photo receptors are, and they will take it from there. So with that, let's flip the page and actually see how those photo receptors work

These light signals are transducer in our photo receptors in the retina, and we actually have two types in the human eye rods and these other types called cones, that we'll get to in just a moment now, rods or photoreceptors that are capable of detecting lower levels of light. However, they're not capable of detecting color of light. So these air sort of like our black and white receptors. They're usually found around the outer edges of the retina and make up more of our peripheral vision. But that's not the case with all organisms. For example, cats tend to have lots of rods, uh, in their retinas, and not just on the outer edges, so that they can see better in the dark. Since you know they are are they tend to be nocturnal hunters. No reduction is the light sensitive receptor protein that's actually going thio. You know, do the photo transaction in rods, and it's composed of two components. Retinal an option. Retinol is a light absorbing molecule. It's actually a form of vitamin A. That's why just another reason it's important to take your vitamins an option is a light sensitive protein. Now what's going to happen is retinol will absorb light and this is going thio rearrange its structure and cause a confirmation. I'll change in option and basically it's going to act as a G protein receptor that will lead to the opening of sodium ion channels. And you can see a little model of that here. So if light and I'm just gonna use a sort of lightning bolt arrow if light strikes read option, it's going thio cause, uh, retinol to absorb it. And that's going to cause a change in the structure. And here, you see, they'll actually split in. The option will go and, you know, ultimately act as a g protein, too. Open this ion channel and you can see what a Rod looks like. Sort of big picture wise over here. Uh, you know, it's not your typical looking nerve cell. It has some weird structures. It does have, you know, a synaptic body and, you know, sell body with the nucleus. That's kind of normal looking. But, you know, then this stuff all up here is just bonkers. And the read option is going to actually be stored in this outer segment that has thes uh, in folded membranes all through here. That's what that pink line is thes in folded membranes, and that's going to contain the read option and have it ready to go when light strikes. Now cones are the photo receptors that we use for color vision. And unlike rods that can pick up low levels of light, these really function best in bright light. And they use different pigments to absorb different wavelengths of light. You can actually see a really nice chart right here that shows you the absorption of blue cones, green cones and red cones, three types of cones we have in our eyes. And, you know, maybe if you've ever seen a projector with the three different colored bulbs in it, you might have noticed that those are actually blue, green and red bulbs. Now you can also see Rod's absorption here kind of in the middle. In the middle of all these, however, I do want you to note that it's gonna be picking up light in, you know, a range that has a decent amount of energy. That's that's the only thing I want to convey their Now the phobia is a special part of the retina. It's a little pit in the back, sort of in the center of the retina, and it's gonna be packed with cones. And this is so that as light enters the eye, the center of our you know, our field of photo receptors is gonna have tons of these cones. And that's going to be the central point for light to be focused on. And so that's going to give us the clearest possible image. You know, when we translate all those signals in our brain and you can see a cone structure here. It's not, uh, terribly similar to A Rod's, but it has that same component of the outer segment with the in folded membrane that's going to contain the photo pigment, Uh or rather, the pigment used for photo reception. However, of course, its outer segment is shaped more like a cone, whereas the rods outer segment is shaped more like a rod. And scientists just aren't very creative when it comes to naming most of the time. So with that, let's go ahead and turn the page

our retinas have three types of nerve cells photoreceptors, bipolar cells and ganglion cells. And they're arranged in three layers. Kind of like a stack. So here we have the back of our rat now, And here is the front where the light is going to be coming from now. You'd probably expect the photo receptors to be right up at the front to greet these waves of light coming in. But you'd be wrong. Evolution is not perfect, remember? So our photo receptors are actually found all the way at the back. I'm just gonna jump out of the way here so you can see what I write. These are photo receptors and you can see we have rods here on the outer edges of our retina and in the center is where we have cones. So obviously we have many more photo receptors that are being shown here. In this diagram. I just want to point out that the cones are concentrated in the center of the retina. Remember, in that area called the phobia and the rods air more concentrated on the peripheries. Now this middle layer, which has this yellow line through it here is where our photo receptors connect to the bipolar cells. And these bipolar cells, which you can see here, are going to bring information from the photo receptors to the ganglion cells. And it should be noted that the ganglion cells take input from multiple bipolar cells. So in essence, ganglion cells air really receiving input from multiple rods and cones at the same time because they synapse on more than one bipolar cell. So the way this communication works is also has some interesting facets to it. That is that the photo receptors and bipolar cells actually have grated potentials, not action potentials. But the ganglion cells are what send action potential. So here we have graded potentials sent through the photo wrists or the photoreceptors create graded potentials based on light coming in. They cause the bipolar cells to have graded potentials and multiple bipolar cells synapse on a ganglion cell and they can lead the ganglion cell tow actually produce an action potential. Now, remember that the receptor potential is generated by hyper polarization from the opening of ion channels and that, uh, this is, you know, a little strange, little different from what we're used. Thio. Uh, you know. Normally we think of deep polarization leading to action potential. But in this case, we actually have a hyper polarization that will then be translated into an action potential by the ganglion cells. Now the ganglion cells, axons, form the optic nerve and actually bring the information to the brain to be turned into something useful. Now, the reason I went with this image, even though this one looks a little nicer, is because I just wanted to convey that the ganglion cells are gonna be synapse ing on multiple bipolar cells, which you don't really see too much of in this image. So even though it's a little prettier, it labels everything nicely for you. I wanted to make sure that, you know, I stress the point that ganglion cells are receiving inputs from multiple rods and cones. Now, this information, when it comes to the brain, you know, it has to be interpreted. It's just mishmash, really. You know, here we have a really nice image. I'll jump out of the way. Eso you can see it better. That sort of illustrates how this happens. So here we have. You know what the eyes air looking at and the rods and cones. They're gonna produce different outputs of that image. The rods they're going to sort of form a black and white version, and then our cones, they're going to show colored versions. This is going to have to be processed to detect different types of color edges you can see. And that's going to be, you know, played with in many different ways. And all of these different, uh, facets of the image put together to actually develop something that looks like this, you know, essentially different parts of the visual cortex. They're gonna play with this information in different ways, and then that all has to be integrated. So each of these frames is just showing you sort of like a different version of what some group of cells is going to process and output in that all has to get eventually put together to create meaningful representations of the world around us. Now, it should be noted that we actually have what's called binocular vision, right? We have two eyes, so we actually get to images of the world around us. And it should be noted that, you know, these images aren't exactly the same because if you think of each of our eyes is a camera, then our cameras Aaron very slightly different positions. But that is the key to our ability to perceive the world in three dimensions or perceive a sense of depth. I should say, you see, by taking essentially two pictures from slightly different angles are brain concurrent pair. Those two images look at the differences between them and from that generate a sense of depth. So pretty sophisticated processing has to happen to this simple visual input in order to actually generate anything meaningful from it. With that, let's go ahead and flip the page.

chemo reception is the detection of chemicals, and it's mediated by chemo receptors, which are what will use for our sense of taste and our sense of smell. Thes chemo receptors change their membrane potential when a specific type of compound is present. Gus Station is what we call our sense of taste, and this is mediated by taste receptors, which are receptors in the taste buds on the tongue. They'll respond to molecules called taste INTs that stimulate thes taste receptors. And they're going to be different varieties of tastings that correspond to the different flavors we can perceive. Those flavors air salt, sour sweet, what's called Mommy and Bitter. The flavor of salt comes from tastings that are electrolytes, specifically sodium acids. Specifically, hydrogen protons will result in these taste. Sour carbohydrates like glucose will taste sweet to us Mommy, which is sometimes described as the fifth taste, and there's actually Japanese Word comes from proteins and amino acids like glutamate. That's that's sort of, um, you know, taste. You get, for example, from eating like a greasy burger or something that that unctuous mommy flavor you get from the meat. It's just tasting the proteins in there really and bitter is used to identify poisonous compounds. That's why we have that awful taste of bitter that makes you go what it's, you know, an evolutionary mechanism to hopefully get you to reject poisons based on their taste. Here you can see a taste receptor or rather, a taste bud with taste receptors in it. And this taste bud will be found all over the tongue here. And it's worth noting that salt and sour receptors actually have the same ion channels to detect their case stints. Uh, interesting to note, because they're both looking for ions right now. Olfaction is what we call our sense of smell. And this is mediated by olfactory receptors, which are chemo receptors that bind odorous, odorous air like tastings. For our knows, they're airborne molecules that air smelled and essentially, uh, thes odorous will make their way into our knows where they will bind to olfactory receptors. Now we have this special part of our brain called the olfactory bulb. In humans, it's not nearly as big as it is, for example, in rodents where it's massive structure. This is the part of the brain that allows us to process this smell information and we actually have these areas called gla Maria line Were olfactory neurons of the same receptor converge. So here in this figure, you can see we have all of these different types of receptors along here. Now you can see that they are all different colors. However, you know, in this model, the blue receptors air all going to be picking up the same types of odorous the red receptors, they're gonna be all picking up the same type of odorous. And the green receptors are all going to respond to the same type of odorous. So even though there interspersed with each other, they're all going to converge in the different GLA Mary ally up here. And you can see that those have been segregated based on whether they're blue, red or green. Now it's worth noting that we actually respond to a special class of chemicals secreted to the environment called pheromones. These are you could almost think of is like a very special type of odorant because they're signaling molecules and they'll actually affect the behavior and physiology of individuals in the same species. And we actually have a special part of our olfactory bulb called the vomeronasal organ that is specifically designed. Thio respond to those pheromones and has pheromone receptors. That's all I have for this lesson, guys. Hopefully now you have a little better understanding of how you see the world pun intended. I'm sorry. See you guys next time.