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smell and taste two organs very close related yeah coffee can remind me of different things

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during the morning and wake me up but also why did i feel that sense because i have my sense of a

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smell and my sense of taste. We're going to study them both today, chemoreceptors, smell

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and taste. Let's start with one of the most primitive senses that we have, sense of smell,

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2.2 smell. If we cut our head here in the middle and we see through our nose, this is

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what we will see basically we will see nasal cavity that is the area where all

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the air is going to get into the body we have healed the nose trills with some

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hairs that we have seen in the respiratory system that are very

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important to lubricate and to moisten and to warm temperature and also to

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trap some substances that could be bad for our body because also when we are

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inhalating we get the oxygen but we also can't have viruses we can't have

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pollution we can't have very really bad substances inside of ourselves but let's

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think of something a little bit more exciting food so imagine that we are

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eating something and we smell it first these chemical substances of this dish

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is going to get inside our nasal cavity I have made these substances in green

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and red we cannot see them but we inhale them and they get inside our nasal

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cavity yes some of them will get into the air and be trapped there some of

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them we swallow and we get into our digestive system but most of them will

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go up until they get to the olfactory mucosa this mucosa is a a place where the neurons are going to

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have some of their of the dendrites to detect these chemical substances these dendrites are

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going to drop these chemical substances diluted with the mock mucus that we have on this area

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with this dilution this dendrites send the nerve impulse into the olfactory nerve which is going

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to carry the information up to our brain this nerve is going to go directly into our cerebrum

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onto our frontal lobe in the frontal lobe there's going to be the identification of all the

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different others that we can perceive but also there is some part that will go to the hypothalamus

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the hypothalamus is the area of all sensations and it's going to remind us of something good

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something bad something maybe that we have smell years and years ago but we are really happy to

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have smelled this time here what we have in our olfactory mucosa are different neurons

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that are going to detect different odors. One neuron, one odor. So we have, as you can imagine,

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hundreds and hundreds of neurons here that are going to detect the different odors. It's not

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the same the odor of a mandarin, like the odor of a strawberry, and each neuron is going to detect

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them. We don't have the same neuron for strawberries and mandarin, I can tell you.

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our smell organs are very important for us they are very primitive we already had it when we were

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not even human when we were a simple fish that was swimming into the cambrian period we already

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have the sense of smell why is that important because it's the going to way to recognize the

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environment. We can recognize danger, for example, if we smell burn or we can recognize all the

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people. Imagine a baby when it's born, the only sense that he or she can rely on is the sense of

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smell and he or she will smell his mother or her mother and know that it's her because the sense

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of smell is the most primitive sense that we use. It's so important that five percent of our genes

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five percent of our genome about 400 genes are those that make the sense of smell whereas the

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side that we use it every day and is very useful there are only three genes related to the sense

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of sight maybe you have a here or sense that kobe patients lose the sense of smell about 80 percent

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of the covid patient have noticed some changes in the sense of smell it could be the total lose of

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it that is an illness called anosmia or smell blindness when you cannot sense any anything

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of a smell or maybe to change some of the others that one other that before was good now they

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detected that is not good but also the sense of smell is going to tell us about some illnesses

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like for example parkinson or alzheimer disease if there is a lose of smell it's an early predictor

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of these senses we are talking a lot about food and about smelling but what about tasting let's

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it closely connected with the smell we have the sense of taste we get to our mouth but we also

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have chemical substances that are going to activate certain neurons these neurons are

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the receptors that are going to carry the information from our mouth from the food that we

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to get to our brain. Let's see how they do. What we have here is a drawing of one

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of the taste buds that we have on our tongue. We do not have only the

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sense of taste in our tongue, it's all over our mouth, in our tongue, our teeth,

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our cheeks, our palate, but we are going to focus on the tongue where we

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have most of the taste buds. These taste buds are integrated into the lingual epithelium on

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our tongue. That's why we have an epithelium here in which we have other receptors, like the

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receptors of temperature, the thermoreceptors. We have also receptors of pain. That's why when we

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get something really hot on our mouth we get burned and we feel pain on our on our tongue

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as you see here on the upper part we have the oral cavity so we are going to get substances inside

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and if these substances are going to be dissolved with our saliva these chemical substances we get

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with the saliva and are going to make contact with the microbial this microbial are going to

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be moving, trying to catch substances here on the taste pore, so it's a place that is open to the

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oral cavity, and these microvilli are part of the taste receptor cells. These taste

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receptor cells are neurons, don't forget about it, and when the chemical substance contact them,

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they are going to be excited and they are going to release a nerve impulse.

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this nerve impulse is going to get out of the taste bud by the nerve and it's going to get all

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the way by our nerves to the brain where it's going to get all the information which is going

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to be integrated on our brain on the cerebrum specifically the frontal and the parietal lobe

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There are also other types of cells which are going to support the taste receptor cells.

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These are the support cells, which I made in green here.

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Maybe when you were a child, you have studied this picture here,

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with all the different flavors, saying that the taste flavor is on the front part of our tongue,

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the salty flavor is on the side. Well, that is wrong.

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Sorry, that is wrong.

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we cannot talk about that anymore no because basically all the different taste buds can taste

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all the different flavors it's true that we have certain flavors like the sour flavor which we are

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going to feel more at the back of our mouth why is that because most of the poisons that we could

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get by food are sour so when we eat a venom a poison thing we can activate our defense and we

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can vomit it how many flavors do we have we have at least six or seven flavors we don't have any

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more than four flavors that we knew but food is not only flavors it's also emotions when we eat

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something we remind of so maybe we remind of a certain place of a different situation where we

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have eaten that food especially if it's a good food a really bad food we can think oh this food

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was really good i ate it somewhere and i really like it so when we eat it we eat maybe we eat

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more because we remember it or if we didn't like it it's a this is not good for me i better not

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idiot. Why is that? Because also these nerves end up in the hypothalamus, which is a part of

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our brain, which is going to be responsible for emotions. That's why we can smell, for example,

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a food that we eat in summer, like gazpacho, for example, and we think, oh, I remember I had such

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great time when I was at the swimming pool and I get home and I get that for lunch. Well, that's

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because your tongue is also connected with your hypothalamus and your emotions. Today we have

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studied two of the senses which are chemoreceptors, meaning that they have chemical substances

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related to them, the smell and the taste. We have another two senses left, hearing and seeing

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for next day