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Smell, Taste & Touch

  • Nasal anatomy includes: the nose (nasal bones/cartilage), vestibule, nasal conchae, cribiform plate, and olfactory epithelium
  • Olfaction (sense of smell) begins when odorant molecules come into contact with the hair cells of olfactory epithelium imbedded in mucus
  • Olfactory epithelium is regenerated due to them being more vulnerable than other neuronal networks
  • Smell has a dramatic impact on taste and it has a close link to memory
  • Gustation (sense of taste) is thanks to papillae on the tongue and the gustatory cells contained within them
  • The muscles of the tongue and saliva also play a role in the ability to taste chemicals
  • Taste buds contain gustatory cells, taste hairs, transitional cells, basal cells, and nerve fibers
  • Five main taste categories are sweet, salty, bitter, sour, and umami
  • Genetics plays a role in the sense of taste (as illustrated by PTC paper)
  • The sense of touch is due to stimulation of nociceptors (for pain) and mechanoreceptors (for physical distortion)
  • Pain receptors are sensitive to temperature change, mechanical damage, and caustic chemicals
  • The sensation from mechanical distortion is due to tactile receptors
  • Did you know…
    • Q: Why can’t you tickle yourself?
    • A: Being tickled involves the tickler being in charge of where they’re touching the other person. If a person tries to tickle their own self, they are aware of where they’re going at any given moment and there is no element of surprise. The unknown in terms of which sensory neuronal networks will be stimulated is what makes tickling possible

Smell, Taste & Touch

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Nasal Anatomy 0:05
    • The Nose
    • Nasal Cavity
  • Olfaction 3:27
    • Sense of Smell
    • Olfactory Epithelium
  • Olfactory Receptors 7:23
    • Respond to Odorant Molecules
    • Lots of Turnover of Olfactory Receptor Cells
    • Smells Noticed in Small Concentrations
  • Anatomy of Taste 12:41
    • Tongue
    • Pharynx / Larynx
    • Salivary Glands
  • Papilla Structure 16:56
    • Gustatory Cells
    • Taste Hairs
    • Transitional Cells
    • Basal Cells
    • Nerve Fibers
  • Taste Sensations 19:06
    • Sweet
    • Salty
    • Bitter
    • Sour
    • Umami
    • Water
    • PTC
  • Touch 25:00
    • Nociceptors
    • Mechanoreceptors
  • Nociceptors 26:30
    • Sensitive To…
    • Fast vs. Slow Pain
  • Mechanoreceptors 31:15
    • Tactile Receptors
    • Baroreceptors
    • Proprioceptors

Transcription: Smell, Taste & Touch

Welcome back to

This is the lesson on smell, taste, and touch.0002

When we look at nasal anatomy this main structure that is involved with smelling is the nose which is the most obvious part.0004

It is made up of skin, cartilage, a little bit of fat in there, you also have some bones but this part right here is cartilage and soft bone.0014

The only bony part of the nose is the bridge.0025

These are the 2 nasal bones that has a lot to do with the little arch, the bridge of your nose.0029

If you do break your nose, you tend to break this part up here the nasal bones.0034

A deep enough kind of trauma could definitely fracture parts of the maxillae or even deeper the ethmoid bone0039

Which is found straight through and making up most of the nasal conchae, those weaving passageways deep within the nose.0046

Mostly cartilage that is making up the majority of this structure.0052

The nasal cavity itself there are 2 nostrils that lead into the nasal conchae.0057

Within those nostrils you are going to have hair and mucus.0063

You will see the hairs in this particular drawing, you know that it is there and some people have more than others and some people trim them.0067

The hairs serve a purpose.0073

They are similar to the ear canal, the hair is trapping dirt, particles in going deeper,0074

It is minimizing the chances that you are going to get nasal infections in the upper respiratory tract.0080

The mucous is constantly being produced in the nasal conchae even if you are not sick.0085

That mucous serves numerous purposes.0092

It warms the air that you are exhaling and it is going to catch a lot of stuff that you are inhaling.0095

Those microorganisms, bacteria, viruses, that you do not notice but they are there.0102

When you are more sick you are going to produce additional mucous.0107

The mucous serves a purpose.0113

Even when we are sneezing it out you are producing it and you tend to swallow it because the nasal cavity does connect to the pharynx/throat.0116

Every time you swallow there will be a little bit of the nasal mucous that is going to drift back down your esophagus.0127

That sounds disgusting but it is part of the human body.0134

The conchae are those weaving little caverns named after the fact that they are spirally and twisty and turning like a conch shell.0138

The nasal conchae is formed mostly by that ethmoid bone that we have discussed in the skeletal lessons.0147

On top of those weaving caverns of the ethmoid bone you are going to have those mucous membranes producing the nasal mucous.0152

The curbiform plate is where we focus on for all the action that is going on with your sense of smell.0160

If you remember the ethmoid bone being like an eon inside and these parts of the E are those twisty, turny conchae parts.0167

This was the perpendicular plate that goes vertical.0176

If you go up to the top, the superior portion of the perpendicular plate, there is another part called the curbiform plate.0180

That superior almost perpendicular portion, on top of that perpendicular plate contains the olfactory epithelium.0186

The olfactory epithelium is where you have those layers of cells received those odor molecules and some signals up to your brain.0197

Olfaction is that technical, physiological term for the sense of smell.0206

Olfactory receptor cells are common terms.0214

It is not old factory like an old run down building where they make things.0217

Olfaction comes from Latin and it has to do with your sense of smell.0221

These are the only sense in the body where the olfactory receptor cells are directly adjacent to the outer environment.0227

If you think that the other senses whether it is touch, or hearing, the receptor cells involved in receiving the signaling are just must deeper.0235

Think about the ear, the cochlea that has hair cells sensitive to the vibration that is coming to your ear0245

Are deep inside your head compared with the outer structure of your ear.0254

Not so with the nose, when those odor molecules go up into your nostrils they come into contact with mucous where the hairs,0258

The little cilia of these particular cells are right there.0269

It is great.0273

It is the closest receptor cells to the outer environment.0275

The problem with that is that they can get damaged a lot easier than the neurons of your skin and the neurons involved with taste and hearing.0278

They get generated more often than those other cells can.0288

That is the price you pay for them being so close to the outer environment.0293

Olfactory epithelium is that epithelial layer that is involved with smelling.0297

Olfactory receptor cells are the main cells that are doing the action and I am going to high light them in yellow.0304

Here they are.0310

They have little hairs that extend out.0313

I am drawing them spread out like this because this increases their chances of getting an odor molecule touching them.0321

Having them all spread out just like little roots on the ground in this mucous layer,0333

Having all these little hair spread out this is going to increase the chances of reception.0339

Basal cells are those little cells in this region that are functioning like a stem cell.0343

As these olfactory receptor cells gets damaged, basal cells can go through mitosis and as a cell mature they take the place of damaged or old olfactory cells.0350

Olfactory glands which are not depicted well in this picture are these glands that produce the mucous.0360

That mucous layer that is right in here, that these cilia are actually embedded in, that is where the mucous come from.0368

A little different with the glands with in the skin that they producing mucous that is located in the nasal conchae.0376

The olfactory system can distinguish 2,000 to 4,000 different stimuli.0384

As those odor molecules come up into this passageway and hit the little cilia, it is just like action potentials from precious lessons.0392

As the cilia gets hit those open up channels where the sodium and potassium moves and activates these cells just like another neuron.0399

These are modified to react to odors.0406

If you set and wrote down a list of all the different odors that you remember smelling like orange, lavenders, etc.0409

It will be hard to come to the list of 2,000 to 4,000.0418

We do not always consciously remember that we can smell these different things but in the terms of how the brain reacts to different stimuli,0421

We found that there are thousands of different chemicals that affect your olfactory receptor cells a little bit differently.0433

When it comes to olfactory receptors, like I have mentioned before these are highly modified neurons that respond to odor and molecules.0440

Each one of them has about 20 cilia that extend into the surrounding mucous.0449

As I have mentioned there are the curbiform plate and they are spreading out.0453

You have approximately 20,000,000 olfactory receptor cells in an area of 5 cm3.0458

It is a tiny area with a lot of cells.0466

That is impressive to think about.0470

It is even more impressive to think about an animal like a German shepherd which has 70× that area.0472

Smells to them are much more obvious.0479

When you think about a German shepherd being used in an airport to smell packages, to see if there are contraband or explosives, smells are obvious to that animal.0481

It is like us looking at colors on the ground.0492

When a dog is tracking a smell, it is presumably that obvious.0495

It is fascinating to think what it would be like inside the head of that animal.0500

There is lot of turn over of olfactory receptor cells and this is a rare example of adult neuron replacement.0504

Think about the spinal cord with all the cells running down there.0511

If you damage spinal cord neurons enough you cannot get them back.0515

They are damaged for life that will result in paraplegia or quadriplegia depending on what area you damage.0519

Eventually we will get there with curing those conditions.0523

This is something that naturally happens where because of this neurons are close to the outer environment they tend to get damaged more rapidly.0527

Replacing them enables you to smell the stuff that you like smelling even as an adult.0536

Smells can be noticed in very small concentrations0545

An example is beta and this is a chemical that is added to gases that are naturally odorless like butane, propane, natural gas,0549

Without adding small bits of beta or capping if there was a gas leak in your house or apartment and all the windows are closed,0558

You would not be able to smell that this gas is entering the room and can result to more deaths if we did not have this in there.0565

Just adding a touch of this gas that has an odor saves lives every year. These cells have a dramatic effect on taste.0573

I'm sure you have heard this or experienced this, if you are sick and you have swelling in your nasal region in the upper rest for a track0582

And a lot of additional production of mucus, the food tastes more bland when you are sick.0591

We take this for granted that taste is affected by olfaction.0598

I have heard estimates that up to 50% of taste are impacted by this particular set of cells.0603

Here is a trick you could do at home.0610

If you close your eyes and plug your nose and have somebody put in your mouth a piece of apple and a piece of pear without you knowing which one is which.0611

If they are both the same ripeness, about the same density or consistency it is a really hard without looking and smelling of telling the difference it can apparently be apple.0621

That is one example how smell would assist you with that.0631

I have a relative who actually has a problem with a sense of smell.0635

I did notice until he was helping out my uncle with a construction job they are redoing a room and every one who was on the site was told not to enter the room0640

Because there was really caustic chemical that is actually harmful to inhale and it is a chemical that once you walk in a room you would smell.0649

My relative who has a smelling problem did not hear that announcement.0658

He goes in the room sometime during that day and he does on a mask on and he is working on something and my uncle is like what are you doing here?0661

Do not you smell that?0669

He said smell what?0670

Obviously it will be weird not to smell this.0671

They took him to a doctor and after some test they realize that he only has 10% of the olfaction ability as the average human being.0673

He is missing 90% of what he should be experiencing.0681

I do not know what taste is like to him and we would never know until we get inside his head because0685

he had no idea he was lacking that smelling ability until they confirmed it was some tests.0690

That is interesting to think about.0696

Last thing I want to mention with olfaction is that you already heard this before in the nervous system lessons0698

if you watch those but smell has a profound connection to memory.0703

This is the only one of the five major senses that does not go through the medulla thorough the thalamus.0709

This goes straight up into the part of the cerebrum that leads to cerebral cortex.0715

That actually connects to memory quite a bit0719

If you look at the tracks for olfactor receptors and how they go up into those olfactory bulbs and those little tracks all the way up.0724

They go straight through the areas that have to do with memories.0732

They go right through parts of the limbic system that have to do with memory.0738

The hippocampus is right there.0743

You may have heard that smell is connected a memory greatly it is.0745

If you smell freshly baked cookies and think of grandma that is what we are talking about.0750

Olfaction connected to the memory in a great way.0757

When it comes to taste we got to talk about the mouth of course.0759

The tongue is the major player in your ability to taste but it is not just the tongue.0765

If we do look at the tongue in this particular picture you can see if the person is lifting up their tongue and touching the mouth,0769

the little bumps you do not see quite as many on the other side.0777

It is it is hard to distinguish those but I like this picture because you consider labeling some the salivary glands as you call sublingual which literally means under the tongue.0781

Here is the mouth and here is how the tongue is attached to the mandible bone.0788

And of course you got your gums and the interior cheek, the teeth, etc.0793

Within the tongue itself you have got multiple muscles and these muscles are incredibly strong for their size.0797

I have heard different textbooks say that the heart is the strongest muscle and some say that the tongue is the strongest muscle.0804

The tongue is very strong and that dentists will tell you that the tongue can over time change the position of your teeth.0810

It can actually change how your teeth are laying in your mandible.0819

That is pretty incredible to think about.0825

That is a lot power of power.0827

On the surface of the tongue you have what are called papillae and each one is a papilla.0828

Those bumps you should call them taste buds the proper term is papillae.0833

When you actually see those bumps on the surface of the tongue, the papillae with in them there are taste buds that have these gustatory cells or taste cells.0840

The pharynx is the throat and the larynx is a bit deeper down there but taste is there too.0850

A lot of those taste cells they reduce as you age, as you get to adulthood but the pharynx, the larynx, have a little bit of ability to allow you to perceive some tastes.0857

I will tell you more about that later.0868

Salivary glands they have a lot to do with taste.0870

If it was not for saliva, number one you would not have that aqueous medium that allows the cells of the papillae0874

to get that signal noticed but also within the salivary secretions you have enzymes.0882

Enzymes break down those chemicals, those compounds that you were chewing.0889

Without that enzyme ability you would not be able to perceive those little tastes that you experience on a daily basis.0895

Here is an example of that.0903

One of the many enzymes that salivary glands are releasing is salivary amillae.0904

An amillae is responsible for breaking down larger carbohydrates or sugars into tiny little bits like glucose, monosaccharide.0910

Glucose we perceive as being sweet.0922

Larger carbohydrates like starch do not taste as sweet when they are that big molecular structure polysaccharide.0925

You can try this at home.0933

Normally when you eat a cracker you chew it a few times then swallow it before you get the ability to sense the glucose inside there.0934

There are large carbohydrates that make up breads or crackers.0944

If you chew it and let a little bit sit on your tongue with saliva and just do not swallow immediately, just chew it a little bit and let it sit their for a while,0949

you can actually get this more sweet taste from the little tiny glucose is in the other tiny sugars that are inside a cracker.0961

You are giving your salivary glands a chance to break that down further before swallowing it.0970

Taste cells are scattered all around the mouth and throat like I said there are some on the pharynx and larynx specifically the part of the larynx0976

that you going to see some taste cells on especially in younger people is on the epiglottis.0984

You are going to hear more about that with the digest system.0989

The epiglottis is a flap that closes on the respiratory tract so that when you swallow foods it does not go on your lungs.0991

But you will see that the ability to taste like sugar, the sweetness, sour, bitter, etc, not as profound on the throat and larynx.0999

Most of them are on the tongue and some of them are around the size of the mouth.1010

The structure of a papilla those are the bumps if you take a look at a cross section straight through one of those bumps at the surface of the tongue,1015

here is that papilla and considering this is a cross section you are only seeing part of it.1026

A papilla is round and so around the edge of it there is kind of like this ditch.1033

Here are two sides of the crevice around a papilla and these little guys right here those are the taste buds.1040

Each one of these are taste buds that is why I am calling this a taste but is not proper.1050

This is a papilla.1057

Within a taste bud here is one picture here you have gustatory or taste cells that are afferent.1059

There are sensory neurons that take stimuli up into your CNS.1066

Each one of those cells is right here.1073

We highlight that in yellow.1076

Here is one of these gustatory cells, here is another and here is a third.1078

And you can see that each one of them has this little hair and these little hairs project out into this little crevice and saliva can get into those little areas1084

and that is what is going to enable the hairs to be activated effectively so that you get those action potentials and that reception happening of those different tastes.1096

Transitional cells are the ones that are in between supporting cells for the taste bud.1106

Basal cells like the sense of smell are stem cells that enable you to regenerate these.1112

I have heard that taste cells only last for about 10 days so you do need some of regeneration of them overtime as you lose them.1117

Nerve fibers are right here and they are really axons that come together to form the nerve that goes up into your CNS.1127

When it comes to taste sensations, the major tastes that we experience there are 4 major ones, sweet, salty, bitter, and sour.1145

If you have ever seen one of those tongue maps and says here is the sweet area, here is a sour area, here is a bitter and salty, etc.1155

That is not how it is.1162

You cannot say that this is the sweet part of the tongue.1165

Certain parts of the tongue can be slightly better than others at perceiving certain taste sensations but all of your different taste buds have the ability to notice all four of them.1167

You can try it yourself.1179

Out salt here and back there, you are going to notice the salt all over your tongue.1182

Sweet how does that happen?1188

Sweet sensations come from sugars of course.1190

We breakdown sugars through chewing, saliva, etc.1195

You are going to get that sweetness and of course with breads, with a candy, all of those things that gets those sweet sensations.1199

Glucose, fructose, galactose, etc., are going to activate the gustatory cells in that way.1209

Salty is the most common in NaCl, sodium chloride, there are all kinds of salts.1215

With the chemistry, salt is like a category of ionic compounds.1221

Bitter such as horse radish, bitterness, slightly the bitter sensations like arugula.1227

Arugula taste slightly bitter.1239

I like it some people do not.1241

The way people perceive bitterness can vary.1242

Sour is actually from acids.1245

If you like sour candy you have affinity for acidic molecules.1250

Acids are on the bad wrap, if you have taken chemistry you know that strong acid, the kinds that are actually burn1257

through the surface of your tongue or can harm your skin if you get them on you.1263

We have a lot of acidic foods.1267

Milk is slightly acidic.1271

Tomatoes are slightly acidic.1272

If you go to oranges and lemons you are getting even more acidic.1274

We do consume a lot of foods that are ever so slightly acidic.1277

Fruits or a nice balance between sweet having those natural sugars and a little bit of sour like citric acid.1282

Umami, this 5th one is more recently talked about.1289

It is a Japanese word.1295

Umami, I have heard that in the back of the tongue is even a slightly greater ability to put to perceive this umami flavor.1296

It is been described to me as a savory, meaty, even perfect, as a translation for umami.1304

Sushi in my opinion is a good example of what that umami flavor is all about.1312

Beef broth of all sort of chicken broth is another one that can be slightly different than these four.1318

Water, does water have a taste?1325

You might think no, if there is taste there is something dissolved in the water like metallic ions or something that does not belong there.1328

But water, research has shown that especially in the back of the throat like the pharynx those tastes receptors there do respond to water and send signals to your brain.1336

You may not consciously realize that like this water has a flavor as it goes down.1348

If you take a very long swig of water especially if you are dehydrated, you do sense that water going down1352

and it tells your brain to actually change the amount of ADH being secreted out.1359

ADH is anti diuretic hormone.1365

It is a hormone that allows the body to hold onto water.1367

You will urinate quite as much if you are releasing ADH.1370

If you just drink a lot of water that means you do not need to hang on to quite as much water as you have been.1374

So the fact that the water signals neurons to change something that is happening in your brain we can describe that as a taste sensation.1381

PTC, number 7 I have put it down here because this is a peculiar one.1390

If you have taken biology classes you may have done this.1395

A PTC paper it stands for fennel teal carbomide.1398

PTC papers usually looks like rectangular thin papers and you will pass them to students and say on the count of 3 touch it to your tongue.1402

When they touch it into their tongue after a few seconds people who can actually taste PTC get this profound bitterness.1411

A lot of people can taste it and I have read that approximately 70% of Americans have the genotype to enable them to actually notice PTC.1424

About 30% of people do not.1433

And it is because when you look at the genetics of this it is a dominant allele that allows you to perceive the PTC as this chemical.1435

And if your homozygous recessive, a few inherited those alleles you can't notice PTC.1445

And this is one of the many examples that show you the genetics plays a role in taste.1453

There are probably lots of genes that determine your taste abilities.1457

Some people just do not like broccoli at all.1462

I love broccoli and I do not even need salt and butter.1466

I will just eat it plain but some people, no matter how many times they try broccoli even as an adult and given that many chances they cannot stand it.1469

Now may be compared to me they are able to taste some kind of chemical on the broccoli that I do not.1478

Because I do not notice it I love it.1485

There is a lot out there in terms of genetics and how taste is affected.1487

And I wrote it more because there is lot of genes that impact your taste sensations.1493

When it comes to touch, there are few types of sensory receptors in the skin corresponding to touch.1499

One of the main ones is nociceptors and that is for pain.1507

Pain comes to different forms and we will get to them in a second.1511

Nociceptors in general have to do with pain being perceived.1513

Mechanoreceptors, physical distortion.1517

What is physical distortion?1521

Any time you are touched in a way that manipulates your skin, light, heavy, deep pressure, that is going to be mechanoreceptors that are going to be stimulated.1523

And here is a course a cross section of skin.1539

Epidermis here and on the bottom you got the stratum basale.1542

All of these are the dermis and you can see that these are blood vessels.1545

Here is a curled up sweat gland here is a hair follicle leading to a hair emerging from the root.1549

They are not depicting neurons in here.1554

They are not depicting these little receptors.1558

Here is one example.1560

You can have a little corpus school and you will see what a corpus school is in a bit and their different levels.1561

Some of them are really deep.1569

Some of them are actually much more superficial.1570

This one is right at the top, more superficial part of the dermis just deep to the epidermis.1574

These are scattered all throughout the skin specifically in the dermis.1584

Let us start with pain.1589

Nociceptors, these pain receptors are sensitive to a few different kinds of pain in terms of how the pain results.1592

Temperature of course if you ever had boiling water hit your skin you know that temperature changes can cause pain to occur.1600

And is not just heat, if you had been next to dry ice, they say to not touch dry ice because it is way colder than solid water.1612

Dry ice is solid CO2 and touching it can cause a burn which seems ironic to say burn but it will actually damage your skin1624

and it is not something you want in terms of the pain as a result.1635

Mechanical damage that cuts, lacerations, that is mechanically harming the skin and going to cause pain.1638

Chemicals have a strong acid or strong base and alkaline substance landing on your skin that can cause pain.1648

Now the amazing thing is sometimes one kind of stimulus, one kind of a set of trauma will actually stimulate a lot of different types of pain.1657

That is why some people they will get a wound like a deep cut with a knife but will described it as a hot burning sensation even though it is just mechanical damage happened.1669

Smetimes a certain kind of stimulus can be perceived as various types of pain all at once.1682

When we say fast and slow pain is basically this fast pain is a different kind of neuron track, these are type A fibers, these are type C fibers.1691

Fast paint tends to be stuff like needles, a knife, so if you have gotten a shot, let us say a booster shot on your shoulder and when that needle goes in, it is a fast pain literally.1700

It goes along a certain kind of nerve fiber up to the CNS and you feel it right away.1713

Slow pain tends to be kind of that like that dull aching not as localize like a fast pain.1721

It is like a sharp pain that you know exactly where it is and slow pain sometimes will just be in a general area.1732

And this slow pain actually goes up more into the reticular formation thalamus region more so than the fast pain in terms of how it is perceived.1739

Pain is complex in terms of perception.1750

Scientists and doctors will spend their whole careers on pain and how to treat pain, on how to help with pain in a patient.1754

In terms of the complexity of how pain is perceiving the human body, we do not know all the answers.1766

On you know some people will have nothing wrong with them.1773

They will do tests on their organs, on their whole body, MRI, etc.1778

Sometimes it would not be obvious what is the root of the pain.1783

Wises person having this pain sometimes it is just pain is being perceived by the person chronically and they cannot narrow it down why it is happening.1789

There are medications that can help in terms of lessening those action potentials and lessening the neurotransmitters ability to make pain happen inside your head.1800

That is amazing to think about that.1811

There is something else called referred pain which is pretty fascinating.1813

Referred pain is when people get heart attack will get this numbness and pain all throughout their left arm.1818

Your heart is not here, it is slightly on the left side of the chest but the reason why that referred pain happens is1826

there are similar nerve tracks in terms of how they come into your spinal cord.1832

The nerves in your left arm actually kind of run right into the nerves from the heart.1838

A heart attack will actually affect these nerves in terms of the stimuli coming up into your brain.1844

There is a sensation that something is wrong with the left arm.1851

If that happens in someone you are with call 911 if it gets deep up pain all of a sudden in the left arm.1854

Another one is the gallbladder.1862

Amazingly pain in the gallbladder can be felt up here on the shoulder.1864

It is called referred pain.1869

One of the many fascinating topics associated with nociceptors.1871

When it comes to mechanoreceptors these are in terms of how your skin is literally touched.1874

We can call them tactile receptors because it has to do with literally being touched.1881

Free nerve endings are found all throughout specially the top superficial parts of the dermis.1887

Let us say this is the surface of the epidermis and here is the bottom or deeper part of the epidermis and here is the dermal layer.1895

Free nerve endings these are dendrites will extend up to those superficial parts of the dermis.1908

As you get touched here, they are going to be stimulated.1920

And those are found all throughout the root plexus.1925

Here is a hair shaft, it is thick but it'll do and here is the hair follicle.1929

And of course you are going to have blood supply.1936

You are going to this hair, wrapped around part of the hair shaft is something called root hair plexus.1940

It is being wrapped around here.1948

The amazing thing is when a hair is brushed that is going to stimulate the root hair plexus.1951

Something as simple as like this I can feel it very easily even my fingers when actually touching the surface of my epidermis,1959

this especially happens when you are moving garments around.1967

Here this fabric is not even touching the surface of my epidermis but it is touching the hairs on my arm and that's going to be notice.1971

It is amazing.1982

It is a fine kind of stimulus that is stimulating root hair plexus.1984

Tactile receptors also called Merkel disks.1988

These are also for fine touch and they are extremely sensitive.1992

They look a little bit different.1996

Merkel disks when they extend up they have these little disks.1998

That is pretty much how they look like.2003

Tactile corpus schools also called Meisner corpus schools.2009

These look more like kind of a roundish bulb in a sense.2012

Meisner corpus school looks like this.2020

On these particular corpus schools they had a lot to do with sensing pressure and they are concentrated more in the eyelids, the lips, the fingers, nipples, and the external genitalia.2024

Lamellae corpus schools similar look but the thing that is distinguishing of these corpus schools is it looks like kind of concentric circles, almost like a fingerprint.2041

The lamellae corpus schools have that appearance.2053

You do not see that concentric circle look quite as much in the Meisner ones.2056

These lamellae corpus schools they also correspond to deep pressure.2060

Something not quite as like fine as what I was talking about earlier.2065

It is a deeper pressure.2072

Refini corpus school is when you look at the collagen fibers all throughout the dermis, these are associated with that.2073

When it comes to kind of those deep manipulations of the collagen within the dermis, refini corpus schools are definitely stimulated.2080

Let us say that this is a collagen fiber, you can have these little refine corpus schools enervating just kind of coming in and being a part of all those collagen tracks.2091

Those are located throughout the body.2108

It has to do a little bit with deeper stimulation and some of these other ones but they are there in your skin.2112

Baroreceptors have a lot to do with pressure.2118

We are not as conscious of these but they are on the skin.2122

In terms of the blood vessels that are located especially the deeper parts of your integumentary system, the skin how to do with pressure.2128

For instance on if there is a change in blood volume baroreceptors are going to notice it.2136

If there is a change in blood pressure that is going to cause manipulation of those blood vessels.2142

You are going to see baroreceptors in the aorta and in the carotid arteries.2147

They communicate with the brain literally in terms of how to manipulate blood pressure when it needs to be manipulated.2157

Proprioreceptors have a lot to do with joint position.2166

Intention associated with the joints and the capsule.2170

Your skin is pretty close to a lot of these areas where joints are.2174

Proprioreceptors in terms of how the joints are moving, your brain is going to sense that in terms of the positioning of them and how they are being manipulated.2179

Some tendons and ligaments, joints, have a lot of these that are called proprioreceptors.2191

There is touch, smell, and taste.2195

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