Peripheral chemoreceptors | Respiratory system physiology | NCLEX-RN | Khan Academy

Summary

The script explains the anatomy of the human heart, focusing on the aorta and its branches, including the right and left common carotid arteries. It details the division of these arteries into internal and external branches and highlights the carotid sinus and aortic arch as locations for baroreceptors, which regulate blood pressure. The script then delves into chemoreceptors, specifically the carotid and aortic bodies, which detect oxygen, carbon dioxide levels, and pH in the blood. These chemoreceptors, comprised of glomus cells, communicate with neurons via neurotransmitters to signal changes in blood chemistry to the brain, with the glossopharyngeal and vagus nerves transmitting this information.

Takeaways

• 💓 The human heart is sketched with emphasis on the aorta and its key branches, particularly those leading to the head, neck, and arms.
• 🔍 The right common carotid artery is highlighted, which splits into the internal and external carotid arteries.
• 🔎 A similar process is described for the left side, with the left common carotid artery also splitting into internal and external branches.
• 🧐 The carotid sinus, an open area in the carotid artery, is identified as the location for baroreceptors, which detect blood pressure and stretch.
• 🌡️ Baroreceptors are crucial for blood pressure regulation by sending information about vessel stretch or pressure back to the brain.
• 🧬 The focus shifts to chemoreceptors, which are responsible for detecting oxygen levels, carbon dioxide levels, and blood pH.
• 📍 Chemoreceptors are located in the aortic body and carotid body, which are slightly different from the baroreceptors' location.
• 🌀 The carotid body is described as receiving some of the highest blood flow rates in the body, emphasizing its importance.
• 🩸 The script explains the role of glomus cells in the carotid and aortic bodies, which detect changes in oxygen and carbon dioxide levels and initiate a response.
• 🚨 A low oxygen level in the blood triggers depolarization in glomus cells, leading to the release of neurotransmitters and action potentials to signal the brain.
• 🔋 The glomus cells' response to high carbon dioxide levels involves the buildup of CO2 in the tissue, leading to increased neurotransmitter release and action potential signaling.

Q & A

What is the primary vessel discussed in the script?

The primary vessel discussed in the script is the aorta, specifically the aortic arch.

What are the key branches of the aortic arch that are mentioned?

The key branches of the aortic arch mentioned are those that go up to the head and neck and those that go out to the arms.

What is the function of the right common carotid artery?

The right common carotid artery eventually bulges and splits into the internal and external branches, which serve different parts of the head and neck.

What are the carotid sinuses and where are they located?

The carotid sinuses are open areas or spaces located in the internal side of the carotid arteries where baroreceptors are found.

What is the role of baroreceptors in the body?

Baroreceptors are nerves that detect stretch or pressure in the vessels and send information back to the brain to help regulate blood pressure.

What are chemoreceptors and what information do they provide?

Chemoreceptors are specialized cells that provide information about oxygen levels, carbon dioxide levels, and pH of the blood.

Where are chemoreceptors located in relation to the aortic arch and carotid arteries?

Chemoreceptors are located in the aortic body and carotid body, which are slightly different from the locations of baroreceptors.

What is the significance of the carotid body's blood flow rate?

The carotid body has one of the highest blood flow rates in the human body, approximately 2 liters per minute for 100 grams of tissue.

What are glomus cells and how do they relate to oxygen detection?

Glomus cells are specialized cells in the carotid and aortic bodies that detect low oxygen levels by depolarizing when oxygen molecules diffuse into them.

How do glomus cells respond to high carbon dioxide levels?

When carbon dioxide levels are high, it becomes difficult for CO2 to diffuse out of the glomus cells, leading to a buildup of CO2 and a subsequent increase in neurotransmitter release and action potentials.

What is the connection between glomus cells and the nervous system?

Glomus cells communicate with neurons through the release of neurotransmitters in response to changes in oxygen and carbon dioxide levels, sending signals to the brain via the vagus nerve and glossopharyngeal nerve.

Outlines

00:00

🫀 Anatomy of the Heart and Arteries

The paragraph begins with a sketch of the human heart, focusing on the aorta and its branches. The aortic arch is highlighted, with emphasis on the right common carotid artery and its division into the internal and external branches. The left common carotid artery is similarly described. The paragraph then introduces the concept of carotid sinuses and their role in housing baroreceptors, which are nerves that detect pressure changes in the blood vessels to regulate blood pressure. The focus shifts to chemoreceptors, which are located in the aortic body and carotid body and are responsible for detecting oxygen levels, carbon dioxide levels, and pH in the blood. The paragraph concludes with a visual aid, zooming in on the carotid and aortic bodies to illustrate their structure and function.

05:02

🔬 Functioning of Chemoreceptors and Glomus Cells

This paragraph delves into the functioning of chemoreceptors, specifically the glomus cells found in the carotid and aortic bodies. It explains how these cells detect low oxygen levels by the diffusion of oxygen molecules into the cell. The paragraph describes the process of depolarization that occurs when oxygen levels are low, leading to the release of neurotransmitters and the generation of action potentials. The role of carbon dioxide in this process is also discussed, explaining how high CO2 levels can lead to increased neurotransmitter release due to difficulty in diffusing out of the cell. The paragraph further explores the chemical reaction of CO2 binding with water to form H2CO3, which can lead to a high proton concentration and low pH, both of which can trigger more action potentials. The paragraph concludes with a note on the evolutionary relationship between glomus cells and nerve cells, sharing a common ancestor in the neuroectoderm.

10:03

🌐 Nervous System Integration of Chemoreceptors

The final paragraph discusses the integration of chemoreceptor information into the nervous system. It describes how the neurons from the carotid and aortic bodies converge to form the glossopharyngeal nerve (cranial nerve number 9) and the vagus nerve (cranial nerve number 10), respectively. These nerves carry information from the peripheral chemoreceptors to the brain. The paragraph emphasizes that these nerves are not part of the brain but are essential for transmitting chemical information detected by the chemoreceptors to the central nervous system. The summary underscores the importance of these peripheral chemoreceptors in the body's ability to respond to changes in blood oxygen, carbon dioxide, and pH levels.

Keywords

💡Aorta

The aorta is the main and largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen. It carries oxygenated blood to the rest of the body. In the video, the aorta is described as having key branches that supply blood to the head, neck, and arms, highlighting its central role in the circulatory system.

💡Aortic Arch

The aortic arch is a large, curved section of the aorta that is located just after the heart and before it descends into the abdomen. It gives rise to major arteries that supply blood to the brain and upper body. The video script mentions the aortic arch as having branches that are crucial for blood supply to the head and neck.

💡Carotid Arteries

The carotid arteries are two major arteries that supply blood to the brain, neck, and face. They are named 'common' because they eventually split into internal and external branches. The video script describes the right and left common carotid arteries and their respective branches, emphasizing their importance in cerebral circulation.

💡Baroreceptors

Baroreceptors are specialized nerve cells located in the walls of certain blood vessels, including the carotid sinus and aortic arch. They detect changes in blood pressure and send signals to the brain to regulate it. The video explains that baroreceptors are sensitive to stretch or pressure in the vessels, playing a critical role in blood pressure homeostasis.

💡Chemoreceptors

Chemoreceptors are sensory receptors that detect changes in the chemical composition of the blood, such as oxygen, carbon dioxide, and pH levels. They are located near the baroreceptors but serve a different function. The video script discusses chemoreceptors' role in monitoring blood chemistry and how they signal the brain about changes that could affect respiration and circulation.

💡Carotid Sinus

The carotid sinus is a dilated area in the carotid artery that contains baroreceptors. It is sensitive to changes in blood pressure and plays a role in the regulation of heart rate and blood vessel diameter. The video script refers to the carotid sinus as a location where baroreceptors are found, contributing to the body's blood pressure control mechanisms.

💡Carotid Body

The carotid body is a small, oxygen-sensitive organ located near the carotid arteries. It contains chemoreceptors that detect low oxygen levels in the blood and send signals to the brain to increase breathing rate and heart rate. The video script describes the carotid body's high blood flow and its role in sensing oxygen levels, emphasizing its importance in respiratory regulation.

💡Aortic Body

The aortic body, also known as the aortic chemoreceptor, is a cluster of chemoreceptors located near the aortic arch. Similar to the carotid body, it detects changes in blood chemistry and sends signals to the brain. The video script explains that the aortic body, like the carotid body, is a 'body of tissue' involved in chemoreception.

💡Glomus Cells

Glomus cells, also known as type I cells, are specialized cells found in the carotid and aortic bodies. They are sensitive to oxygen levels and play a critical role in the chemoreceptor response. The video script details how these cells detect low oxygen levels, leading to depolarization and the release of neurotransmitters, which in turn signal the brain about the blood's oxygen status.

💡Neurotransmitters

Neurotransmitters are chemical messengers that transmit signals across a synapse from one neuron to another. In the context of the video, neurotransmitters are released by glomus cells in response to changes in blood oxygen and carbon dioxide levels. The script explains that the release of neurotransmitters from glomus cells triggers action potentials in neurons, which then communicate this information to the brain.

💡Vagus Nerve

The vagus nerve, also known as cranial nerve X, is a major nerve that plays a role in several bodily functions, including heart rate, digestion, and respiratory rhythm. In the video, the vagus nerve is mentioned as the pathway through which signals from the aortic body are transmitted to the brain, highlighting its role in the body's response to changes in blood chemistry.

💡Glossopharyngeal Nerve

The glossopharyngeal nerve, or cranial nerve IX, is involved in various functions such as sensation in the throat and regulation of blood pressure. The video script describes how the glossopharyngeal nerve carries signals from the carotid body to the brain, similar to the role of the vagus nerve for the aortic body, emphasizing its role in the peripheral chemoreceptor system.

Highlights

Introduction to sketching the human heart and labeling key vessels.

Identification of the aorta as the largest vessel and its arch.

Description of the aortic arch's branches to the head, neck, and arms.

Focus on the right common carotid artery and its internal and external branches.

Explanation of the carotid artery's bulging and splitting into internal and external branches.

Naming convention for the internal and external branches of the left common carotid artery.

Discussion on the carotid sinus as an open area for baroreceptors.

Function of baroreceptors in detecting pressure and stretch in vessels to regulate blood pressure.

Introduction to chemoreceptors and their role in sensing oxygen, carbon dioxide, and pH levels.

Location of chemoreceptors in the aortic body and carotid body, distinct from baroreceptors.

Visual representation of the carotid body and aortic body with their respective vessels and tissues.

Explanation of the carotid body's high blood flow rate and its significance.

Description of the glomus cells in the carotid and aortic bodies and their function.

Mechanism by which glomus cells detect low oxygen levels and depolarize.

Process of neurotransmitter release from glomus cells in response to low oxygen or high carbon dioxide levels.

Connection between glomus cells and neurons through the release of neurotransmitters.

Impact of high carbon dioxide levels on the glomus cell and its response.

Chemical reaction of carbon dioxide with water forming H2CO3 and its breakdown into bicarbonate and a proton.

Evolutionary connection between glomus cells and nerve cells through the neuroectoderm.

Role of the vagus nerve and glossopharyngeal nerve in transmitting information from peripheral chemoreceptors to the brain.

Transcripts

I'm going to quickly sketch out the human heart.

We're also going to label some vessels coming off of it.

So the big vessel, of course, is the aorta.

This is the giant aortic arch.

And the aortic arch has a couple of key branches

that go, for example, up to the head and neck.

It has other branches as well that go out to the arms.

But these branches that are going up

are the ones I'm going to focus on.

So out here on this right side, we

have the right common carotid artery.

And it's called the common because, eventually,

what's going to happen is it's going to bulge here,

and then it's going to split.

And it's going to split into the internal branch-- this is going

inside-- and the external branch over here.

So this would be called, for example,

the right external carotid artery.

And the same thing is happening on the other side,

and we name it kind of the same way.

We say, OK, there's an internal branch and an external branch.

This would be the internal, and this

might be the external branch of the left common carotid artery.

So I think you're getting the idea now.

These are named exactly the same way.

And these are the ones we're going to focus on.

Now, previously, we had talked about how,

in these particular locations, in the internal side and then

this bulgy side, we have what are called the carotid sinus.

Or sinuses, I suppose.

But the carotid sinus is right there.

And the sinus refers to any open area or open space.

And there's also an area over here in the aortic arch.

And these two areas, they are the home for our baroreceptors.

Our baroreceptors are basically little nerves

that are going to detect pressure.

So they're going to detect stretch, or pressure,

that is in the vessels.

And they're going to give information back to the brain.

And that's going to help regulate our blood pressure.

Now, in this video, we're actually

going to focus on chemoreceptors.

Chemoreceptors are also important in giving us

information, but they're going to give us

information about things like oxygen levels, carbon dioxide

levels, pH of the blood, things like that.

So these chemoreceptors-- and this

gets confusing-- they're located in a similar region, but not

exactly the same region.

I'm actually going to shade in where our chemoreceptors might

be, and then also you might get some over here.

So these three areas are where chemoreceptors are.

And they're very, of course, closely

related to where the baroreceptors are,

but they're actually in slightly different locations.

And we call them the aortic body and the carotid body.

And the reason we use the term "body" is

that it's a body of tissue.

So that's why that word gets used.

And this is actually-- you can see now

a slightly different location, and certainly a different job.

So let me blow up some of these regions

and show you, close up, what this might look like.

So let me draw for you the carotid body on this side,

and on the other side, we'll do the aortic body.

And I'm basically just zooming in on it,

so you can see up close what this might look like,

so you can visualize it.

So for the carotid body, you might have the external artery,

the internal artery.

And coming off of the external artery,

you might have little branches, little branches serving

this tissue that's in the middle.

And these branches, of course, are going to branch some more.

And you're going to get all the way down

to the capillary level.

And once you have little capillaries in here,

there's going to be a bunch of little cells.

And these cells are, of course, going

to get the nutrition from the capillary.

And taken together, all these cells--

if you zoom out of this picture, this

would be a little body of cells or body of tissue.

And that's why we call this the carotid body.

And really, the same thing is going on on the aorta side.

So on the aorta side, you've got little branches

coming off of the aorta, of course.

And these branches are going to branch again,

and again, and again, and again.

And eventually, you're going to get

lots and lots of little capillaries.

And these capillaries are going to serve

all these little blue cells that I'm drawing here,

and these are the chemoreceptors that we're talking about.

So these blue cells together make up a body of tissue,

and that's where we get the term "aortic

body" and "carotid body."

Now, on the carotid side, one interesting fact

is that this body of tissue gets a lot of blood flow,

in fact, some of the highest blood

flow in the entire human body.

It's about 2 liters per minute for 100 grams.

And just to put that in perspective

for the carotid body, imagine that you

have a little 2-liter bottle of soda.

I was thinking of something that would be about 2 liters,

and soda came to mind.

And you can imagine pouring this soda out

over something that's about 100 grams-- maybe a tomato.

That's about a 100-gram tomato.

And if you could do this in one minute,

if you could pour out this bottle in one minute,

imagine how wet this tomato's going

to get, how much profusion, in a sense,

this tomato is going to get.

That is how much profusion your carotid body gets.

So it really puts it in perspective

how much blood flow's going into that area.

So let's now zoom in a little bit further.

Let's say I have a capillary.

And inside my capillary, I've got a little red blood cell

here, floating around.

And my red blood cell, of course,

has some hemoglobin in it, which is a protein.

And this protein has got some oxygen bound to it.

I'm going to draw little blue oxygen molecules.

And of course, there's some oxygen

out here in the plasma itself as well.

And if we're in our carotid body or aortic body,

you might have these special little blue cells

that I've been drawing, our peripheral chemoreceptor cells.

And specifically they have a name.

These things are called glomus cells.

I had initially misstated it as a globus cell.

But actually it's an M-- glomus.

And these oxygen molecules-- these

are oxygen molecules over here-- are

going to diffuse down into the tissue

and get into our glomus cell.

It's going to look something like that.

And if you have a lot of oxygen in the blood, of course,

a lot of molecules are going to diffuse in.

But if you don't have too much in here, then not too much

is going to make its way into the cell.

And that's actually the key point.

Because what our cell is going to be able to do is

start to detect low oxygen levels.

Low oxygen levels in the glomus cell

tells this cell that, actually, there

are probably low levels in the blood.

And when the levels are low, this cell

is going to depolarize.

Its membrane is going to depolarize.

And what it has on the other side

are little vesicles that are full of neurotransmitter.

And so when these vesicles detect that, hey, there's

a depolarization going on, these vesicles

are going to dump their neurotransmitter out.

And what you have waiting for them

is this nice little neuron.

So there's a nice little neuron waiting patiently for a signal,

and that signal is going to come in the form

of a neurotransmitter.

So this is how the communication works.

There's going to be a depolarization,

the vessels release their neurotransmitter,

and that is going to send an action potential down

to our neuron.

And if the oxygen levels fall really low,

let's say they get dangerously low,

where the cell is very unhappy, then

you're going to get much more neurotransmitter getting dumped

out, and you're going to get many more action potentials.

So this is how the glomus cell helps to detect oxygen.

And in fact, it also detects carbon dioxide.

Because, remember, this cell is going

to be making carbon dioxide.

Let's say this is a little molecule of CO2,

and that CO2 is going to diffuse out and into the blood.

Well, let's say that the blood has a lot of carbon dioxide

already.

Let's say that it's loaded with carbon dioxide, lots and lots

of it.

In this situation, it's going to be very difficult for carbon

dioxide to make its way from the glomus cell

all the way out into the plasma.

And as a result, carbon dioxide starts building up.

The tissue starts gathering more and more CO2,

because it can't go anywhere.

And this glomus cell is going to say, hey, wait a second.

Our CO2 levels are starting to rise.

There are high CO2 levels.

And again, that's going to make the cell unhappy,

and it's going to send out more neurotransmitter,

and it's going to, of course, send out

more action potentials.

So two different reasons why you might get action

potentials coming out of this glomus cell.

And now I want to remind you that there's

this little formula.

There's this formula where carbon dioxide binds

with water, and it forms H2CO3.

And that's going to break down into bicarbonate and a proton.

So this is our formula.

So if CO2 levels are rising, like the example

I just offered, then the proton level must be high as well.

So a high proton concentration-- I'm

going to put it in brackets, to indicate concentration.

Or another way of saying that would be a low pH.

So these are the things that are going

to make our glomus cell send off more action potentials.

So if you're like me, you're thinking, well, wait a second.

This is really interesting.

Our cell is depolarizing.

It can depolarize.

It also has this neurotransmitter

that I mentioned.

Our glomus cell, then, right here in blue,

is basically sounding a little bit

like it has properties of a nerve cell.

This is a nerve cell.

And the reason for that is that, if you actually take a look,

these two cells have a common ancestor cell.

And so in development, when the fetus is developing,

there is a type of tissue called the neuroectoderm.

And both of these cells, this nerve cell

and this glomus cell, both are derived

from this neuroectoderm.

So it makes sense that they would

have a lot of common features.

So we know the glomus cell is not a neuron,

but it's going to be talking to neurons.

In fact, you're going to have many neurons working together

in this area.

And they're going to join up, both in the aortic body

and the carotid body.

And these neurons, going back to the original picture,

are going to meet up into a big nerve.

And this nerve is going to be called the vagus nerve.

The vagus nerve is going to be the one for our aortic body,

sometimes also called cranial nerve number 10.

And up here with the carotid body, we have a nerve as well.

This is another nerve.

This one, we call the glossopharyngeal nerve.

So these two nerves, the vagus nerve

and the glossopharyngeal nerve-- this one,

this glossopharyngeal nerve, by the way,

is cranial nerve number 9-- these two nerves are not

part of the brain.

They're headed to the brain, right?

So these two nerves are fundamentally

taking information from chemoreceptors

that are outside of the brain.

They're not located in the brain, right?

They're peripheral, and they're taking information

about chemicals and taking that information to the brain.

That's why we call them-- these blue areas, the carotid body

and the aortic body-- we call them peripheral chemoreceptors.