- [Presenter] Even though we're dealing
with the respiratory system,
we have to talk about the nervous system,
because the nervous system is
what will control your respiration rate.
It'll control how many breaths you take per minute.
We have this respiratory center
in the medulla oblongata, that's basically the brain stem.
This helps to establish your breathing pattern.
Do you breathe 12 times a minute,
15 times a minute, 18 times a minute?
It sets how many times you breathe in a minute.
Typically about every five seconds or so,
the neurons are stimulated.
This causes your intercostal muscles
and the diaphragms to be activated.
Usually when you're breathing calmly,
just regular breathing,
it's traditionally just the diaphragm, the muscle
at the bottom of your lungs, that's working.
The intercostal muscles, more often than not,
are simply there for deep breaths or forced exhalation.
Why do we breathe?
We breathe to bring in oxygen
and get rid of carbon dioxide, CO2.
One thing your body must do is monitor
the carbon dioxide levels
to see if you have too much or too little.
If your carbon dioxide--that's the up arrow P CO2,
If the partial pressure of carbon dioxide
in your blood goes up,
it causes too many hydrogen ions, H+,
in your cerebrospinal fluid.
Cerebrospinal fluid, that's the stuff
that's around the brain.
It's around the spinal cord.
If that happens, the brain and spinal cord will realize
and say, "Hey, we've got a problem here.
"Let's increase our respiratory rates."
By breathing faster, it means you'll have more opportunity
to get rid of carbon dioxide.
So the increased respiratory rate helps
to get rid of an increase in carbon dioxide.
This really is the main, or primary,
regulation of respiration.
You're not necessarily looking for oxygen.
You're looking for carbon dioxide,
because the two are linked, true.
Usually if you have more carbon dioxide,
you have less oxygen.
If you have more oxygen, you have less carbon dioxide.
But it's this increase in carbon dioxide
that changes the hydrogen ion level.
It's that hydrogen ion level that really makes a difference.
Just because carbon dioxide is the main
controlling factor for respiration
doesn't mean you ignore oxygen.
You still monitor your partial pressure of oxygen, P O2.
In your aorta--
that's the major blood vessel coming off your heart,
and your carotid bodies--
those are the major blood vessels running up to your brain,
you're gonna monitor your oxygen levels.
If your oxygen levels fall too far down, or too low,
those bodies are automatically activated.
By activating, it'll increase your respiratory rate,
but also increase the depth of breathing.
What's happening here now is,
just like carbon dioxide, you're breathing faster,
but you're also breathing deeper,
bringing more air into the lungs.
The more air you breathe in,
the better chance and higher rates of oxygen diffusion,
getting oxygen into your body.
The rates and depth of normal breathing,
what you're doing right now,
is determined by the fact that you need
to get rid of carbon dioxide.
It's not necessarily because you need the O2,
you need the oxygen,
it's more because you're trying to get rid
of the carbon dioxide.
When you get rid of the carbon dioxide,
your body automatically picks up more O2.
So really the main driving factor behind normal breathing
is the fact that your body must get rid of carbon dioxide.
Can we modify our breathing?
Sure, we have some ability
to consciously control our breathing.
For instance, if I said right now,
"Increase your respiratory rate,"
you could start to breathe faster.
In out, in out, in out.
But if I said, "Slow it down,"
you could slow it down a little bit.
Breathe a deep breath and slowly
and slowly exhale out.
But you can only maintain this for a certain period of time.
Speaking, singing, are also modifications of breathing.
When you're singing a song,
do you stop right in the middle of a word
to take a breath usually?
Or you're speaking.
Are you also gonna be saying a word
and stop halfway through a word,
take a breath and continue on?
If I read that first sentence,
"Conscious control resides in the cerebral cortex,"
I didn't even take a breath in there.
But if I try doing this,
tell me if this sounds normal:
"Conscious con--(loud breath)
"trol resides in the (loud breath)
"cerebral cor--(loud breath) tex."
No, because it doesn't make sense.
You're breaking apart the word,
because you're not controlling the breathing
at a proper point.
What ends up happening now is
to read, to speak, to sing, any vocalization
you want to control your breathing
to make sure it sounds and makes sense.
The whole idea of holding your breath temporarily,
that varies from person to person.
Someone temporarily holding their breath
might be for only 20 or 30 seconds.
No problem.
Someone else that's a little more used to it,
maybe they're a swimmer,
might be able to hold their breath
for three, four, five minutes.
It all depends on lung capacity
and your ability to regulate your body activity.
But eventually your body's gonna say,
"Uh-uh, I'm done."
Your body will actually override
your ability to hold your breath
and say, "Start breathing."
Even if you try to hold your breath,
you'll hold it, hold it, hold it,
you might feel like it starts to hurt,
you might start to see a little black in the eyes.
But eventually your body automatically starts to breathe.
If you're stubborn,
you might even make yourself pass out first.
But the minute you pass out,
your body takes over and you start breathing.
Don't go trying this please,
(laughs) but the idea is your brain
is going to override your conscious thoughts.
The brain's looking out for your body.
It'll make sure you take a breath at some point.
So here we see the brain
and how it's connected down into the lungs.
First off, the respiratory cells near the respiratory center
respond to change in cerebrospinal fluid.
We're down in the brain stem, medulla oblongata.
If this happens because of an increase in carbon dioxide,
then receptor cells in the carotid aorta also respond.
But they're responding to a decrease in oxygen.
Even the higher centers in the cortex,
your conscious control,
you can consciously increase or decrease respiration.
That means there are three different ways
your body's monitoring and can control breathing.