In this course, students learn to recognize and to apply the basic concepts that govern integrated body function (as an intact organism) in the body's nine organ systems.
Exercise and Hypoxia
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Metabolic Pathways, Biology, Organ Systems, Medicine
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DH
Oct 11, 2016
I gained a deeper understanding and greater appreciation for how my body works. Thank you to the Teams at Duke and Coursera for making such a wide body of information available to the motivated.
WL
Apr 01, 2016
Lectures are very concise. This course can help you grasp the most important core concepts and key woking mechanisms of human physiology. But I don't know why it do not have the immune system.
从本节课中
Respiratory System
We hope that you are enjoying the course! This module considers the respiratory system. In these lessons, we explore topics such as how we get air into our lungs, the role of airway resistance in ventilation, the transport of oxygen and carbon dioxide between the lungs and tissues, and the regulation of breathing. There are a couple of demonstrations of lung function in the videos! The things to do this week are to watch the 8 videos, to answer the in-video questions, to read the notes, and to complete the Respiratory System problem set. We suggest that you read the notes, watch the videos, and answer the in-video questions before you start on the problem sets, which are not graded. Take a deep breath and have fun with it!
教学方
Jennifer Carbrey
Assistant Research Professor
Emma Jakoi
Associate Research Professor
Welcome back, this is our last video about the respiratory system, we're just
going to consider some disturbances in oxygen and proton balance.
We're going to consider what happens when we
exercise and then we're going to consider hypoxia, when.
The amount of oxygen is lower in the blood.
So we have,
let's consider first what happens during exercise.
Where with this series of graphs we have what
is going on when we're at rest versus vigorous exercise.
And as we move from being more and more active after we've been resting.
So let's say that we start doing low
intensity exercise, and then we do moderate exercise.
Then the minute ventilation is going to increase.
Okay linearly and that makes sense and as a result
in that linear, linear increase in minute ventilation then
the oxygen is, amount of oxygen is going to stay stable
and the amount of CO2 is going to basically stay stable as well as.
Proton
concentration.
So we're matching our needs by increasing ventilation.
Then, as we're getting close to maximal exercise and we're getting more and more
vigorous, that's when we start to see a change, where now all of a sudden.
Minute ventilation is increasing in a non linear fashion.
And it is doing that because we see the arterial ph or arterial
proton concentration is also increasing. In a non-linear fashion.
And so this increase in minute ventilation is in, in
response to an increase in protons because we're forming lactic acid.
So basically, we're getting into a state of metabolic acidosis.
Where we've got an increase in protons, which is going to
cause an increase in ventilation, so now we're basically hyperventilating.
And now our PO, PCO2 is decreasing.
Okay?
So that's something that is going to happen during exercise, and it's,
particularly during vigorous exercise. The other thing to think about is the
change in minute ventilation, as we're doing exercise,
particularly, at the very beginning and at the very end - where if
you're a trained individual, your body learns
to anticipate exercise. And so, what we can get.
Is this feed forward process of the fact that the body knows that you're about
to do exercise.
So that as soon as you start, ventilation increases more than it actually needs to.
So we saw in the last slide that it just kind of increased linearly as you.
Increased your intensity. Here we're having this large jump at
step one where we have this instantaneous increase in minute
ventilation and anticipation to kind of get a jump
start on ventilation. Then as we keep going, it's going to.
Gradually keep increasing until we get to the end
where we will have a pretty rapid drop in ventilation,
but it's not back down to baseline. It's well
above baseline, and then it will slowly decrease down to baseline.
And so you're continuing to breathe.
More heavily than you need to considering what you are doing.
You all know this.
If you sprint for a long distance and then stop you are now at
that point maybe just walking or standing but you are still breathing very rapidly.
And so that's occurring
so that you can.
Get every all your systems back to base line.
So you're trying to remove what's called the oxygen debt.
Because of your exercise you have depleted
the stores of. Oxygen-saturated myoglobin.
So this is going to be a molecule that's very similar to hemoglobin that's
being, that's in the muscle, that can store oxygen in the muscle.
So after you exercise, those stores are going to be depleted.
So you're trying to keep that extra oxygen coming in to.
- load up myoglobin again.
And then, we remember, in muscle, we also talked about creatine phosphate, which
needs to be converted back, so that it can be used again.
So, those are going
into, over the next several minutes, be regenerated through this increase in
oxygen uptake. And then, we also might have lactic acid.
Around, so there, that might also be an aspect of the
increased ventilation is also correcting an acid base imbalance as well.
Okay, so we've talked about exercise, now we're going to finish up talking about
hypoxia, which is going to be a deficiency of oxygen in the tissues for some reason.
And there can be different types of hypoxia.
So we can talk about hypoxic hypoxia, which is a little redundant, when
what the problem is that we have low oxygen in the blood.
That's the issue. That is
separate from having hypoxia because we're anemic,
because we, for instance, don't have enough red blood cells, meaning
that the Pa, the PaO2, the arterial pressure of
oxygen, is just fine, but we have low oxygen content.
Because, remember, hemoglobin's going to represent 80.
98 to 99%
of the oxygen in the blood. We can also have issues where the
amount of oxygen in the blood is just fine, but we have low oxygen delivery.
So for instance, if we had a blood clot the prevented blood flow.
Would, that would be ischemic hypoxia.
Or, if you put a tourniquet on your arm, then your arm is going to have ischemic
hypoxia because you don't have blood flow.
But the bloo-, the amount of oxygen in the blood is just fine.
Then there's histotoxic hypoxia, which is when there is oxygen in the blood.
And there is delivery to the tissue, but if you have something like cyanide present
that prevents the use of the oxygen, then it's,
that would be histotoxic hypoxia.
It's basically like there isn't oxygen there.
- because you're not able to use it.
In the case of cyanide, in to recept, to receive electrons in
electron transfer chains, because that is what is disrupted by cyanide.
So, let's talk a little bit more about
some causes of hypoxic hypoxia, things that can.
Prevent you from having enough oxygen in the blood.
In, and more specifically, a low arterial pressure of oxygen, so
one's going to be hypoventilation, if for some reason you are not breathing enough.
The other could be diffusion impairment,
which we've talked about a little bit. Where you might have normal alveolar
pressure of oxygen but then if you have liquid, or
mucus, or connective tissue that is preventing diffusion
then that can easily affect the pressure of oxygen in the blood.
And then we can have ventilation perfusion inequality.
And we've talked about how we all, even in a normal lung, have some V-Q mismatch,
but then how we can have some other pathological issues
or other issues that can cause an increase in that ventilation-perfusion mismatch.
Another thing that can cause hypoxic hypoxia is sleep apnea,
which is a increasing problem where,
when you sleep, you are going to have a reduced
frequency of breathing. And you're
going to have a decreased
flow rate when you breathe in, so you're going to be breathing left less often, and
less, you're going to be taking in less oxygen as well, or less.
Air and so that means that your
minute ventilation is going to basically decrease.
In addition, skeletal muscle is going to relax.
You're going to have reduced tone in your skeletal muscle and so that
can cause. A collapsed of the upper airways,
like the pharynx and larynx in the mouth and throat.
And then also of your tongue, which can cause an occlusion of the airways.
So it, that can cause you to make sounds
such as snoring, but then, if you have a complete.
Occlusion of the airway.
And that is what we refer to as sleep apnea.
Where you can stop breathing for 30-60
seconds and then basically you will
wake up very often and then gasp for air.
And the kind of scary thing about this is that often when you
have sleep apnea, it's not that you're doing this once a
night, that you're stopping breathing for 30 to 60 seconds.
It can be many, many times just in an hour.
So, it's obviously, not good to be oxy,
oxygen deprived, but then, also, not to, not
good to be sleep-deprived, because you're really basically
waking up at least some, at some level.
It might not be really at a conscious level, in order to open those airways
back up.
So, we have a question of what's going to stimulate.
You to wake up and to fix your breathing and that's going to be.
We know that you are most sensitive to the arterial CO2 pressure and so that's what
is going to activate those central chemo receptors
to cause you to make sure that you breath.
And really the best treatment for this.
Sometimes if it's based on the architecture of the nose or
the throat then you can have surgery to fix this problem
but there is a machine called a C Pat machine that provides
continuous positive airway pressure so it's a mask that people wear.
And then that provides
a continuous flow of air that's per just enough to keep
those airways open at all times so that people breathe
at all, all times and that they don't wake up because of a lack of breathing.
So, we've talked about exercise.
That's going to be a time when we all are going to have to increase our ventilation,
and, when we really get into the intense exercise,
that's when we can start to have metabolic acidosis.
And so, that.
Is going to cause us to basically hyperventilate,
which means CO2 will fall, but then
that will reduce the amount of protons
to try to compensate for the metabolic acidosis.
And then we talked about sleep and how it's going to cause
us to breathe less. And also cause the airway muscles to
relax which can cause obstruction, either complete,
causing sleep apnea, or partial, which can lead to noisy sleeping and snoring.
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