Lecture 17: The Work of Breathing Flashcards
The pressure of a gas is inversely proportional to its
volume
Decreased volume results in
increased pressure
Increased volume results in
decreased pressure
Pressure is proportional to the concentration because
of collisions of molecules with each other and with the container
Less collisions means
less pressure
More collisions means
more pressure
What drives the movement of gases?
a pressure gradient
Gas will more from _____ pressure to ________ pressure
high
low
Right before a breath, the pressure outside the body is _______ ______ the pressure inside the body so the air
equal to
does not flow
Describe the pressure gradient created when you inhale including how this affects the volume, the pressure and the flow of air
as you inhale
- volume increases
- pressure decreases
- air from the outside rushes into your lungs
Describe the pressure gradient created when you exhale including how this affects the volume, the pressure and the flow of air
as you exhale
- volume decreases
- pressure increases
- air from your lungs rushes outwards
What are the two opposing forces that must be overcome to take a breath?
- stiffness of the lungs
- resistance of the airways to the lungs
Describe why the stiffness of the lungs must be overcome?
The lungs don’t want to inflate naturally so there is resistance to stretching and accomodating the air
What two things determine the stiffness of the lungs?
their compliance and the surface tension which holds the lungs in place
What is compliance?
The ability to expand and accomodate an increased volume
Are the lungs compliant?
Yes
Give an example of lungs not being compliant and why?
What does this mean in terms of pressure and volume?
Pulmonary fibrosis
this means that there is scars formed from killed lungs cells and these are not as compliant (ie. it is more difficult to stretch lung to accomodate air)
This means that more pressure is required to reach a certain volume
Where does the surface tension that holds the lungs in place come from?
alveoli are lined with a fluid that exerts surface tension
Fluid in the alveoli and around the lungs does not allow the lungs to
expand
How do the lungs overcome the surface tension of the water in the alveoli?
alveoli produce surfactant which relives surface tension which allows them to expand during each breath
Why is there a frictional on the air in the conducting pathways?
There is resistance of the air through these pathways so there is a frictional force
What is the equation linking resistance to the radius?
R = 1/(r^4)
What determines the resistance of the airways?
the radius of the vessel
What is the role of the smooth muscle in the bronchioles?
bronchoconstrict
bronchodilate
What is the tidal volume (VT)?
the volume of air moved in and out during normal, quiet breath
What is the inspiratory reserve volume (IRV)?
the extra volume that can be breathed in with maximal inhalation
What is the expiratory reserve volume (ERV)?
the extra volume that can be breathed out with maximal exhalation
What is the residual volume?
The volume remaining in the lungs after maximal exhalation
What is the minimal volume?
volume remaining in the lungs if they collapsed
What is the vital capacity?
inspiratory reserve + expiratory reserve + tidal volume
ie. the total volume of air you can shift in and out of your lungs
What is the total lung capacity?
vital capacity + residual volume
ie. the volume in the lungs when you have filled them to the max
What is the inspiratory capacity?
inspiratory reserve + tidal volume
ie. total volume of air you can inspire from rest
What is the functional residual capacity?
expiratory reserve + residual volume
ie. the volume remaining in the lungs after normal exhalation
What does the FEV1 measure?
how much vital capacity comes out in one second
The FEV1 can discern between _______ and _________ issues
obstructive
restrictive
Obstructive issues are due to what?
Give two examples
resistance to airflow
eg asthma and bronchitis
Restrictive issues are due to what?
Give two examples
reduced lung capacity
eg. reduced lung compliance (fibrosis) and insufficient surfactant released
