Lecture 34: How do we breathe?
• Boyle’s Law: Air Pressure – Volume
• Effect of temperature on air pressure
• Atmospheric Pressure & Altitude
• Air Flow Equation
• Alveolar pressure & volume
• Muscles use in Ventilation
• Alveolar pressure in inhalation/exhalation
• Expiratory Peak Flow & Resistance
• Effects of sex, size & age
• Vital Capacity Volumes
• Effect of Dead Air & Residual Volumes
• Maximum VC (age, sex)
• Exercise Effects (immediate vs. long term)
• Respiration rate & tidal volume
https://www.youtube.com/watch?v=3hwbxW7sRvk
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Pleural
membranes
Diaphragm
Dr. Casey Self, Biol. 118, Autumn 2016
1
Explain the relationship between air
pressure & volume & air pressure & temp.
Pressure ~ 1/volume
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http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/gaslaw/boyles_law.html
2
We’ll use mmHg units to measure air pressure.
Why is air pressure higher at sea level?
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3
Use this equation to explain how air moves in/out:
Air Flow = (Palveoli - Patmosphere )/Resistance
Increase volume  decrease pres.
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Decrease volume  increase pres.
4
Explain alveolar pressure & air flow changes in ventilation.
(Palveoli -Patmosphere )
Air Flow = (Palveoli - Patmosphere )/Resistance
Inhale
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Exhale
http://droualb.faculty.mjc.edu/Course%20Materials/Physiology%20101/Chapt
er%20Notes/Fall%202011/chapter_16%20Fall%202011.htm
5
Why do peak expiratory flow values differ
between men & women and change with age?
Air Flow ~ Pressure gradient * (radius4)
How would asthma
affect peak flow?
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http://www.admit-online.info/en/background-information-respiration/pathophysiology/lung-capacities/
6
Vital capacity = TV + ERV + IRV. What does it mean?
http://emedicine.medscape.com/article/303239-overview
Dead Air
Residual Volume
TV = tidal volume
ERV = expiratory reserve volume
IRV = inspiratory reserve volume
Tidal Volume
Inspiratory
Reserve
Volume
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Expiratory
Reserve
Volume
7
Explain why vital capacity changes with aerobic
exercise & age. Why does it differ between sexes?
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8
Which muscles aid ventilation? How would airway
resistance alter the cost of breathing?
Inhale = Inspire
Sternocleidomastoids
Scalenes
Internal
Intercostals
External
Intercostals
Diaphragm
Abdominals
Exhale
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https://online.science.psu.edu/biol141_wc/node/7590
9
How does the depth of a breath alter the
amount of fresh air entering lungs?
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http://droualb.faculty.mjc.edu/Course%20Materials/Physiology%20101/Ch
apter%20Notes/Fall%202011/chapter_16%20Fall%202011.htm
10
Why can’t residual volume ever be exhaled?
Respiratory Minute Volume (RMV)(L/min) = Respiratory Rate * Tidal Volume
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http://ptexphys.utorontoeit.com/respiratory-physiology/regulation-of-ventilation-during-exercise/
11
How do respiration rate & “tidal volume”
change with exercise?
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http://ptexphys.utorontoeit.com/respiratory-physiology/regulation-of-ventilation-during-exercise/
12
Things to understand or review:
1. Describe how these factors affect air pressure: temperature, elevation & volume. Graph
these relationships, with the factors on the X-axis & air pressure on the Y-axis.
2. Write the equation for air flow. Why is air flow called bulk flow? Does air flow “up” or
“down” a pressure gradient? Why is the radius of an airway the most important factor
controlling resistance to air flow? Graph the relationship between radius of an airway on the
X-axis &”relative” air flow on the Y-axis.
3. Calculate the direction & relative volume of air flow if you are given Patmosphere & Palveoli.
Explain why the flow of air stops at the end of inhalation or exhalation. Explain how you can
take larger breaths.
4. What events/substances can dilate your airways? What can constrict your airways? Predict
which part of the airways has the biggest effect on airflow. How does asthma alter peak
flow? Explain how & why peak flow changes with age, sex or exercise?
5. Calculate vital capacity given information on the various lung volumes. Which volumes are
used during exercise? Why isn’t residual volume every exhaled? How does does dead air
volume (in the airways) affect the gases in the lungs? Explain how & why vital capacity
varies with age, sex. Predict the effect of exercise on vital capacity.
6. Explain the changes in respiration rate & ventilation volumes with exercise.
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13
Why does increased airway resistance
make it harder to breathe?
Air Flow = (Patm - Palv)/Resistance
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14