Fox Chapter 16
(review from introductory course)
Summarizes much of what will be said below, including the next transparency.
Nasal - moisture (smell) sniffing
Pharynx - larynx
Vocal cords larynx (laryngitis) "voice box"
Equal time to creationism : "Adam's apple"
Further down cilia sweep mucus, bacteria, dust up
Cilia sweep from pharynx to esophagus (where you can swallow "crud")
Smoking paralyses ciliary sweep (more crud, less sweeping, famously asbestos
is worse in smokers)
Trachea - rings of cartilage to hold tube open like a vacuum cleaner hose
Inflammation of the bronchi is called bronchitis.
Review chapter 9 material and note that sympathetic n.s. causes relaxation
of smooth muscle (opening passageways) in lungs and parasympathetic n.s.
constricts them (closing passageaways). The purpose is to regulate air flow.
Asthma caused by mast cells and eosinophils secreting leucotrienes, bronchioconstriction,
use epinephrine to stimulate beta 2 receptors (note heart has beta 1 receptors).
Epinephrine was in inhalers. Terbutaline is an anti beta 2 drug. Singulair
is an antileukotriene. Because inspiration helps to open the bronchioles,
breathing out (this is counterintuitive) is most difficult.
Alveoli 600 million in human 50 x skin area
Here is a picture
from our histology course (like Fig. 16.18) showing how thin the cell layers
of alveoli are.
Emphysema - alveoli merge, often results from smoking, increased muscular
effort in breathing- smoetimes they have a hunch back from using back to
help breathe. These are the people older than they look pulling a dolly
of oxygen around with them.
[much like part of the figure from introductory course]
Air sacs (alveoli) are close to capillaries.
Note, red vs blue for arteriole vs venule is reversed for pulmonary circulation,
Recall, pressure lower in pulmonary circulation, and there is no regulation
of flow to different areas as there is in systemic circulation.
Atmospheric pressure is measured in mm Hg
Partial pressures of inspired air and alveolar air
Pressure relates to gas exchange.
In alveoli, H2O & CO2 higher and O2 lower for obvious reasons that we
will chat about.
Here is the cardio-respiratory system with blue blood (P O2=40, P CO2=46)
and red blood (P O2=100, P CO2 = 40)
Fig. 16.15 also here
Breathing in and out normally is called tidal breathing, volume about half
a liter. There is an expiratory reserve, over a liter, and an inspiratory
reserve, maybe 3 l. From the top of inspiration to the bottom of expiration
is vital capacity. Even after you empty your lungs as much as possible there
is a residual volume, over one liter.
A simple spirometer
with a dispo tube to breathe into can be used cheaply to measure vital capacity,
tidal volume and expiratory reserve.
A summary point: not all the air exchanges!
Pleura, very slippery, and pleural cavity, slightly lower than atmospheric
pressure, are important.
Pleurisy is inflammation of pleura, breathing is painful.
The low pleural pressure keeps the lungs open unless an injury lets air
into cavity, "pneumothorax," collapses lung.
Inspiration - pressure in lungs is lower than atmospheric, obviously, a
word I seem to be using often, and expiration, pressure is higher.
Muscles involved: intercostals and diaphragm mostly, and others as well.
Subtle differences for inspiration and expiration.
Water's surface tension would tend to collapse (close) alveoli. Type II
alveolar cells secrete surfactant (surface active agent), phosphatidylcholine
plus phosphatidylglycerol, that decreases surface tension. RDS (respiratory
distress syndrome) aflicts premature babies since surfactant production
does not start until late.
Cystic fibrosis is from mutation in CFTR (cystic fibrosis transmembrane
regulator), a chloride channel, results in viscous mucus.
Control of ventillation
Introduction: The receptors that are sensitive to changes in the concentrations
of CO2 and H+ are located within the arterial system and the medulla of
the brain. Excitation of these receptors trigger neural reflexes which alter
the respiratory rate and depth. Additionally, other parts of the nervous
system influence the basic ventilation pattern established by the respiratory
Medulla rhythmicity center generates rhythm
Input from Pontine apneustic center (inspiration). Have you heard of sleep
Input from pontine pneumotaxic center counteracts inspiration.
There are chemoreceptors in the aortic and carotid bodies, go to medulla
in vagus (X) and glossopharyngeal (IX) respectively.
This diagram adds a few items:
(1) Cerebral cortex over-rides. The funny thing about this information is
that it is hard for you to think about how you breathe without you changinging
how you breathe.
(2) There are important chemoreceptors in the medulla.
Without the buffers that blood has, cerebrospinal fluid (CSF) on the other
side of the blood brain barrier has CO2 and H2O -> carbonic acid generating
H+ that affects receptors.
Summary. A common misconception is that variation in the O2 levels within
the system cause changes in the ventilation rate. Actually, the O2 concentration,
under normal conditions, has little to do with the determination of respiratory
rate. The critical determining factor is the level of CO2 and/or the level
of free protons circulating in the blood. For example, an increase in CO2
or H+ levels will induce changes which result in an acceleration of the
ventilation rate and volume until these levels return to the normal range.
Conversely, conditions associated with alkalosis and lower than normal CO2
levels depress the ventilation rate.
CO2 and CSF acidity are stimuli for breathing, and that is why oxygen given
to patients has CO2 in it.
Decreased breathing increases CO2 etc., resulting in a compensatory (there's
that old negative feedback again) increase in breathing.
Hyperventillation - blow off CO2 and desire to breathe less, can hold breath.
Transport of O2 and CO2
The trouble is that oxygen does not dissolve well in water, 66 x as much
oxygen is in blood, with its hemoglobin, than in plasma.
Everyone should know that hemoglobin is composed of 2 alpha chains, 2 beta
chains, and heme with iron in it.
Here is the famous oxyhemoglobin dissociation curve, % oxyhemoglobin saturation
as a function of P O2 (mmHg).
By comparing arteries with veins, we can see how much oxygen is offloaded
Importantly, hemoglobin will offload oxygen to myoglobin based on the displacement.
(The same is true for the relation of adult hemoglobin and fetal hemoglobin.)
From tissue to blood:
CO2 transported as bicarbonate, bound to hemoglobin, and dissolved in blood
CO2 dissolves better than O2 in water
Red blood cells CO2 + H2) -> (carbonic anhydrase)-> H2CO3 (carbonic
then H2CO3 -> H+ and HCO3- (bicarbonate)
When this diffuses out of RBC, Cl- goes in (chloride shift)
The reverse happens to put CO2 from blood to alveoli.
Exam questions from 2004 - 2011 relating to this outline
What would stimulation of beta-2 adrenergic receptors do to the air
flow in trachea and bronchi?
open airways, increase air flow
Answer either (1) why oxygen in the air we breathe has a partial pressure
lower than 760 mm Hg, or (2) why the oxygen in alveoli has a lower partial
pressure than the oxygen than the air that we breathe.
only about 20 % of the air we breath is oxygen, then, the value is further
lowered by the high carbon dioxide and water in the lungs
The total lung capacity equals the tidal volume plus (what)? Hint, there
should be several components to your answer.
inspiratory and expiratory reserves plus residual volume
A healthy individual has an injury resulting in pneumothorax. In what direction?
and how much (approximately)? does the pressure in the pleural cavity change?
it goes up a tiny bit about 5 mmHg
What specialization in the trachea powers the mucus elevator?
Epinephrine would help a person having an asthma attack. What completely
different approach could be used, in this case to control inflammation?
antileukotriene like Singulaire
Name one component that separates air in the alveloi from red blood cells.
type I alveolar cell, basal lamina, endothelial cell
The partial pressure of carbon dioxide in the pulmonary vein is 40 mm Hg.
What is the partial pressure of carbon dioxide in the systemic arteries?
duh! there was no gas exchange between the two
"Water's surface tension would tend to collapse (close) alveoli."
Answer either (1) How does physiology take care of this problem? or (2)
People with what condition have a real problem because of this?
surfactant, premature babies
"The buffering capacity of blood keeps high carbon dioxide from changing
pH much." Then how does physiology improve on this sensitivity in chemoreceptors
in the medulla?
on that side of the blood brain barrier, the cerebrospinal fluid has no
The partial pressure of carbon dioxide in the pulmonary vein is 40 mm Hg.
How would hyperventillation affect this?
cut it in half
Why do people with emphysema need to breathe more?
With fewer alveoli, there is less area for gas exchaqnge
In what way is the coating of water in the alveoli different with vs. without
With-it has lower surface tension than without
For cystic fibrosis, (answer one of these) (1) A gene, mutated in cystic
fibrosis, codes for what? (2) What are the symptoms? Or (3) How does the
parent treat those symptoms on a daily basis?
CFTR, a chloride channel
What happens to ventilation when pH goes down in the cerebrospinal fluid
(CSF) of the medulla oblongata at the confluence of integrating inputs from
aortic and carotid bodies, the pneumotaxic center and the apneustic center?
More acidity implies more carbon dioxide, so you breathe harder
Pick one: (1) A drug that specifically affects beta-2 adrenergic receptors
(terbutaline), or (2) a drug that blocks leukotriene action (Singulair).
What is the specific action that would help in asthma?
1 open airways by mimicing adrenalin or the sympathetic nervous system,
2 decrease inflammation
The partial pressure for oxygen in the atmosphere is atmospheric pressure
times the fraction of the atmosphere that is oxygen. What are the major
reasons that the partial pressure for oxygen in the alveoli is much lower?
there are higher proportions of water vapor and carbon dioxide
You have a subject and a spirometer. What value, a portion of total lung
capacity, cannot be obtained?
Give either the approximate number or the value relative to atmospheric
pressure of the intraplural during inhalation.
book says 754 mm Hg, the point is that it is slightly less than lungs which
are slightly less than atmospheric
Why does a premature baby have trouble breathing?
type 2 alveolar cells mature late and without surfactant, water pressure
impedes alveolar opening
Where, other than the medulla oblongata, are chemoreceptors located that
feed by nerves to the respiratory control centers?
aortic and carotid bodies
Relative to curve where % oxygen saturation is plotted as a function of
partial pressure for oxygen for adult hemoglobin, how would you place the
curve for fetal hemoglobin?
fetal oxyhemoglobin dissociation curve is to the left of the adult
Why does chloride come out of red blood cells in the lungs?
so bicarbonate can come in for the generation of carbon dioxide to be exhaled
If you hyperventillated, what would become of the pH of the cerebrospinal
less CO2, pH goes up
What is the biological word for the Adam's apple?
Expiratory reserve plus inspiratory reserve plus tidal volume equals what?
What is the chloride shift?
Cl- goes into erythrocyte when HCO3- comes out and vice versa
What is the intrapleural pressure? (I want an approximate value.)
slightly less than atmospheric
What two gasses have much higher partial pressure in alveolar air than in
What are the pneumotaxic center and the apneustic center used to control?
Cystic fibrosis is a channel for what ion?
An asthma spray would contain an agonist for what naturally ocurring neurotransmitter?
Where are the brain centers that control breathing?
medulla and pons area
The abscissa (X-axis) of the oxyhemoglobin dissociation curve is partial
pressure of O2 in mm Hg. What is plotted on the ordinate (Y-axis)?
% saturation (with O2) of hemoglobin
What compound (related to but not the same as prostaglandins) constricts
bronchial smooth muscle (blocked by Singulair)?
One reason that the partial pressure of CO2 is higher in alveoli than in
the atmosphere is that cells generate CO2 (as waste). What is the other
not all the air in the lungs is exchanged by breathing
Partial pressures for CO2 and O2 are almost equal in alveolar air and pulmonary
veins. For which gas is there a greater difference between alveolar air
and pulmonary arteries?
Which component of lung volume cannot be measured with a spirometer?
What is the naturally ocurring hormone for beta-2 receptors in bronchi?
What is the highest level that mercury would rise in a glass tube with a
vacuum at the top?
Respiratory distress syndrome in premature infants results from the lack
of what molecule?
surfactant (phosphatidyl choline)
Where do chemoreceptors in aortic and carotid bodies feed to to control
What would alkaline cerebrospinal fluid do to breathing?
In pneumothorax, what compartment increases its pressure to that of the
In addition to containing heme, how would you describe the molecular structure
2 alpha and 2 beta protein chains
A figure in your text indicated that one place was responsible for "automatic
breathing," while I cautioned you that this was very different from
automaticity in the heart. What is this place that generates automatic breathing?
Bicarbonate in plasma helps in CO2 transport. It is made with the help of
what enzyme in what cell?
carbonic anhydrase in red blood cell
What would O2 on mother's hemoglobin do when it gets near fetus hemoglobin
in the placenta?
offload to fetal
When is the pressure in the alveoli slightly higher than atmospheric?
The total lung capacity is tidal volume + inspiratory reserve + expiratory
reserve + what?
What is the significance of the value 760 mm Hg?
atmospheric pressure at sea level
Why does a mutant chloride (Cl-) channel (CFTR specifically) lead to lung
poor ion transport -> poor water transpord -> viscous mucous
For the sake of CO2 transport, where is bicarbonate (HCO3-) made and where
is it carried?
made in RBC, carried in plasma
Why is the partial pressure for alveolar H2O much higher than for H2O in
air is humidified, usually in nasal passageways
What common effect (though to different extents) do leukotrienes and the
parasympathetic nervous system have on bronchioles?
decrease air flow
What does emphysema do to the number of alveoli?
decrease since adjacent ones merge
Why is the partial pressure for CO2 higher in the pulmonary artery than
in the alveoli?
pulmonary artery carries CO2 offloaded by tissue respiration
Although phosphatidylcholine is best known as a membrane phospholipids,
it also has a special function in the lungs. What is this function.
component of surfactant, decrease surface tension of water
You breathe in and out your vital capacity a dozen times in rapid succession.
What is this called and why would your urge to breathe be decreased for
the next minute?
hyperventillation, by blowing off CO2, less H+ in medulla
A stab wound to the chest can lead to the collapse of a lung because what
compartment would increase its pressure to atmospheric pressure?
What is the important nerve connecting the heart and the brain that carries
chemoreceptive signals from the aortic bodies?
vagus (10th cranial)
Why would you want to inhale adrenalin? (Your answer can address pathology,
cells or molecules.)
asthma, relax smooth muscle, open bronchial airways, activate beta 2 adrenergic
Why is the partial pressure of oxygen lower in alveoli lower than in the
because water vapor and carbon dioxide fractions are so much higher
A slight increase in pressure (where?) would allow the lung to collapse
if there were a stab wound to the chest?
Why would asbestos be more likely to stay in the lungs of smokers than of
smoking paralyses cilia
How does intrapleural pressure relate to alveolar pressure (at rest, breathing
in and breathing out)?
a little lower in all cases
Why would it take more effort than a premature baby could muster to breathe?
there is no surfactant to decrease water tension
Name one of the two nerves that carry chemosensory input to the brain to
glossopharyngial (9th) and vagus (10th)
Why is it so useful to monitor pH of the cerebrospinal fluid to report the
need to breathe?
carbon dioxide would make pH go down
What does the sympathetic nervous system do in bronchi? (Your answer can
either be at the level of the cellular response or of the passageway function.)
beta 2 receptors relax smooth muscle open airway
What could you do to lower the partial pressure of carbon dioxide in your
Give a ballpark figure for the partial pressure of carbon dioxide in the
arteries for normal breathing and for hyperventilation.
40 mm Hg, less if hyperventillate
Why does chloride need to go in and out of red blood cells?
to move bicarbonate to plasma where there is room to carry it
Why wouldn't you expect inhibitors of prostaglandin synthesis to help with
inflammation in asthma?
Leukotrienes, not prostaglandins
Total lung capacity minus expiratory reserve minus inspiratory reserve minus
residual volume equals what?
What happens to the pressure in what compartment to cause the lung to collapse?
Intrapleural becomes equal to atmospheric
Other than the medulla (of the brain), where are there chemoreceptors to
control ventilation? (or, if you prefer, tell me how they feed to the brain.)
aortic and carotid bodies
What is the purpose of cilia in the trachea?
to sweep gunk captured in mucus up to where it gets swallowed
How would epinephrine in an inhaler affect breathing? (Your answer could
apply to molecular type of the receptor or to affect on the airway.)
beta 2, dilate (open) bronchioles
What is it that would make mercury go up 760 mm in a glass tube?
atmospheric pressure (not "suction")
Give at least 2 reasons oxygen's partial pressure is so much lower in alveoli
than in the atmosphere.
our of 3: (1) there is so much CO2 in alveoli, (2) there is so much H2O
in alveopi, (3) not all air is exchanged each breath
The partial pressure for carbon dioxide in the pulmonary artery is 46. What
is it in the pulmonary vein?
lower, but not that much lower (40)
Why would they put premature babies in high oxygen?
lack of surfactant makes breathing difficult
Relative to carbon dioxide, how much oxygen is carried in the plasma?
O2 is way less soluable in water than CO2 (the figure clearly showed 10%
for CO2, another figure implied about 1.5 % for O2)
"Most bicarbonate is carried in the plasma." But it was made in
the erythrocyte. What trickery was used to move it to the plasma?
exchange with Cl-
"Mucus elevator." Relate to the conventional wisdom about the
interaction of asbestos and smoking.
smoking paralyses cilia so asbestos gets stuck in lungs worse
What would the sympathetic nervous system do to the air passageway opening?
The partial pressure of O2 in the atmosphere is 159 mm Hg. Give a reason
it is much lower in the alveoli.
lowered b/c water and CO2 are high
You are studying the respirometer record of a patient. What is the one volume
you cannot ascertain from this record?
Why might a lung collapse from a piercing stab wound to the chest?
intrapleural pressure becomes atmospheric pressure
Why does surfactant make breathing easier?
decreases surface tensiol
What information is carried from the aortic and carotid bodies to the brain
to control breathing?
How does the ionization of carbonic acid into H+ and HCO3- in the red blood
cell greatly increase the amount of carbon dioxide that can be transported?
then bicarbonate can be sent to the large volume of the plasma
Why would you expect that aspirin and ibuprofen would not help you with
inflammation in the trachea and bronchi?
caused by leukotrienes not prostaglandins
Why would breathing be difficult in a premature infant?
surfactant secreting cells are not mature yet
What must happen to compensate for bicarbonate moving from the red blood
cell to the plasma?
chloride must move in
Hyperventilation typically halves the partial pressure of carbon dioxide
in the lungs to a value of about (what?).
20 mm Hg
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