Fox Chapter 16


TRANSPARENCY (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
(histology picture of cilia)
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)

Fig. 16.4
Trachea - rings of cartilage to hold tube open like a vacuum cleaner hose
2 bronchi
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.

Fig. 16.17
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.

Fig. 16.20
[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, obviously.
Recall, pressure lower in pulmonary circulation, and there is no regulation of flow to different areas as there is in systemic circulation.

Air Pressure

Fig. 16.18
Atmospheric pressure is measured in mm Hg

Fig. 16.19
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.

Fig. 16.22
Here is the cardio-respiratory system with blue blood (P O2=40, P CO2=46) and red blood (P O2=100, P CO2 = 40)

Lung volumes

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!


Fig. 16.7
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.

Fig. 16.14
Inspiration - pressure in lungs is lower than atmospheric, obviously, a word I seem to be using often, and expiration, pressure is higher.

Fig. 16.13
Muscles involved: intercostals and diaphragm mostly, and others as well.
Subtle differences for inspiration and expiration.

Fig. 16.11
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 center.

Fig. 16.24
Medulla rhythmicity center generates rhythm
Input from Pontine apneustic center (inspiration). Have you heard of sleep apnea?
Input from pontine pneumotaxic center counteracts inspiration.

Fig. 16.25
There are chemoreceptors in the aortic and carotid bodies, go to medulla in vagus (X) and glossopharyngeal (IX) respectively.

Fig. 16.26
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.

Fig. 16.28
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.

Fig. 16.28
Decreased breathing increases CO2 etc., resulting in a compensatory (there's that old negative feedback again) increase in breathing.

Fig. 16.27
Hyperventillation - blow off CO2 and desire to breathe less, can hold breath.

Transport of O2 and CO2

Fig. 16.31
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.

Fig. 16.32
Everyone should know that hemoglobin is composed of 2 alpha chains, 2 beta chains, and heme with iron in it.

Fig. 16.33
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 to tissues.

Fig. 16.37
Importantly, hemoglobin will offload oxygen to myoglobin based on the displacement.

(The same is true for the relation of adult hemoglobin and fetal hemoglobin.)

Fig. 16.38
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 acid).
then H2CO3 -> H+ and HCO3- (bicarbonate)
When this diffuses out of RBC, Cl- goes in (chloride shift)

Fig. 16.39
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? (answer both)

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 buffers

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 surfactant?
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?

residual volume

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 fluid?

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?

vital capacity

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 inspired air?

H2O, CO2

What are the pneumotaxic center and the apneustic center used to control?

respiratory rhythm

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 reason?

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?

residual volume

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?

760 mm

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 breathing?


What would alkaline cerebrospinal fluid do to breathing?

inhibit it

In pneumothorax, what compartment increases its pressure to that of the atmosphere?


In addition to containing heme, how would you describe the molecular structure of hemoglobin?

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?

residual volume

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 disease?

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 inspired air?

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?

intrapleural space

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 receptors

Why is the partial pressure of oxygen lower in alveoli lower than in the outside air?

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?

intrapleural space

Why would asbestos be more likely to stay in the lungs of smokers than of non-smokers?

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 control respiration?

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 alveoli?


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?

Tidal volume

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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