Chapter 48 Flashcards
What is the major physiological challenge facing all multicellular animals?
obtaining sufficient O2 and getting rid of excess CO2
Which animal is the respiratory champion?
elephant seals, which can hold their breath for over 2 hours
Invertebrates display a wide variety of respiratory organs, including
the epithelium; tracheae; gills
Which vertebrates use gills?
fish; larval amphibians
What do adult amphibians use to respire?
skin; other epithelia (either supplementary or primary external respiratory organ)
Generally speaking, which animals have lungs?
adult amphibians; reptiles; birds; mammals
(T/F) Lungs are only present in terrestrial animals.
False, lungs are also present in aquatic animals
What is necessary for plasma membranes to be stable?
Plasma membranes must be surrounded by water to be stable
The external environment in gas exchange is always
aqueous (even in terrestrial animals, since a fluid lines the respiratory organs)
What drives the diffusion of gas into the fluid layer surrounding respiratory organs in vertebrates?
passive diffusion - concentration difference between O2 and CO2
For dissolved gases, concentration is usually expressed in
partial pressure
What law governs the relationship of the rate of diffusion between two regions?
Fick’s Law of Diffusion
What does Fick’s Law of Diffusion say?
the rate of diffusion (R) is directly proportional to the pressure difference (Δp) between the two sides of the membrane and the area (A) over which the diffusion occurs
What is the relationship between R and d in Fick’s Law?
R is inversely proportional to the distance (d)
Write out Fick’s Law.
write out pg. 1002
How can R in Fick’s Law be optimized?
increase area; decrease distance; increase concentration difference
What is the maximum diffusion distance for the levels of oxygen needed by cellular respiration?
0.5 mm
What are the consequences for the maximum diffusion distance of O2 at 0.5 mm?
bacteria are small enough, but multicellular animals require structural adaptations to enhance gas exchange
Do invertebrates have specialized respiratory organs?
No, they lack specialized respiratory organs
How do invertebrates increase the oxygen concentration difference?
some create a water current that continuously replaces the water over respiratory surfaces
Which invertebrates possess respiratory organs?
mollusks; arthropods; echinoderms
Give two ways in which respiratory organs maximize Fick’s law.
bring the external environment closer to the internal fluid to minimize distance; maximizes surface area
Which factor is affected by continuously beating cilia?
concentration difference (because beating cilia continuously replenishes water/O2)
What are gills?
specialized extensions of tissue that project into water
What is the simplest form of gills?
papillae of echinoderms
What is the most complex form of gills?
highly convoluted gills of fish
What is the primary advantage of gills in terms of respiration?
enables aquatic organisms to extract far more oxygen from water than would be possible from just body surface
External gills are found in what organisms?
fish; amphibian larvae
Give examples of organisms with external gills.
larvae of many fish/amphibians; axolotl (amphibian)
What is unusual about the axolotl?
retains larval features throughout its life
What are the disadvantages of external gills?
must be constantly moved to ensure contact w/ fresh water w/ high O2; significant resistance to movement; easily damaged
What are branchial chambers?
structures that provide a means of pumping water past stationary gills
What is the composition of air?
21% oxygen; 78% nitrogen; <1% CO2 + other gases
Describe the nature of nitrogen gas in air.
inert; not part of respiratory processes
What is atmospheric pressure?
pressure exerted by the atmosphere on the body surfaces of animals
What is 1 kPa in mm Hg?
1 kPa = 7.5 mm Hg
What is sea level in terms of mm Hg?
760 mm Hg
(T/F) Atmospheric percentiles change as altitude changes.
False, atmospheric percentiles do NOT change with changing altitudes.
Compare the rate of oxygen diffusion into blood at higher and lower elevations.
At higher elevations, rate is lower; at lower elevations, rate is higher
Are most gases able to dissolve in water?
No, most gases dissolve poorly in water
What are three factors that increase the solubility of gases in water?
higher pressure; cold water; lack of other solutes
(T/F) The respiratory system is independent of the vascular system.
True, the respiratory system is independent of the vascular system.
What is the minimum number of cell layers for entering the bloodstream?
2
What is the branchial chamber in mollusks?
mantle cavity
Describe the structure of the mantle cavity.
opens to the outside; contains the gills
How does the mantle cavity function as a branchial chamber?
contraction of the muscular wall of the mantle cavity draws in water through inhalant siphon and expels through exhalant siphon
Where is the branchial chamber located in crustaceans?
between the bulk of the body and the hard exoskeleton of the animal
Describe the structure of the branchial chamber in crustaceans.
opens to the surface beneath a limb; contains gills
How does the branchial chamber in crustaceans function?
movement of limb draws water through branchial chambers which creates current over gills
Branchial chambers are found in which types of organisms?
mollusks; crustaceans
Where are the gills of bony fishes located?
between oral cavity and opercular cavity
What is another name for the oral cavity found in bony fishes?
buccal (mouth) cavity
What purpose do the buccal and opercular cavities serve in respiration in bony fishes?
they are pumps that expand alternately to move water into mouth, through gills, and out of body via open opercula
Which fish have immobile opercula and why?
tuna, because they swim continuously
How do fish with immobile opercula breathe?
swim with mouths partly open, which constantly forces water over gills
What is ram ventilation?
bony fishes with immobile opercula swim with mouths partly open, which constantly forces water over gills
What is the remora?
bony fish that rides piggyback on sharks
How does the remora breathe?
when hitched to a shark, uses ram ventilation; uses normal pumping action when shark stops swimming
How many gill arches can be found on each side of the fish’s head?
between 3 and 7 gill arches
Each gill arch is composed of
two rows of gill filaments
Each gill filament is composed of
lamellae, which project out into the flow of water
How do blood and water flow with respect to lamellae?
Blood flows in the opposite direction of water flow
What is countercurrent exchange?
blood and water flow in opposite directions in lamellae to maximize oxygenation
How does countercurrent exchange maximize oxygenation in terms of Fick’s law?
it maintains a positive oxygen gradient along the entire pathway for diffusion, which increases Δp in Fick’s law
If blood and water flowed in the same direction, it would be called
concurrent flow
Why isn’t concurrent flow a good idea?
because the concentration difference would decrease and there would eventually be no further net diffusion
What is the most efficient respiratory organ?
gills, because of countercurrent exchange
What is cutaneous respiration?
process of exchanging oxygen and CO2 across skin
Describe cutaneous respiration in amphibians.
supplements (sometimes replaces) action of the lungs
Can animals respire exclusively through cutaneous respiration?
Yes, some terrestrial amphibians such as plethodontid salamanders use cutaneous respiration exclusively
Which animals use cutaneous respiration?
amphibians; reptiles (like turtles)
Why do terrestrial reptiles have dry/tough skin?
to prevent desiccation and to prevent cutaneous respiration
What are tracheae?
small, branched cuticle-lined air ducts
Where are tracheae found?
terrestrial arthropods
Tracheae branch into
tracheoles
What are tracheoles?
series of tubes that transmit gases throughout the body
In arthropods, how is oxygen delivered to cells?
tracheoles are in direct contact with individual cells so that oxygen can diffuse directly across plasma membranes
How does air enter the tracheae of arthropods?
passes through specialized openings of the exoskeleton called spiracles
What are spiracles?
specialized openings of the exoskeleton through which air passes
How are spiracles opened and closed?
valves
What was the major evolutionary mechanism that allowed arthropods to invade land?
prevention of water loss by closing spiracles
Why were gills replaced with lungs in terrestrial animals?
air is less supportive than water; water evaporates
Elaborate on “air is less supportive than water.”
gills lack structural strength and rely on water for support; if a fish were to live out of water, they would have plenty of O2 but would suffocate since the gills would collapse
(T/F) Air is usually saturated with water.
False, air is rarely saturated with water vapor (except after a rainstorm).
Elaborate on “water evaporates.”
Gills would provide an enormous surface area for water loss.
How does the lung minimize water evaporation?
moves air through a branched tubular passage
Describe the directionality of air flow in lungs.
two-way flow in the same airway passage
What natural phenomenon allows for the constancy of atmospheric composition of gases?
convection currents
What is a barometer?
apparatus that measures air pressure
What is the maximum altitude for human survival?
6000 m
Describe the appearance of lungs in amphibians.
saclike outpourings of the gut
Compare the surface area available in the lungs of amphibians to the surface area available in the lungs of other terrestrial vertebrates.
less surface area in amphibian lungs than in other terrestrial vertebrate lungs
The opening to each amphibian lung is controlled by
a valve called the glottis
Which mechanism do amphibians use to breathe?
positive pressure breathing
What is positive pressure breathing (in amphibians)?
they fill oral cavity with air and elevate floor of oval cavity, which pushes air into the lungs
Give an analogy for positive pressure breathing in humans.
forcing air into a person’s lung by performing mouth-to-mouth resuscitation
Which mechanism do most reptiles use to breathe?
negative pressure breathing
What is negative pressure breathing?
they expand rib cages by muscular contraction which creates lower pressure inside lungs, which pushes air into lungs
What are alveoli?
tiny grape-like sacs that provide more surface area for gas exchange
How thick is the epithelium of an alveolus?
one cell thick
How thick are the blood capillaries surrounding alveoli?
one cell thick
What is the distance for gas diffusion in bird/mammalian alveoli?
0.5 to 1.5 micrometers (very small)
Describe the passage of air in the mammalian respiratory system.
air is inhaled through mouth/nose past pharynx into larynx; then passes through glottis; then passes into tracheae; passes into left or right bronchus; passes into bronchioles; passes into alveoli
The mammalian tracheae is divided into
right and left bronchi
In human lungs, how many alveoli are there?
each lung contains about 300 million alveoli
What is the total surface area available for diffusion in the human lung?
80 m^2 (42x surface area of body)
Which animal has the most efficient respiratory system among terrestrial vertebrates?
avians
Where does gas exchange occur in the avian respiratory system?
air is channeled through tiny vessels called parabronchi, where gas exchange occurs
Describe the directionality of air flow in avians.
air flow in parabronchi is one-directional; old air exits lungs by different route
In other terrestrial vertebrates, the two-directional flow of air results in
inhaled fresh air mixing with old, oxygen-depleted air
What two unique structures in birds help with unidirectional air flow?
the anterior and posterior air sacs
How is unidirectional air flow accomplished in birds?
both anterior and posterior sacs expand upon inflation but only posterior sac is filled w/ new air; anterior sac fills with old air pulled from lungs; upon exhalation old air in anterior sac is pushed out of body and new air in posterior sac enters lungs
How many cycles of respiration are there in birds?
two cycles, but the air inhaled in the first cycle isn’t exhaled until the second cycle
Draw out the two cycles of respiration in birds.
draw page 1009, Figure 48.9
In what ways does the unidirectional air flow in birds permit further respiratory efficiency?
crosscurrent blood flow has greater capacity to extract oxygen from air
What is crosscurrent blood flow in birds?
flow of blood through avian lung runs at 90 degree angle to air flow
In terms of everyday life, why do birds need a much more efficient respiratory system?
because they often fly at really high altitudes, where less oxygen is available
How many capillaries can be found in each lung?
about 30 billion (100 capillaries per alveolus)
Blood returning from systemic circulation has a PO2 of
40 mmHg
The PO2 in alveoli is
105 mm Hg
Blood leaving the lungs has a PO2 of
100 mHg
If the PO2 in alveoli is 105 mmHg and blood leaving the lungs has a PO2 of 100 mmHg, what does this mean?
the lungs do a very efficient - but not perfect - job of oxygenating blood
What thin membrane covers the outside of each lung?
visceral pleural membrane
What is the visceral pleural membrane?
thin membrane that covers the outside of each lung
What membrane covers the inner wall of the thoracic cavity?
parietal pleural membrane
What is the parietal pleural membrane?
lines the inner wall of the thoracic cavity
What is the pleural cavity?
the space between the visceral pleural membrane and the parietal pleural membrane; small and filled with fluid
What is the purpose of the fluid in the pleural cavity?
causes the parietal pleural membrane to stick to the visceral pleural membrane, which couples the lungs to the thoracic cavity
Describe why the two lungs aren’t packaged together.
The pleural membranes package each lung separately so that if one lung collapses, the other lung can still function
During mammalian inhalation, how is thoracic volume increased?
through contraction of two sets of muscles: external intercostal muscles and the diaphragm
Contraction of the external intercostal muscles results in
raising of the ribs and expansion of the rib cage
Contraction of the diaphragm results in
the diaphragm lowering and assuming a more flattened shape
What is the diaphragm?
convex sheet of striated muscle separating the thoracic cavity from the abdominal cavity
What kind of breathing mechanism do mammals/humans employ?
negative pressure ventilation
Expansion of the thoracic volume places the thorax and lungs under what tension?
elastic tension
Why do humans have unforced exhalation?
because the relaxation of the external intercostal muscles/diaphragm releases the elastic tension which allows the thorax and lungs to recoil
What muscles are used to force inhalation in humans?
accessory respiratory muscles like the sternocleidomastoid
Each breath in a human moves how much air into and out of the lungs?
tidal volume of 500 mL of air moves into and out of the lungs
What is anatomical dead space?
tubular passages (trachea, bronchi, bronchioles) where no gas exchange occurs
How much tidal volume is contained in the anatomical dead space?
150 mL of tidal volume is in the anatomical dead space
What is the vital capacity?
maximum amount of air that can be expired after a forceful, maximum inhalation
What is the vital capacity in young men?
4.6 L
What is the vital capacity in young women?
3.1 L
Why is the vital capacity clinically important?
abnormally low vital capacity can indicate damage to alveoli
What is hypoventilation?
insufficient breathing to maintain normal blood gas measurements
What is the best indicator of hypoventilation?
rise in blood PCO2
What is hyperventilation?
excessive breathing
What is the best indicator of hyperventilation?
abnormally low blood PCO2
Why is increased breathing during exertion not considered hyperventilation?
because the faster/more forceful breathing is matched to the higher metabolic rate, so blood gas measurements are still normal
Ventilation, generally speaking, is controlled by
the nervous system
Each breath is initiated by
neurons in the respiratory control center
Where is the respiratory control center located?
medulla oblongata
What stimulates the external intercostal muscles/diaphragm to contract?
neurons in the respiratory control center
What causes the external intercostal muscles/diaphragm to relax?
neurons in the respiratory control center stop producing impulses
What kind of muscle is used for breathing muscles?
skeletal BUT they are usually controlled automatically; can be voluntarily overridden
What is the primary initiator for the urge to breathe?
rise in PCO2 rather than a fall in PO2
A rise in PCO2 results in
increased production of H2CO3
What effect does H2CO3 have on blood pH?
H2CO3 lowers blood pH (more acidic)
A fall in blood pH results in
stimulation of chemosensitive neurons in the aortic and carotid bodies
Where are the aortic and carotid bodies located?
aorta and carotid artery, respectively
When stimulated, what do the aortic/carotid bodies do?
send impulses to the respiratory control center, which stimulates increased breathing
What other mechanism, other than aortic and carotid bodies, exists to stimulate breathing when blood pH is too low?
brain contains central chemoreceptors that are stimulated by a drop in the pH of cerebrospinal fluid (CSF)
Why can’t a person voluntarily hyperventilate for too long?
because the decreases in PCO2 and increase in blood pH suppresses the reflex drive to breathe
Why does deliberate hyperventilation allow people to hold their breath longer?
because CO2 levels are lowered, which takes longer to build back up and postpones the need to breathe
For people with normal longs, when does PO2 become a primary initiator?
at high altitudes where PO2 is low
What does COPD stand for?
chronic obstructive pulmonary disease (COPD)
What are COPDs?
any disorder that obstructs air flow on a long-term basis
List the major COPDs.
asthma; chronic bronchitis; emphysema
What happens in asthma?
allergen triggers release of histamine or other inflammatory chemicals which can cause constriction of bronchi or suffocation
What happens in emphysema?
alveolar walls break down and the lung exhibits larger but fewer alveoli; lungs become fibrotic and less elastic; air passages open adequately but collapse and obstruct outflow of air
What is the primary cause of emphysema?
cigarette smoking
Which cancer accounts for more deaths than any other cancer?
lung cancer
Is lung cancer a COPD?
no, it usually follows or accompanies a COPD
What is the most important cause of lung cancer?
cigarette smoking
What is the second-most important cause of lung cancer?
air pollution
Where do most lung tumors originate?
mucous membranes of large bronchi
How do lung tumors affect breathing?
as the tumor invades the bronchial wall and grows around it, it compresses airway and may cause collapse of distal parts of the lung
Why is lung cancer in smokers rarely noticed?
because lung cancer causes coughing but smokers cough anyways, so they don’t really notice
What percentage of patients with lung cancer survive after 5 years of diagnosis?
3%, because lung cancer metastasizes very quickly
Protruding papulae are found in which organisms?
echinoderms
What is the atmospheric PO2?
160 mm Hg
Which is more tolerable, alkalinity or acidity?
alkalinity
Emphysema affects what factor of Fick’s Law?
surface area
(T/F) There are nerve endings in our lungs.
False, we don’t have nerve endings in our lungs
In physiological conditions, how much O2 can blood plasma contain, per liter?
3 mL O2 per liter blood plasma
In physiological conditions, how much O2 can whole blood contain, per liter?
200 mL O2 per liter whole blood
Hemoglobin is composed of
four polypeptide chains
Oxygen-bound hemoglobin is called
oxyhemoglobin
Where does hemoglobin load up with oxygen?
alveolar capillaries of the pulmonary circulation
Oxygen-bound hemoglobin that releases oxygen is called
deoxyhemoglobin
What is the color of deoxyhemoglobin?
darker red, but gives a bluish tinge to tissues
(T/F) Hemoglobin is exclusively used in vertebrates.
False. Used in all vertebrates, but is also used in many invertebrates like annelids, mollusks, echinoderms, flatworms, some protists.
What is the oxygen carrier in non-hemoglobin invertebrates?
hemocyanin
How is hemocyanin different from hemoglobin?
uses copper instead of iron to bind O2; not associated with blood cells but is intend a free protein in the circulating fluid (hemolymph) of arthropods and some mollusks
What percentage of hemoglobin is oxygenated at PO2 = 100 mmHg when leaving the alveoli?
97% of hemoglobin is oxygenated
What percentage of hemoglobin is oxygenated at PO2 = 40 mmHg in blood that returns to the heart through the systemic veins?
75% of hemoglobin is oxygenated
How much of a “reserve” of O2 is there in hemoglobin?
In a person at rest, only about 22% of oxyhemoglobin proteins release oxygen, meaning that 78% of oxygen is left as a reserve
Why is the large reserve of O2 in hemoglobin important?
enables blood to supply needs during exertion AND rest; ensures there’s enough O2 to maintain life for 4-5 min if breathing is interrupted/heart stops pumping
What is the PO2 of venous blood during exercise?
can drop to 20 mm Hg
A second oxygen reserve is found in
myoglobin
Where is myoglobin found?
muscle cells
Myoglobin consists of
a single polypeptide chain w/ iron atom
Which has a higher affinity for O2 - myoglobin or hemoglobin?
myoglobin
How does myoglobin function as a backup?
when hemoglobin levels are exhausted, myoglobin kicks in with extra O2
How can animals like the elephant seal stay underwater for long periods of time (in terms of hemoglobin/myoglobin)?
because they have high levels of O2 stored in myoglobin in their muscle cells
CO2 + H2O yields
H2CO3
H2CO3 dissociates into
HCO3- and H+
Where does H2CO3 dissociation occur?
inside RBCs
What effect does a lower pH have on hemoglobin’s affinity for oxygen?
promotes release of O2; shifts Bohr curve to the right
What effect does a higher temperature have on hemoglobin’s affinity for oxygen?
promotes release of O2; shifts curve to the right
What percentage of CO2 is simply dissolved in plasma?
8% of blood CO2 is simply dissolved in plasma
What percentage of blood CO2 is bound to hemoglobin?
20% of blood CO2 is bound to hemoglobin
Where does CO2 bind to in hemoglobin?
on the protein part (not to the iron parts), so it doesn’t compete with O2
What effect does CO2 binding to hemoglobin have on binding to O2?
CO2 binding causes hemoglobin’s shape to change which lowers affinity for O2
Where is CO2 not dissolved in plasma or bound to hemoglobin found?
diffuses into RBCs where it combines with H2O to produce H2CO3
Which enzyme catalyzes the combining of CO2 and H2O?
carbonic anhydrase
What happens to the H+ that results from the dissociation of H2CO3?
H+ binds to deoxyhemoglobin
What happens to the HCO3- that results from the dissociation of H2CO3?
moves out of RBC into plasma via a transporter that exchanges one Cl- for one HCO3-
What is the chloride shift?
when an HCO3- inside an RBC is replaced with a Cl- via a transporter
CO2 is primarily transported in what form?
as HCO3-
Why is the diffusion of CO2 into the RBCs important?
it creates a diffusion gradient that allows more CO2 to move into the plasma from surrounding tissues
What is the major buffer of blood plasma?
HCO3-
What happens to H2CO3 in the lungs?
the lower PCO2 causes carbonic anhydrase reaction to proceed in the reverse reaction, which creates H2O and CO2, and CO2 diffuses out and is released in the next exhalation
Which two other gases can be transported by hemoglobin?
NO and CO
NO is important for
vessel dilation
Why is CO poisonous?
because it binds more strongly to hemoglobin than does O2
Victims of CO poisoning often have what color skin?
bright red skin
What happens to HCO3- replaced with Cl- once the blood reaches the alveolar capillaries?
diffuses into cell, reacts with H+ to form H2CO3, then decomposes into CO2 + H2O, diffuses into alveolus, exhaled
