Exam 1-- 4410 Flashcards
Why are mammals unable to breathe water in terms of the physical properties of water
Higher solubility of CO2 compared to O2 in water.
Mammals have lower ventilation rates due to the abundance of oxygen in air.
Thus, they are unfit to breathe in CO2 rich water without experiencing acidosis
Why are mammals unable to breathe water in terms of the physical properties of air
Oxygen content is 30 times higher in air than water. A mammal’s anatomy is unable to take in 30 times as much water in order to satisfy their oxygen demands.
Why are mammals unable to breathe water in terms of ventilatory mechanics
Tidal airflow through the respiratory system of mammals would require the water to move both in and out the same route to lungs.
The water cannot pass through quickly enough, with adequate oxygen uptake, leading to drowning.
Why are mammals unable to breathe water in terms of respiratory anatomy
As mammals evolved to survive on land, they developed more efficient ways to eliminate CO2 through pulmonary systems. Thus, mammals do not have gills as respiratory organs, which is the principle method of breathing water. The lungs of mammals do not have enough surface area to absorb appropriate amounts of oxygen from water.
Why can’t a trout breathe air in terms of the physical properties water
There is a low solubility of O2 in water. Therefore, trouts have high water ventilation rates fit to extract O2 from water. So, they are unfit to respirate in an environment with an abundance of O2.
Why can’t a trout breathe air in terms of the physical properties air
Solubility of O2 is greater in the air than in water. Water breathers always have less CO2 in their body fluids than air breathers. And, they are equipped to extract dissolved O2 from water, not the air where O2 concentrations are much higher
Why can’t a trout breathe air in terms of ventilatory mechanics
Ventilation in trouts occurs at a high rate, where water flow (convection) across the gills is countercurrent and unidirectional. Here, water comes into contact with less oxygenated blood and creates a diffusion gradient. As a result, countercurrent gas exchange results in the most complete extraction of oxygen from the water
Gills are ventilated by a buccal and opercular pump: open mouth creates (-)pressure -> water flows from buccal to opercular -> opercular opens, pulling water in -> mouth closes and buccal pump pushes water across gills
Why can’t a trout breathe air in terms of respiratory anatomy
Trouts have internal gills that are used as respiratory structures. As a result, they need a lot of water to pass over the gills so the lamellae can pick up oxygen through a direct diffusion gradient. The oxygen tension of the blood is less than that of water, thus maximizing oxygen uptake in the water
Gill structures collapse when taken out of water. When collapsed, the gills are not longer exposed to oxygen.
Why do larval fish not require gills for gas exchange, but adults do
Larval fish only need diffusion to obtain adequate oxygen from their environment. Their thinness and smallness allows for greater diffusion cutaneously.
Adult animals grow larger and thicker, so, they must rely on both convection and diffusion to obtain adequate oxygen uptake from the environment.
Tuna vs Sole: gill morphology
tuna have more lamellae that are thinner and more densely packed than the sole
Tuna vs Sole: critical swimming speed
tuna have much higher swimming speeds than sole
Tuna vs Sole: myocardial properties
Tuna has 60-70% compact myocardium, while sole has 100% spongy myocardium
Tuna vs Sole: ventilatory mode
tuna ram ventilate due to their high swimming speed, making it more efficient to extract O2 through the mouth to gills via the force of motion through water. Rather than an active buccal pumping which decreases swimming speed
Tuna vs Sole: coronary blood supply
tuna has more coronary blood supply because it is dependent on the amount of compact myocardium. However, soles have none
which fish is high performance, and which is sluggish (tuna vs sole)
high– tuna
slug– sole
Hypoxia
deficiency in the amount of oxygen reaching the tissues and lower oxygen partial pressures
Normoxia
normal O2 levels in the tissue and normal O2 partial pressures in the environment
Hyperoxia
high partial pressure of oxygen in the environment
What about the physical and biological environments requires pupfish to be so hypoxia-tolerant
as salinity and temperature increase, gas solubility decreases, according to Henry’s law
What is the primary respiratory organ of pupfish. What is its anatomical arrangement relative to the water and how does that allow a more efficient extraction of O2 from the water than other gas-exchange organs (lung)
primary organ– gills
arrangement– water and blood flow through the lamella in opposite directions, enabling countercurrent exchange, which enhances the efficiency of oxygen extraction from water. This arrangement maintains a concentration gradient along the entire length of the gill, ensuring that oxygen continually diffuses into the bloodstream, even when the oxygen concentration in the water becomes low. This is especially efficient in pupfish, as they live in extreme environments more prone to hypoxia, where they must be able to optimize O2 uptake
Under normal conditions, how does the arterial Pco2 of the pupfish compare to a dog? What, specifically, accounts for this difference?
PCO2 pupfish has lower arterial PCO2 than a dog because it ventilates more due to low concentration of oxygen in water.
Solution A: O– 100; PO2– 50
Solution B: O– 50; PO2– 100
which will have higher osmolarity
Solution A
osmolarity is directly proportional to solute concentration, Solution A with an oxygen concentration of 100 mol/L is likely to have a higher osmolarity compared to Solution B with an oxygen concentration of 50 mol/L
Solution A: O– 100; PO2– 50
Solution B: O– 50; PO2– 100
which will have a higher temperature
Solution B
Oxygen saturation is the lowest in warmer water, because by Henry’s Law, gas solubility decreases as temperature increases
Solution A: O– 100; PO2– 50
Solution B: O– 50; PO2– 100
which is most like blood
Solution B
Blood’s Po2 range is within 75-100 mHg, which aligns with Solution B’s Po2
Solution A: O– 100; PO2– 50
Solution B: O– 50; PO2– 100
which has the higher O2 solubility
Solution A
solubility = [Gas] / Pgas
= 100/50 = 2
2 is higher than 1/2 in Sol B
Solution A: O– 100; PO2– 50
Solution B: O– 50; PO2– 100
If solutions A and B were separated by a gas permeable membrane (like gill epithelium), what direction will oxygen diffuse?
B - > A
There is a pressure gradient created, as B has a higher Po2 than A
Describe the basic model of how a fish ventilates its gills. (summer and ferry)
Action of 2 pumps: a pressure pump that pushes water across the gills from the oropharyngeal to the parabranchial cavity, and a suction pump that draws water across the gills from the oropharyngeal into the parabranchial. Together, they keep water flowing continuously
the flow is continuous and counter-current
methods (summer and fairy)
measured KINEMATICS with SONOMICROMETRY and found displacement in mouth and gills
measured PRESSURE simultaneously from the oropharyngeal and parabrancial chamber with TRANSDUCER BRIDGE AMPLIFIERS
measured FLOW through IMAGES taken through ENDOSCOPY methods
What finding challenged the accepted model of gill ventilation in fishes? What are the implications for gas exchange? (summer and ferry)
Pressure and suction pumps do not always work perfectly in some fish, creating a pressure differential where for some portion of the respiratory cycle, the water flow is co-current with the blood flow, rather than counter-current, as it should be. This would require changes of the models of gas exchange
The greatest efficiency for gas exchange is not always required. The skate, for example, only needs the bare minimum to survive and they can choose one mode over the other based on their situation. Like it may not need a lot of O2 from water, esp if theyre sluggish
What, specifically, did Moalli and Burggren challenge about the existing model of gas exchange in frogs?
The fact that traditional models have treated skin as a single blood compartment, such as a single capillary model. This model reveals perfusion limitations in CO2 elimination
they proposed a multi-capillary model, which involves changes in capillary recruitment, thus changes in the surface area acrosswhich CO2 elimination from the blood can occur. Here, perfused capillaries cause major changes in CO2 elimination
What happened to oxygen consumption and carbon dioxide production when the frogs were moved from water to air, and then back to water? What physiological mechanisms accounted for these changes?
water to air
- blood flow decreased
- number of perfused capillaries decreased
- gas exchange ration falls below 1
back to water
- cutaneous blood flow and capillary recruitment increased
- gas exchange ratio increases to above 2
Why do you think the frog relies on its skin to excrete carbon dioxide?
Because water and air are such different mediums, maintaining a functioning respiratory system across this transition is crucial for survival. Cutaneous respiration helps bridge this gap by allowing for gas exchange that doesn’t depend on aquatic gills or terrestrial lungs.
frog has a lung that is not totally different than that of lungfish. buccal pump is able to help ventilate, but its not too great to satisfy them to eliminate CO2. So, the frog relies on skin to get rid of what their lung cannot remove through the breath
How do the mechanics of lung ventilation differ in frogs compared to other tetrapods? (Brainerd and Owerkowicz and Owerkowicz.)
Frogs ventilation differs in costal ventilation, most tetrapods use axial muscles, frogs use a buccal pump mechanism. air is drawn into the mouth and then pumped under positive pressure into the lungs. different then birds for example as they use intercostal muscles to ventilate
What is costal breathing and which amniotes use it
costal breathing- expansion and contraction of the lung cavity through movement of the ribs
lizards, birds, and mammals
What amniotes don’t use costal breathing
Crocodylians and turtles
How do crocodylians ventilate
piston pumping: diaphragmaticus musc;e retracts liver, expanding the thoracic cavity, which resembles a piston sliding in a cyliner
How do mammals ventilate
diaphragm muscle: contracting this expands the thoracic cavity, creating negative pressure which draws air into lungs.
Costal muscles are present, but not the primary from of ventilation
How do turtles ventilate
diaphragmaticus and internal oblique:
- oblique increases the volume of the abdominal cavity causing lung inflation.
- diaphragmaticus aids in expiration
Why has the loss of lungs in plethodontid salamanders been a successful evolutionary strategy?
eliminating the lung has allowed them to do some things that other animals cannot.
lungless means they do not have an anatomic constraint for respiratory movement, so their tongue can be long, so its feeding is more precise when hunting. without the buccul pump, the brain can become more specialized. better than other salamanders to eat from a distance
What is the arrangement of air flow relative to blood flow called in the bird lung?
the arrangement of airflow relative to blood is cross current exchange
How does the Po2 of the arterial blood compare to the Po2 of the expired air?
in the avian lung the PO2 in arterial blood is higher than the PO2 of expelled air
How does this compare to reptilian and mammalian lungs? (Bretz and Schmidt)
in reptilian and mammalian lungs, the PO2 of the arterial blood is not as high as the PO2 of expired air
what are two other differences between bird and non-croc reptile lungs
birds have air sacs in their respiratory system, which provide continuous flow of air through the lungs. Avian lungs also have unidirectional air flow, which enhances the efficiency of gas exchange
What is the purpose of the study of Bretz and Schmidt-Nielsen?
investigate the respiratory system of ducks to understand the patterns of airflow during different phases of the ventilation cycle
most important part of ducks by bretz
the avian respiratory system functions as a two-cycle pump
Describe how air flows in the avian respiratory system during a single ventilatory cycle
- during the 1st cycle of inspiration, fresh air goes to the posterior air sac, and expands
- during the 1st cycle of expiration, the posterior air sacs shrink and inspired gas moves from the posterior air sacs, pushing through the lung
- during the 2nd cycle of inspiration, after passing through the lung, has fills the anterior air sac, which expands
- during the 2nd cycle of expiration, the anterior sacs shrink and gas from the anterior sacs flows to the main bronchus, trachea, and out of the body
this is a continuous, unidirectional process where cycle 1 and 2 inspiration occur simultaneously
what conventional wisdom are farmer and sanders challenging
that alligators are tidal, coastal breathers like humans. that they change the shape of their chest wall and volume of lungs
what hypothesis are farmer and sanders testing
airflow in alligator lungs is unidirectional
what is the evolutionary significance of farmer and sanders
unidirectional air flow did not randomly appear as people used to believe. There was a progression as systems built on top of systems.
Developed crosscurrent exchange on top of unidirectional flow, which was basically starting material for the bird lung
why are the findings of farmer and sander considered controversial
unidirectional flow lung that still changes volume is significantly controversial as it is more believable to have one that does not change value if it is in unidirectional flow
What factors determine vascular resistance in the cardiovascular system ? Which is most important ?
radius, viscosity of the medium, and length of the vasculature
radius of the vasculature is the most important
What factors determine whether or not blood flows from one region of the cardiovascular system to another?
blood pressure, blood volume, resistance
Pressure gradient: blood flows from high to low pressure
Resistance: change in vessel diameter can affect this
Blood viscosity:
How does blood pressure change as it travels through the cardiovascular system? What specifically accounts for these changes?
Pressure: BP falls as it travels through the circulation from arteries to veins. The system loses pressure as it travels down vessels with varying diameters
How does velocity change as it travels through the cardiovascular system? What specifically accounts for these changes?
Blood velocity decreases as it enters the capillaries, and begins to increase as it leaves the capillaries. This is due to the drastic increase in total cross sectional area of the vasculature within capillaries.
How do systemic blood pressures in non-crocodilian reptiles compare to those in mammals and birds?
Reptiles: pulmonary BP = systemic BP
Mammals / Birds: pulmonary BP < systemic BP
Systolic/Diastolic BPs of reptiles are much lower compared to mammals/birds
reptiles only have 1 ventricle, meaning they lack an interventricular septum. Thus, systemic circulation is regulated by constraints of pulmonary circulation.
What directly determines the amount of R-L cardiac shunting in reptiles
- the ratio of resistance of pulmonary circulation vasculature / resistance of systemic circulation vasculature (diameter). Therefore, the ANS determines resistance and the PNS tone via the vagus nerve
- systemic dilation can make R-L shunt, or an increase in pulmonary vascular resistance (happens in apnea when the animal is not breathing)
How does cardiac shunting in turtles, lizards, and snakes differ from cardiac shunting in alligators?
Turtles, lizards, and snakes:
- 1 ventricle and 2 atria.
- lack an intraventricular septum
- intracardiac shunting– they can shunt in both directions
Alligators:
- 2 ventricles and 2 atria
- Have an interventricular septum
- extracardiac– only get right to left shunting
Under what circumstances is a R-L shunt observed in reptiles?
Parasympathetic response to ANS:
- decrease in arterial o2 saturation
- degree is dependent on parasympathetic tone being activated
- activation of the vagus nerve
- pulmonary resistance to increase, leading
to fall in O2 saturation
Under what circumstances is a L-R shunt observed in reptiles?
Sympathetic response of the ANS
increase in sympathetic tone, favors an increase in arterial O2 saturation
- systemic muscles are only innervated by
sympathetic
- sympathetic activation increases
systemic resistance, without
changing pulmonary resistance
What are the different layers of tissue in the heart? What accounts for their quantitative variation across different species? What are the trade-offs associated with having more of one than another?
Different Layers:
- Compact myocardium (supplied by coronary circulation)
- Spongy
Variation: the higher the VO2max of a fish, the more compact myocardium, as that is what enables there to be coronary circulation. The more compact to spongy ration, the more active the fish
Trade-offs: Depends on the lifestyle of the fish. Active fish require more compact myocardium for coronary circulation to supply myocardial oxygen for their high cardiac performance. Sluggish fish usually only have spongy myocardium because they are sedentary.
Experimental approach of frog capillary people (Moali)
- Measurement of BLOOD PERFUSION with MICROSPHERES.
- CAPILLARY RECRUITMENT under various environmental conditions
- ANOVA statistical analyses
How did Moali frog capillary people change what was understood about cutaneous gas exchange at the time
- changes in capillary recruitment can significantly affect cutaneous gas exchange. So, assuming the skin of amphibians or any other animal to be a single, diffusion-limited compartment under all conditions is inappropriate.
- CO2 elimination is more reliant on cutaneous gas exchange than exhaling via mouth.
What are three important differences between the cardiovascular system of fishes and that of tetrapods?
- 1 chambered heart
- Max cardiac output constrained by pressure lungs/gills/ABO can sustain
- Only deoxygenated blood passes through heart
describe the cardiac anatomy of a fish, and the route a single erythrocyte takes
1 chambered heart
Max cardiac output constrained by pressure lungs/gills/ABO can sustain
Only deoxygenated blood passes through heart
oxygenated blood travels from the gills to the systemic tissues, which send deoxygenated blood to the heart and then the gills, which makes the blood oxygenated, and the circular path continues.
What hypothesis do Farrell and Steffensen (myocardium) test
is coronary circulation essential for maximum aerobic performance?
how do farell and steffenson (myocardium)– methods, and what was the outcome
- surgically placed a silk threat around the coronary artery w/o tightening it, and the fish recovered overnight
- measured critical swimming speed (Ucrit)
Ucrit = Ui + [(ti / tii)(Uii)] - tightered the loop on the arteries to ligate them
- measure Ucrit again
- killed the fish to verify ligation; measured the proportion of compact to spongy myocardium
outcome: Ucrit was reduced by 35.5% by ligation (swimming performance was reduced)
Describe the conventional hypothesis concerning lung evolution in fishes?
fish evolved to add oxygen to the circulation in aquatic environments where oxygen levels are low
What is her (farmer) hypothesis concerning lung evolution in fishes?
the lung evolved to supply oxygen to the heart of bony fishes in order to support high levels of activity
by extension, cutaneous respiration of extant amphibians and the intracardiac shunt function to oxygenate the right side of the heart
oxygenated blood returning from the lung could supplement the oxygen supply during exercise
What problems did Farmer identify in this hypothesis?
Problem 1: paleontological evidence suggest that lungs evolved in marine fish where the water is well-oxygenated
Problem 2: most extant fish with lung or air-breathing organs are found in water that is well-oxygenated or they still rely most on the gill for oxygen uptake (if you have gills, why live in an oxygenated environment)
Problem 3: If the lung is supposed to service the brain, why is it going to the heart?
predictions based on farmer’s hypothesis
- Fossilized lunged fishes should be found uniformly distributed in oxygen-rich and oxygen-poor environments and should show characters consistent with an active lifestyle
- Lung use will be related to activity and relatively insensitive to aquatic oxygen
- Causes other than marine versus freshwater habitat determine the presence or absence of lungs in fish - benthic lifestyle, aerial predation, coronary circulation
What does farmer believe the implications are for the evolution of the tetrapod heart?
- Amphibians - may rely on cutaneous circulation to supply oxygen to the heart
- Turtles, lizards, snakes - may rely on intracardiac shunting to supply oxygen to the heart
- Lineages which lost the ability to shunt should have evolves extensive coronary circulations
Benefits of R-L shunt
Increased Body Temperature:
- redistribute blood away from the lungs, thus reducing heat loss across the pulmonary vascular bed, and “optimize” the warming of the body
peripheral vasodilation
Digestion and Growth
- rich blood to parietal cells which promote gastric acid secretion
In exercise
- more efficient gas exchange
