final exam Flashcards
Why can’t a trout breathe air? Please answer this question in terms of the physical properties water and air
There is more concentration of oxygen in air and less in H2O
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.
Define hypoxia, normoxia, and hyperoxia.
Hypoxia- deficiency in the amount of oxygen reaching the tissues, lower oxygen partial pressures
Normoxia- normal oxygen levels in the tissue, normal oxygen partial pressure in environment
Hyperoxia- high partial pressure of oxygen in 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
Solution A: O– 100; PO2– 50
Solution B: O– 50; PO2– 100
which will have higher osmolarity
If all else is equal, there is a negligible effect on osmolarity, as gases dissolved at biological levels have a negligible effect on osmolaritylikely 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
- 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– fish gill ventillation)
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
purpose (summer and fairy)
what about the status quo ?
evidence that the pressure and suction pumps do not always work in perfect phase in elasmobranch fishes, leading to periods of higher pressure in the parabranchial than in the oropharyngeal cavity.
We investigated the existence and consequence of such pressure reversals”
What finding challenged the accepted model of gill ventilation in fishes?
What are the implications for gas exchange?
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 is costal breathing, who uses it, and for those who don’t, what do they do ?
costal breathing: expansion and contraction of the lung cavity through movement of the ribs
use it: birds, mammals, lizards
crocs and turtles
what do crocs and turtles do instead of costal breathing
crocs–use piston pumping, diaphragmaticus muscle retracts liver, expanding thoracic cavity, resembling a piston sliding in a cylinder.
turtles– use internal oblique. oblique increases the volume of the abdominal cavity causing lung inflation.
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?
How does this compare to reptilian and mammalian lungs? (Bretz and Schmidt)
in the avian lung the PO2 in arterial blood is higher than the PO2 of expelled air
in reptilian and mammalian lungs, the PO2 of the arterial blood is not as high as the PO2 of expired air; “sort of. At best, its equal”
what are two other differences between bird and non-croc reptile lungs
- Birds have air sacs in their respiratory system, these air sacs provide continuous flow of air through the lungs.
-Avians 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 the ducks.
understand the patterns of airflow through the respiratory system during different phases of the ventilation cycle
Describe the design of their experiment (Bretz and Schmidt)
- ducks rested in natural upright position
- tube was inserted into various airsacks and air sac pressure was recorded
-ducks inhaled marker gas (argon), the partial pressures of argon was measured. - Argon partial pressures and air sack pressures were compared against each other
What was the most important finding of the study by Bretz and Schmidt-Nielsen?
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
alligators are tidal, coastal breathers like humans. They change the shape of their chest wall and volume of lungs.
What hypothesis are F and S testing in their study?
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
What did their experiments show? Do they make sense? Why?
Showed that airflow always go to same direction no matter what phase
For inspiration, unidirectional air flow toward head, and for expiration, unidirectional air flow toward tail
It makes sense - crocodiles are an ancestor of aves, so there must be some evolutionary similarity between the two. It does make sense, but there are a lot of unexplained parts.
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 whether or not blood flows from one region of the cardiovascular system to another?
- Pressure gradient: blood flows from high to low pressure
- Resistance: change in vessel diameter can affect this
According to Hicks and Wang, what are three possible benefits from having the ability to right to left shunt? Please explain how each works.
- Increased Body Temperaturez; “to maximize heating rates, the R-L shunt would 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
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
Describe the cardiac anatomy of a fish and the route that a single erythrocyte takes as it travels through its circulatory system.
Max cardiac output constrained by pressure lungs/gills/ABO can sustain
Only deoxygenated blood passes through heart
default fish cardiovascular pathway:
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 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.
What hypothesis do Farrell and Steffensen test and how do they test it?
What was the outcome of their experiment?
hypothesis: is coronary circulation essential for maximum aerobic performance?
how do they test it
- 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 and 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)
What was the purpose of the Taylor locomotion and cost of transport study
to elaborate the relationship between energetic cost of running and the body weight of mammals
Taylor et al’s experimental approach to quantifying the cost of running in mammals
- several rats, squirrels, and mongrel dogs were trained to run on a treadmill
- O2 consumption rate was measured while the animals ran at increasing speeds
- waited for the animal to reach a steady-state
- the rodent treadmill was enclosed in a plastic chamber and dogs wore a mask
How did the cost of running change with running speed in Taylor et al’s study
The cost of running 1 km reaches a minimum value– minimum cost of running.
As running speed increases, the cost of running will decrease but then reach the minimum value.
Cost of running will remain constant after it reaches the min cost of running.
How did the cost of running change with body size
As animal size decreases, the cost of running increases.
What did Taylor et al find when they extrapolated metabolic rate back to zero velocity?
What accounted for this?
Resting on the treadmill VO2 was extrapolated back to 0 and found to be higher than measured resting VO2
This is because the respiratory, cardiovascular, central nervous system and more were ramping up to get ready to run (upregulation)
According to Kram and Taylor, what two factors should directly determine the metabolic cost of running?
- Cost of supporting the animal’s weight
- Time course of force generation
Why did Kram and Taylor subtract the Vo2 extrapolated back to zero speed?
To determine how much oxygen is consumed (energy required) for just the skeletal muscles during running
How does stride length relate to body mass in animals in Kram and Taylor’s study?
Stride length increases with body mass in animals. Lower stride frequencies for larger animals.
According to Kram and Taylor’s study, why is running more expensive for smaller animals?
Animals with shorter legs have shorter stride lengths and higher stride frequencies. Therefore, higher transport costs
What is the fundamental problem that must be overcome for a muscle to achieve high contraction frequencies?
How does one get extremely high contraction frequencies without temporal summation and tetanus?
What three factors determine the frequency with which a skeletal muscle can contract and relax?
- Fast cross-bridge detachment rates
- Have a less Ca2+-sensitive troponin isoform
- Duration of the Ca2+ transient is shorter
Why is the toadfish sonic muscle able to achieve higher contraction frequencies than rattlesnake tail-shaker muscle?
- Has a special myosin isoform that has a more rapid detachment rate
- vibration of swim bladder at 200 Hz
What are two trade-offs for having the specialized muscles that toadfish and rattlesnakes have with respect to muscle function?
tradeoffs between muscle % SR, mitochondria, and myofibrils
- more myofibril: more mass cause more cross bridges (force)
- more SR: more space for Ca, which upon release can activate more cross bridges and can help rapidly uptake it as well, which is important for speed
- high frequency contractions are expensive, requiring a lot of ATP (increased mitochondrial volume).
- Does not generate much force (reduced myofibril volume)
When Wilz and Heldmaier extrapolated the dormancy metabolic rate to 36°C assuming a Q10 of 2.5, they found that it was lower than the values they measured. What does this say about the metabolic rate of a dormant edible dormouse?
There is a temperature independent mechanism for metabolic depression
What are two mechanisms used by hummingbirds to achieve simultaneous high contraction frequencies, force production, and fatigue resistance in their flight muscles?
To beat zero-sum game (get high frequency, force, and fatigue resistance in muscle)
- increase operating temperature of a muscle (enables them to achieve high rates of muscle contraction + force)
- increase the packing of the mitochondrial cristae (get the most out of ATP)
What are the differences between hibernation, aestivation, and daily torpor?
Hibernation: temperature-independent reduction in metabolic rate that occurs during the winter
Aestivation: temperature-independent reduction in metabolic rate that occurs during summer
Daily torpor: daily decrease in metabolic rate that is temperature-independent
Why is torpor and hibernation considered to a strategy that conserves energy?
Why do small animals benefit more?
- Especially in colder temperatures, thermogenesis to defend body temperature is energetically expensive.
- So, Torpor and hibernation allow Controlled lowering of the metabolic rate (MR) during resting conserves energy by not having to defend body temperature against the environment.
- large amount of energy saving due the the process of being downregulated as a result of torpor
- allows them to thrive in harsh condition
- Stop metabolism and reset the set points in the hypothalamus to a lower temp. Change metabolic flux rates to produce less metabolic heat.
- small animals benefit more because of a high mass-specific metabolic rate, which large animals do not have
- Hibernation and torpor allows for the metabolic rate of small animals like bats and ground squirrels to be independent of body weight
What did Wilz and Heldmaier conclude about the three dormancy states?
What accounted for any differences seen?
Conclusions:
1. cooling and conductance rates were identical
2. time aroused was dependent on ambient temperature (indirect)
3. No difference in the metabolic rate of hibernation, estivation, or daily torpor after the first 8 hours of dormancy
4. Metabolic rate in daily torpor is higher than metabolic rate in hibernation and estivation
- daily (shortest): throughout the year and 3-21 hr bouts
- hibernation (longest): 36-768 hours (32 days)
- estivation: 69-106 hrs (4.4 days)
Accounts:
1. Cooling rate is independent of dormancy state.
2. Metabolic rate decreases more quickly than body temperature
3. Conductance is independent of ambient temperature
What was the purpose of the study by Wilz and Heldmaier?
Question: What are the physiological differences between hibernation, aestivation, and torpor?
Answered this by comparing metabolic depression, hypothermia, and arousal in all 3 forms of dormancy
What conventional view of hibernation were Toien et al challenging in their study of bear hibernation?
Conventional view: Only small hibernators show a temperature-independent decrease in metabolic rate with hibernation (true hibernation)
The question: What is the relationship between body temperature and metabolic rate in bears?
What was the most important finding of the study?
- metabolic rates rise independently of core temperatures, indicating that metabolic rate is suppressed during hibernation periods
- When body temperature fell from 37C to 32C, metabolic rate fell by 70% (a lot more than the expected 35% drop)
- Heart rate fell from 55 to 9 bpm, indicating their metabolic rate is depressed
- Evidence of cardiorespiratory synchrony (rhythm between cardiac and respiratory function)
State four commonalities between bears and rodents in regard to hibernation.
- Decreased metabolic rate
- Reduced heart rate
- no diurnal body temperature cycle
- do not eat or drink for 6 months
What are two important differences between hibernation in bears versus rodents?
In bears…
1. body temperature falls much less
2. no interbout arousals
What are the two primary strategies for surviving subzero temperature called?
How do they differ from one another? Give one example of each strategy.
Freeze tolerance: allows body water to freeze- mechanisms to prevent or limit the damage caused by formation of ice crystals
- ex: painted turtles avoiding dehydration
Freeze avoidance: mechanisms that prevent ice crystal formation
- ex: ground squirrels supercooling
What is a freezing point exotherm,
when does it occur, and
why is it important in determining how hatchling turtles and wood frogs survive subzero temperatures?
Freezing point exotherm: when water changes from a liquid to a solid
Occurs when there is a release of heat that is detected as an increase in temperature
Important in turtles and wood frogs:
Determines when an animal freezes
What is the primary cause of cellular death when an animal freezes?
How do hatchling turtles and wood frogs prevent this from happening?
Primary cause: Cellular dehydration when freezing
due to the formation of crystals in/out of the cell causing shrinkage beyond the minimal cell volume =irreversible damage.
Turtle: use cryoprotectant accumulation of solutes (glucose, glycerol, and taurine) in cells to prevent dehydration during ice formation and keep H2O there
What makes a turtle’s pond anoxic during the winter?
Biomass competition combined with lack of gas exchange in atmosphere
- Lack of diffused oxygen due to icing over of ponds (no gas exchange with atmosphere)
- Lots of respiring biomass in the pond (animals and plants)
What are the primary metabolic end-products produced by turtle tissues under normoxic conditions?
What is its primary metabolic end-product during anoxic hibernation?
What fuel is used to support metabolism during anoxic hibernation?
What organ supplies this fuel?
Normoxic: Lactic acid and atp
Anoxic: Co2 atp water
Fuel: glycogen
Organ: liver
What are the three primary adaptations that allow turtles to survive anoxia?
1) Metabolic depression
2) Extremely large glycogen stores
3) Extremely large buffering capacity
What are three ways that a turtle depresses its metabolism?
- Reductions in cardiovascular activity..
- The animal becomes dormant.
- Downregulation of glycolytic enzymes.
- Decreases in protein synthesis
- Arrest ion channels and translation
- Decreases in Na, K and Ca conductance
- Reduces ATP expenditure on ion pumping.
What turtle tissue is most responsible for buffering lactic acid during long periods of anoxic hibernation?
Describe the two mechanisms by which this occurs?
What two minerals within this tissue are most important?
- Skeletal Tissue (shell)
Mechanisms
1. Buffers (carbonates) are released into the extracellular fluid (ECF) to enhance buffering capacity during anoxia
2. Lactate is sequestered in shell and bone during anoxia and released during recovery
Minerals: Calcium carbonate and magnesium carbonate
What do goldfish and crucian carp produce as primary metabolic end-product during anoxia?
What is the primary advantage of using this biochemical strategy?
What is the primary disadvantage?
Produce ethanol
Advantage: Avoiding lactic acid accumulation prevents depletion of buffers and maintains pH near normal values
Disadvantage: Carbohydrate lost to the water cannot be recovered, meaning a significant energy loss
What is the main metabolic fuel supporting energy production during anoxia in goldfish and crucian carp?
Glycogen
Describe how hypoxia leads to neuronal death in hypoxia-sensitive neurons. (Bickler, Buck, Nilsson)
Glutamatergic Excitotoxicity
- Excitatory cascade leads to greater loss of ATP in cells
> Net accumulation of sodium in cell larger in cell
than out of cell
> Water follows sodium into cell; cell swells and
bursts (necrosis)
- Cell death because cells accumulate huge amounts of calcium
Depolarization stimulates excessive release of Glutamate, overwhelming the neuron’s capacity to regulate its levels, triggering excitotoxicity
How do the ion channels in turtle neurons respond to hypoxia?
What is this physiological response called?
Potassium leaks out of normoxic brain tissue faster than anoxic one
Ion Channel Arrest -> physiological response where channels become inactivated
overall, when you take out oxygen turtle neurons become less leaky due to Potassium channels closing
What neurotransmitter activates NMDA receptor channels?
What ion does it conduct?
What happens to this ion channel in turtle neurons during anoxia?
Neurotransmitter: Glutamate
Ion: Ca2+
Ion channel in anoxic turtle neurons:
- Doesn’t accumulate calcium at all during anoxia
- Able to avoid Ca2+ accumulation by reducing the conductance of NMDA receptor
- Overall, In anoxia: receptors have reduced sensitivity to NMDA and Glutamate to prevent Ca2+ from entering the cell
What are two mechanisms by which NMDA receptor channels are down-regulated in hypoxia-tolerant neurons?
- Reduce conductance of NMDA receptors (ion channel arrest)
- Phosphorylate the channels (Post-translational modifications). Change the composition of the receptor
ATP consumption rates are lower, preventing excitotoxicity
What other intracellular signaling molecule is likely involved in coordinating the responses of turtle neurons to hypoxia?
Calcium
How do the behavioral responses to anoxia compare between crucian carp and turtles?
Crucian Carp:
- Relative active
- Produce ethanol
- Less profound metabolic depression
- Only factor limiting survival is the size of glycogen store
Turtle
- Remain relatively inactive
- Produce lactic acid
- Greater metabolic depression
What happens to cerebral blood flow during anoxia in crucian carp and what function does this change serve?
Cerebral blood flow increases
support its higher activity
- ensure lactic acid is being flushed out
- deliver glucose to the brain to produce ATP, keeping the brain functioning
What happens to brain GABA levels during anoxia in crucian carp and what function does this change serve?
they are elevated to calm neural activity, thus avoiding excitotoxicity
What important anoxia tolerance strategy is used less by the crucian carp brain but is used in the turtle brain?
Crucian carp do not show ion channel arrest
What are the two basic problems an animal faces when it dives to extreme depths?
- O2 availability
- The Bends (decompression sickness)
What causes The Bends and how do diving mammals avoid it?
Decompression sickness due to formation of bubbles in the tissues and bloodstream during rapid ascent
Avoid it: diving mammals will collapse their lungs
Here, Alveoli collapse but airways do not
What are two adaptations of diving mammals’ oxygen transport system that allows it to have extended aerobic dive times?
- Large O2 stores in myoglobin
- Greatest percentage of total oxygen store is in blood
What circulatory changes occur during diving and what functions do they serve for the animal? How do they relate to dive duration?
Diving bradycardia (decrease heart rate) → heart rate decreases during longer dive duration
Peripheral vasoconstriction (reduce blood flow to all but essential organs) → Muscle O2 decreases as dive length increases
Dive Duration:
- Diving bradycardia depends on dive duration
- The longest dives have the lowest heart rate
What is the oxygen debt and how does it relate to lactate production and oxygen consumption?
- Muscles may switch to a different way of making energy that doesn’t need oxygen right then, but it leaves behind a “debt” of oxygen that still needs to be paid back later.
- Oxygen required to clear lactate and is proportional to ATP needed to clear lactate
What is the major difference between diving turtles and marine mammals in how they adapt to extended apneic periods?
Turtle Dives
- anaerobic
- accumulate lactate
- live independently of O2
Mammaliam Dives
- aerobic
- extended time to stay aerobic
What was the purpose of the study of female elephant seals by Le Beouf et al (1987)?
To understand what seals do with their time at sea
What are three possible explanations for the behavior observed in freely diving elephant seals?
Seal behavior involves diving deeply during the day.
1. Feeding
2. Predator avoidance
3. Energy conservation
- Sleep underwater, swim less, or benefit from the dive response
What is the aerobic dive limit and what are its four determinants?
Do female elephant seals reach it when they dive?
How do you know?
Aerobic Dive Limit: the maximum breath-hold possible without any increase in blood lactate concentration during or after the dive.
4 determinants:
1. available O2 stores
2. diving metabolic rate
3. degree of peripheral vasoconstriction
4. rates of lactic acid production and removal
Yes female seals reach it
- know by measuring o2 consumption rates (before and after dive) and lactic acid build up
How do the Po2 and % oxygen levels in air at 20,000 feet compare to those at sea level?
Po2 is lower at 20,000 ft compared to sea level
Percent oxygen is the same
What are three respiratory adaptations that allow geese to tolerate hypoxia?
- Cross current arrangement of blood and air flow
- Blood gas barrier is thinner in birds- less diffusion limitation
- Can hyperventilate so PCO2 can be very low
In the study of Le Beouf et al, how did the time at the surface compare with the time under water?
Spent less time at surface than under water
What are three important characteristics of avian hemoglobin that enhance oxygen transport?
- Blood hemoglobin has high oxygen affinity, or low P50
- Extreme respiratory alkalosis increases their binding affinity of hemoglobin for oxygen
- Body temperature decreases during hypoxia increasing the binding affinity of hemoglobin for oxygen
What are two cardiovascular adaptations that probably allow geese to tolerate hypoxia?
- Birds have larger hearts than mammals
- High cardiac output may prevent perfusion limited
gas exchange
- High cardiac output may prevent perfusion limited
- Maintained blood flow to skeletal muscles with hypoxia
What happens to cerebral blood flow in mammals during hyperventilation and why?
What, specifically, has the bar-headed goose done to overcome this problem?
Result during hyperventilation:
- Pass out due to lower levels of co2 and constriction of vessels in brain
- Blood flow lessened
Goose
- Arterioles are more sensitive to hypoxia and dilate at low arterial PO2
- Do not constrict when CO2 levels are low
- Result is that cerebral blood flow is maintained or increases during hypoxia hypocapnia
List three adaptations that bar-headed geese have at the cellular level that afford hypoxia tolerance
- High capillary density in tissue
- Higher mitochondrial density
- High concentrations of myoglobin in heart and skeletal muscle
Define osmoconformer and osmoregulator. Given one example of each.
Osmoconformer- match their body osmolarity to that of their environment to be isosmotic.
ex: shark
Osmoregulator- maintains and defends a specific body osmolarity.
Ex: Bondy fish
What are the two strategies used by aquatic animals to defend their fluid volumes and composition?
- Excrete dilute urine
- Constantly absorbing ions from the water through the gill epithelial cells
Define the following terms: Isosmotic, hyperosmotic, hypoosmotic, euryhaline, stenohaline.
Hypoosmotic: osmolarity lower than environment
Losing water to environment
Hyperosmotic: higher osmolarity than environment; fish is saltier than environment;
Gaining water from environment
Isosmotic: equal osmolarity as environment
No net loss of water
Euryhaline: tolerate a wide range of external salinities; more plastic; can move betweem
Stenohaline: tolerate a narrow range of external salinities; this or that
Which is more dehydrating for a tetrapod: 0°C air that is saturated with water vapor or 37°C air that has 50% relative humidity?
0 C
How would each of the following affect the U/P ratio?
i. A freshwater bony fish compared to a seawater bony fish.
Freshwater bony fish: U/P < 1 vs. seawater bony fish U/P=1
How would each of the following affect the U/P ratio?
ii. A shark compared to a seawater bony fish. (size)
Shark: U/P < 1 vs. seawater bony fish U/P=1
How would each of the following affect the U/P ratio?
A frog that ingests 5 g of NaCl compared to a similar sized mammal that ingests the same amount of NaCl.
Frog U/P = 1 vs similar sized mammal U/P < 1
Rank the following metabolic fuels in order of decreasing water conservation: carbohydrate, lipids, protein with urea production, and protein with uric acid production.
Lipids, carbohydrates, proteins w uric acid, protein with urea product
LCA
What are the two principal mechanisms that allow kangaroo rats to live without drinking as adults?
- Thicker renal medullae and longer loop of henle
- Other things they do - they eat seeds that are lipid rich and forage at night
How does a cell react, physiologically, when placed in a hyperosmotic solution? How about a hyposmotic solution?
- Hyperosmotic: shrinks and die
- Hypoosmotic: swells and burst
What is the main osmoregulatory problem that a freshwater bony fish faces?
How about seawater bony fishes?
What are the physiological mechanisms that each uses for dealing with them?
Freshwater
- hyperosmotic relative to their environment, so they are saltier than water and will constantly gain water passively across the skin, gills, and gut (lack of Na reabsorption)
- Constantly produce a dilute urine and absorb ions from the water through the gill epithelial cells. They always pee
Seawater
- hypoosmotic relative to their environment, so water is saltier and will constantly lose water passively across the skin, gills, and gut (risk of dehydration)
- Constantly drink seawater and excrete ions at the gills and into isosmotic urine
What overall strategy do marine teleost fishes use to maintain their fluid volume and to manage their salt concentrations?
What is the overall strategy for freshwater fishes?
Seawater - drink seawater to replace large amount of water passively being lost; kidneys and gills will excrete excess salt.
Freshwater - constantly pee to get rid of large amount of water passively being gained; gill epithelial cells must absorb a lot of Na
What is chloride cell
and how does it relate to osmoregulation in fish?
a mitochondria-rich cell in teleost fish gills, which transports mostly Cl, but some Na too
number and expression of these cells can can change depending on the fish’s osmolarity to water (in low mineral water, more cells, to increase Na+ reabsorption)
How have non-amphibian tetrapods (amniotes) solved the problem of dehydration?
- Cutaneous gas exchange in amphibians makes the skin thin and high in perfusion of capillaries to expel CO2 via diffusion.
- Amniotes developed a better ventilatory system (by developing coastal breathing and removing restraint to expel CO2 via cutaneous gas exchange) that allowed integument to thicken and harden (impermeable to water).
What comprises obligatory water less in an animal?
breathing, urine, feces
How does body size affect water loss?
Describe three specific adaptations that rodents utilize to address this?
As body size decreases, water loss increases because their mass-specific metabolic rate is higher. Which increases their susceptibility to water loss through evaporation from the skin and respiratory surfaces
- They must breathe more to fulfill high metabolic rate, so they lose more water via respiration
- more nocturnal activity (when it’s cooler)
- Longer loops of henle– concentrated urine and high kidney efficiency
What is the amphibian water balance response?
What hormone is most important, where is it secreted, what are its target tissues,
and mechanisms of action?
Amphibian water balance response: amphibians that cannot access much water must conserve as much water as possible
hormone– antidiuretic hormone (ADH) / vasopressin
produced– posterior pituitary gland
target– distal nephron
If the animal lacks an adequate water source, its body osmolarity will increase, triggering ADH production. High ADH makes the tubule wall permeable to water. As NaCl is reabsorbed, water will follow, resulting in an isosmotic salt and water reabsorption. The best the animal can do is produce urine that has the same osmolarity as its plasma.
What is glomerular filtration rate
and what two regulated factors determine it?
The glomerular filtration rate (GFR): rate at which fluid moves from the glomerulus into the Bowman’s capsule
- Hydrostatic pressure / blood filtration pressure
- resistances of vessels / filtration coefficient
Which portion of the nephron is responsible for absorbing the bulk of the filtered water and solutes?
Proximal Convoluted Tubule
Which portion of the nephron is regulated hormonally?
Describe the changes that occur.
distal portion, controlled by ADH (aka vasopressin)
- increases the permeability of the distal nephron to H2O
- decreases glomerular filtration rate in amphibians,
- increased NaCl reabosorption in the renal tubules and the urinary bladder
- less, high conc urine
Which portion of the nephron is only present in mammals?
What are the consequences for the U/P ratio because of it?
How does this structure function to achieve this?
Loop of Henle
U/P > 1 due to countercurrent multiplication
Water moves out of descending limb; solutes move out of ascending limb – this multiplies over time to create gradient and in the end, to produce a very concentrated urine
Which portion of the nephron is responsible for determining the final concentration of water and solutes in the urine?
Distal portion (distal tubule and collecting duct)
Describe the mechanism by which an aglomerular kidney (no glomerular) still manages to excrete solutes?
- The solutes are actually transported into the lumen of the tubule, and water follow
- When water flows in, there will be a hydrostatic pressure created that provides the force to excrete the fluid.
What are the three chemical forms of nitrogenous wastes excreted by animals? Indicate which forms are used by fishes, amphibians, reptiles, mammals, and birds.
Ammonia – crocodiles and alligators (reptiles), fishes
Urea - mammals
Uric Acid – birds, reptiles
Describe why gravity is such a problem in regard to blood distribution and interstitial fluid accumulation in giraffes.
The pull of gravity combined with the very tall build of giraffes leads to:
High capillary pressures (esp. in legs)
Lowering their head causes greater fluid flow from the capillaries to the interstitial space.
Excessive buildup can cause edema.
Pooling of blood and fluid in the extremities.
Additionally, the heart must do more work to pump blood towards the head, against the force of gravity.
How do giraffes manage to insure adequate blood flow to their brain?
giraffe blood pressure is 2x that of humans, producing a greater force against gravity
in relation to venous function, their tight skin layer, along with muscle pumps move fluid upwards against gravity
How do they prevent high intravascular pressures when lowering their head to feed from the ground?
greater density of valves in the veins at the top of the neck than those in the lower part
These valves are made up of connective tissue, preventing blood backflow when lowering their heads
This allows jugular vein pressures to be higher at the base of the skull versus the base of the neck.
As the distance above the heart decreases, so does the jugular vein pressure, preventing high blood flow to the head when lowering to the ground.
What did their measurements of interstitial and colloid osmotic pressure tell them?
What specific adaptations do giraffes have to prevent edema in their legs and feet?
Measurements
- capillary colloid osmotic pressure is the same everywhere
- interstitial fluid pressure higher in the foot than anywhere else
Adaptations: To prevent edema they have a muscle pump to return blood/ fluid to the heart and tight skin to act as an antigravity suit:
- rely on the muscle pump to return blood and fluid to the heart
- rely on tight skin to act as an anti-gravity suit
Define the following and provide one vertebrate example of each: poikilothermy, homeothermy, heterothermy, endothermy, ectothermy.
poikilothermy
- body temperature is determined by the environment
- icefishes
homeothermy
- “warm-blooded”; maintain their body temperatures around 37
- African Elephant
(temporal) heterothermy
- also “warm-blooded”, but allows its body temperature to fall
- 13-lined ground squirrel
endothermy
- regulating heat product to enable their bodies of having a temperature greater than the environment
- Tuna
ectothermy
- acclimating to a temperature in the environment
- lizards
Why is evaporative cooling such an effective way of dumping heat?
birds and mammals have high metabolic rates, so their respiratory evaporation sends out wet air (H2O)
high heat of vaporization
Why is the observed distribution of the body temperatures measured in living lizards so much narrower than those measured in an identical, non-living model?
Ectotherms can behaviorally thermoregulate. They can go in the shade/sun or constrict/dilate their blood vessels
In simple terms, what does Q10 describe?
What is the actual numerical value for biochemical processes, generally?
The fold change in reaction rate or process for a 10 degree change in temperature.
Human Q10 is around 2-3, but its temperature dependent. As our body temperature lowers, Q10 increases.
How is metabolic rate affected by body temperature?
Why?
sped up during warmer temperatures with reaction rates increasing and and affecting metabolic rate logarithmically
higher temp = more heat in system = lots more happening = stuff happening faster = more collisions = chaos = more reactions = basically MORE, just cause u closer to reaching AE. includes all reactions involved w ATP consumption and production
How would cold acclimation affect metabolic rate in a lizard?
What is the function of this acclimation response?
cold acclimation would lead to a higher metabolic rate in the cold
sustain their life
Describe the effects of temperature on enzyme activities. How is it that different animals living in different thermal environments all maintain similar enzyme-substrate affinities for many different enzymes?
- increasing temperature leads to decreasing enzyme-substrate affinity
- changes in makeup of the enzyme / post translational modification
- changes in amino acid structures
(already in animal)
How does temperature affect the fluidity of plasma membranes?
What is the consequence the change?
What is homeoviscous adaptation and how is it adaptive?
as temperature increases, fluidity increases
consequence: if there was a sudden change in temperature, proteins in the cell membrane would be hurt, as there would be an increase in protein and ion movement across a membrane in higher temperatures, and a decrease in lower temperatures
homeoviscous adaptation: It is the adaptation of the cell membrane to maintain a relatively constant membrane fluidity. It changes based on temperature, where the concentrations of saturated and unsaturated lipids change to increase or decrease fluidity relative to the temperature
- the alkane is less fluid. As the temperature falls, the fluidity falls.
- Can be advantageous when temperatures are low
How does increasing insulation affect the thermoneutral zone?
How does decreasing it affect it?
increasing insulation shifts the thermoneutral zone down and lowers critical temp as they cannot eliminate heat as well
decreasing insulation shifts the thermoneutral zone to up (can bear higher temps) to increase critical temperatures
Describe the basic anatomical arrangement of a countercurrent heat exchanger and how it conserves heat in the leg of the European rook.
their leg has a specialized vascular anatomy so that countercurrent heat exchange can occur. The artery is at the center, with the veins surrounding it in a countercurrent heat exchange arrangement.
Heat is transferred from the artery to the venous blood that is returning from the extremity. The cooling of arterial blood going to the extremity lowers the temperature gradient between the environment and the limb, thus conserving heat.
Why does dehydration become a major problem for endotherms in extremely warm climates?
How have camels solved this problem?
Dehydration is a major problem for endotherms in extremely warm climates because their principle means of losing heat is losing water (panting or sweating)
In camels:
deep cycling of body temperature allows them to conserve water.
they can store heat and dump it at night
(how they are adapted to the cold drop in the desert)
Despite the fact the blood leaving the gills in tuna is the same temperature as the water flowing across them, their swimming muscles are warmer than the water. Explain how this is achieved.
Tunas have countercurrent heat exchange in their red swimming muscle
Metabolic heat is retained in the exercising muscle, which is always contracting because tuna are always swimming. Thus, there is a lot of heat production
