final exam

Question 1

Why can’t a trout breathe air? Please answer this question in terms of the physical properties water and air

Answer 1

There is more concentration of oxygen in air and less in H2O

Question 2

Why can’t a trout breathe air in terms of ventilatory mechanics

Answer 2

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

Question 3

Why can’t a trout breathe air in terms of respiratory anatomy

Answer 3

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.

Question 4

Define hypoxia, normoxia, and hyperoxia.

Answer 4

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

Question 5

What about the physical and biological environments requires pupfish to be so hypoxia-tolerant

Answer 5

as salinity and temperature increase, gas solubility decreases, according to Henry’s law

Question 6

Solution A: O– 100; PO2– 50
Solution B: O– 50; PO2– 100

which will have higher osmolarity

Answer 6

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

Question 7

Solution A: O– 100; PO2– 50
Solution B: O– 50; PO2– 100

which will have a higher temperature

Answer 7

Solution B

Oxygen saturation is the lowest in warmer water, because by Henry’s Law, gas solubility decreases as temperature increases

Question 8

Solution A: O– 100; PO2– 50
Solution B: O– 50; PO2– 100

which is most like blood

Answer 8

Solution B

Blood’s Po2 range is within 75-100 mHg, which aligns with Solution B’s Po2

Question 9

Solution A: O– 100; PO2– 50
Solution B: O– 50; PO2– 100

which has the higher O2 solubility

Answer 9

Solution A

solubility = [Gas] / Pgas
= 100/50 = 2

2 is higher than 1/2 in Sol B

Question 10

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?

Answer 10

B - > A

There is a pressure gradient created, as B has a higher Po2 than A

Question 11

Describe the basic model of how a fish ventilates its gills. (summer and ferry)

Answer 11

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

Question 12

methods (summer and fairy– fish gill ventillation)

Answer 12

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

Question 13

purpose (summer and fairy)

what about the status quo ?

Answer 13

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”

Question 14

What finding challenged the accepted model of gill ventilation in fishes?

What are the implications for gas exchange?

Answer 14

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

Question 15

What is costal breathing, who uses it, and for those who don’t, what do they do ?

Answer 15

costal breathing: expansion and contraction of the lung cavity through movement of the ribs

use it: birds, mammals, lizards

crocs and turtles

Question 16

what do crocs and turtles do instead of costal breathing

Answer 16

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.

Question 17

What is the arrangement of air flow relative to blood flow called in the bird lung?

Answer 17

the arrangement of airflow relative to blood is cross current exchange

Question 18

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)

Answer 18

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”

Question 19

what are two other differences between bird and non-croc reptile lungs

Answer 19

• 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

Question 20

What is the purpose of the study of Bretz and Schmidt-Nielsen?

Answer 20

investigate the respiratory system of the ducks.

understand the patterns of airflow through the respiratory system during different phases of the ventilation cycle

Question 21

Describe the design of their experiment (Bretz and Schmidt)

Answer 21

• 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

Question 22

What was the most important finding of the study by Bretz and Schmidt-Nielsen?

Answer 22

the avian respiratory system functions as a two cycle pump

Question 23

Describe how air flows in the avian respiratory system during a single ventilatory cycle

Answer 23

1. during the 1st cycle of inspiration, fresh air goes to the posterior air sac, and expands
2. during the 1st cycle of expiration, the posterior air sacs shrink and inspired gas moves from the posterior air sacs, pushing through the lung
3. during the 2nd cycle of inspiration, after passing through the lung, has fills the anterior air sac, which expands
4. 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

Question 24

What conventional wisdom are Farmer and Sanders challenging

Answer 24

alligators are tidal, coastal breathers like humans. They change the shape of their chest wall and volume of lungs.

Question 25

What hypothesis are F and S testing in their study?

Answer 25

Airflow in alligator lungs is unidirectional

Question 26

what is the evolutionary significance of farmer and sanders

Answer 26

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

Question 27

What did their experiments show? Do they make sense? Why?

Answer 27

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.

Question 28

why are the findings of farmer and sander considered controversial

Answer 28

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

Question 29

What factors determine whether or not blood flows from one region of the cardiovascular system to another?

Answer 29

• Pressure gradient: blood flows from high to low pressure
• Resistance: change in vessel diameter can affect this

Question 30

According to Hicks and Wang, what are three possible benefits from having the ability to right to left shunt? Please explain how each works.

Answer 30

1. 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
2. Digestion and Growth: rich blood to parietal cells which promote gastric acid secretion
3. In exercise: more efficient gas exchange

Question 31

Under what circumstances is a R-L shunt observed in reptiles?

Answer 31

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

Question 32

Under what circumstances is a L-R shunt observed in reptiles?

Answer 32

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

Question 33

Describe the cardiac anatomy of a fish and the route that a single erythrocyte takes as it travels through its circulatory system.

Answer 33

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.

Question 34

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?

Answer 34

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.

Question 35

What hypothesis do Farrell and Steffensen test and how do they test it?

What was the outcome of their experiment?

Answer 35

hypothesis: is coronary circulation essential for maximum aerobic performance?
how do they test it

1. surgically placed a silk threat around the coronary artery w/o tightening it, and the fish recovered overnight
2. measured critical swimming speed (Ucrit)
   - Ucrit = Ui + [(ti / tii)(Uii)]
3. tightered the loop on the arteries to ligate them and measure Ucrit again
4. 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)

Question 36

What was the purpose of the Taylor locomotion and cost of transport study

Answer 36

to elaborate the relationship between energetic cost of running and the body weight of mammals

Question 37

Taylor et al’s experimental approach to quantifying the cost of running in mammals

Answer 37

• 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

Question 38

How did the cost of running change with running speed in Taylor et al’s study

Answer 38

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.

Question 39

How did the cost of running change with body size

Answer 39

As animal size decreases, the cost of running increases.

Question 40

What did Taylor et al find when they extrapolated metabolic rate back to zero velocity?

What accounted for this?

Answer 40

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)

Question 41

According to Kram and Taylor, what two factors should directly determine the metabolic cost of running?

Answer 41

1. Cost of supporting the animal’s weight
2. Time course of force generation

Question 42

Why did Kram and Taylor subtract the Vo2 extrapolated back to zero speed?

Answer 42

To determine how much oxygen is consumed (energy required) for just the skeletal muscles during running

Question 43

How does stride length relate to body mass in animals in Kram and Taylor’s study?

Answer 43

Stride length increases with body mass in animals. Lower stride frequencies for larger animals.

Question 44

According to Kram and Taylor’s study, why is running more expensive for smaller animals?

Answer 44

Animals with shorter legs have shorter stride lengths and higher stride frequencies. Therefore, higher transport costs

Question 45

What is the fundamental problem that must be overcome for a muscle to achieve high contraction frequencies?

Answer 45

How does one get extremely high contraction frequencies without temporal summation and tetanus?

Question 46

What three factors determine the frequency with which a skeletal muscle can contract and relax?

Answer 46

1. Fast cross-bridge detachment rates
2. Have a less Ca2+-sensitive troponin isoform
3. Duration of the Ca2+ transient is shorter

Question 47

Why is the toadfish sonic muscle able to achieve higher contraction frequencies than rattlesnake tail-shaker muscle?

Answer 47

• Has a special myosin isoform that has a more rapid detachment rate
• vibration of swim bladder at 200 Hz

Question 48

What are two trade-offs for having the specialized muscles that toadfish and rattlesnakes have with respect to muscle function?

Answer 48

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

1. high frequency contractions are expensive, requiring a lot of ATP (increased mitochondrial volume).
2. Does not generate much force (reduced myofibril volume)

Question 49

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?

Answer 49

There is a temperature independent mechanism for metabolic depression

Question 49

What are two mechanisms used by hummingbirds to achieve simultaneous high contraction frequencies, force production, and fatigue resistance in their flight muscles?

Answer 49

To beat zero-sum game (get high frequency, force, and fatigue resistance in muscle)

1. increase operating temperature of a muscle (enables them to achieve high rates of muscle contraction + force)
2. increase the packing of the mitochondrial cristae (get the most out of ATP)

Question 49

What are the differences between hibernation, aestivation, and daily torpor?

Answer 49

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

Question 49

Why is torpor and hibernation considered to a strategy that conserves energy?

Why do small animals benefit more?

Answer 49

• 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

Question 49

What did Wilz and Heldmaier conclude about the three dormancy states?

What accounted for any differences seen?

Answer 49

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

Question 49

What was the purpose of the study by Wilz and Heldmaier?

Answer 49

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

Question 50

What conventional view of hibernation were Toien et al challenging in their study of bear hibernation?

Answer 50

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?

Question 51

What was the most important finding of the study?

Answer 51

• 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)

Question 52

State four commonalities between bears and rodents in regard to hibernation.

Answer 52

1. Decreased metabolic rate
2. Reduced heart rate
3. no diurnal body temperature cycle
4. do not eat or drink for 6 months

Question 53

What are two important differences between hibernation in bears versus rodents?

Answer 53

In bears…
1. body temperature falls much less
2. no interbout arousals

Question 54

What are the two primary strategies for surviving subzero temperature called?

How do they differ from one another? Give one example of each strategy.

Answer 54

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

Question 55

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?

Answer 55

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

Question 56

What is the primary cause of cellular death when an animal freezes?

How do hatchling turtles and wood frogs prevent this from happening?

Answer 56

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

Question 57

What makes a turtle’s pond anoxic during the winter?

Answer 57

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)

Question 58

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?

Answer 58

Normoxic: Lactic acid and atp

Anoxic: Co2 atp water

Fuel: glycogen

Organ: liver

Question 59

What are the three primary adaptations that allow turtles to survive anoxia?

Answer 59

1) Metabolic depression
2) Extremely large glycogen stores
3) Extremely large buffering capacity

Question 60

What are three ways that a turtle depresses its metabolism?

Answer 60

1. Reductions in cardiovascular activity..
2. The animal becomes dormant.
3. Downregulation of glycolytic enzymes.
4. Decreases in protein synthesis

• Arrest ion channels and translation
• Decreases in Na, K and Ca conductance
• Reduces ATP expenditure on ion pumping.

Question 61

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?

Answer 61

• 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

Question 62

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?

Answer 62

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

Question 63

What is the main metabolic fuel supporting energy production during anoxia in goldfish and crucian carp?

Answer 63

Glycogen

Question 64

Describe how hypoxia leads to neuronal death in hypoxia-sensitive neurons. (Bickler, Buck, Nilsson)

Answer 64

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

Question 65

How do the ion channels in turtle neurons respond to hypoxia?

What is this physiological response called?

Answer 65

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

Question 66

What neurotransmitter activates NMDA receptor channels?

What ion does it conduct?

What happens to this ion channel in turtle neurons during anoxia?

Answer 66

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

Question 67

What are two mechanisms by which NMDA receptor channels are down-regulated in hypoxia-tolerant neurons?

Answer 67

1. Reduce conductance of NMDA receptors (ion channel arrest)
2. Phosphorylate the channels (Post-translational modifications). Change the composition of the receptor

ATP consumption rates are lower, preventing excitotoxicity

Question 68

What other intracellular signaling molecule is likely involved in coordinating the responses of turtle neurons to hypoxia?

Answer 68

Calcium

Question 69

How do the behavioral responses to anoxia compare between crucian carp and turtles?

Answer 69

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

Question 70

What happens to cerebral blood flow during anoxia in crucian carp and what function does this change serve?

Answer 70

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

Question 71

What happens to brain GABA levels during anoxia in crucian carp and what function does this change serve?

Answer 71

they are elevated to calm neural activity, thus avoiding excitotoxicity

Question 72

What important anoxia tolerance strategy is used less by the crucian carp brain but is used in the turtle brain?

Answer 72

Crucian carp do not show ion channel arrest

Question 73

What are the two basic problems an animal faces when it dives to extreme depths?

Answer 73

1. O2 availability
2. The Bends (decompression sickness)

Question 74

What causes The Bends and how do diving mammals avoid it?

Answer 74

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

Question 75

What are two adaptations of diving mammals’ oxygen transport system that allows it to have extended aerobic dive times?

Answer 75

1. Large O2 stores in myoglobin
2. Greatest percentage of total oxygen store is in blood

Question 76

What circulatory changes occur during diving and what functions do they serve for the animal? How do they relate to dive duration?

Answer 76

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

Question 77

What is the oxygen debt and how does it relate to lactate production and oxygen consumption?

Answer 77

• 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

Question 78

What is the major difference between diving turtles and marine mammals in how they adapt to extended apneic periods?

Answer 78

Turtle Dives
- anaerobic
- accumulate lactate
- live independently of O2

Mammaliam Dives
- aerobic
- extended time to stay aerobic

Question 79

What was the purpose of the study of female elephant seals by Le Beouf et al (1987)?

Answer 79

To understand what seals do with their time at sea

Question 80

What are three possible explanations for the behavior observed in freely diving elephant seals?

Answer 80

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

Question 80

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?

Answer 80

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

Question 80

How do the Po2 and % oxygen levels in air at 20,000 feet compare to those at sea level?

Answer 80

Po2 is lower at 20,000 ft compared to sea level
Percent oxygen is the same

Question 80

What are three respiratory adaptations that allow geese to tolerate hypoxia?

Answer 80

1. Cross current arrangement of blood and air flow
2. Blood gas barrier is thinner in birds- less diffusion limitation
3. Can hyperventilate so PCO2 can be very low

Question 80

In the study of Le Beouf et al, how did the time at the surface compare with the time under water?

Answer 80

Spent less time at surface than under water

Question 80

What are three important characteristics of avian hemoglobin that enhance oxygen transport?

Answer 80

1. Blood hemoglobin has high oxygen affinity, or low P50
2. Extreme respiratory alkalosis increases their binding affinity of hemoglobin for oxygen
3. Body temperature decreases during hypoxia increasing the binding affinity of hemoglobin for oxygen

Question 81

What are two cardiovascular adaptations that probably allow geese to tolerate hypoxia?

Answer 81

1. Birds have larger hearts than mammals
   
   • High cardiac output may prevent perfusion limited
     gas exchange
2. Maintained blood flow to skeletal muscles with hypoxia

Question 82

What happens to cerebral blood flow in mammals during hyperventilation and why?

What, specifically, has the bar-headed goose done to overcome this problem?

Answer 82

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

Question 83

List three adaptations that bar-headed geese have at the cellular level that afford hypoxia tolerance

Answer 83

1. High capillary density in tissue
2. Higher mitochondrial density
3. High concentrations of myoglobin in heart and skeletal muscle

Question 84

Define osmoconformer and osmoregulator. Given one example of each.

Answer 84

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

Question 85

What are the two strategies used by aquatic animals to defend their fluid volumes and composition?

Answer 85

1. Excrete dilute urine
2. Constantly absorbing ions from the water through the gill epithelial cells

Question 86

Define the following terms: Isosmotic, hyperosmotic, hypoosmotic, euryhaline, stenohaline.

Answer 86

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

Question 87

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?

Answer 87

0 C

Question 88

How would each of the following affect the U/P ratio?
i. A freshwater bony fish compared to a seawater bony fish.

Answer 88

Freshwater bony fish: U/P < 1 vs. seawater bony fish U/P=1

Question 89

How would each of the following affect the U/P ratio?
ii. A shark compared to a seawater bony fish. (size)

Answer 89

Shark: U/P < 1 vs. seawater bony fish U/P=1

Question 90

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.

Answer 90

Frog U/P = 1 vs similar sized mammal U/P < 1

Question 91

Rank the following metabolic fuels in order of decreasing water conservation: carbohydrate, lipids, protein with urea production, and protein with uric acid production.

Answer 91

Lipids, carbohydrates, proteins w uric acid, protein with urea product

LCA

Question 92

What are the two principal mechanisms that allow kangaroo rats to live without drinking as adults?

Answer 92

1. Thicker renal medullae and longer loop of henle
2. Other things they do - they eat seeds that are lipid rich and forage at night

Question 93

How does a cell react, physiologically, when placed in a hyperosmotic solution? How about a hyposmotic solution?

Answer 93

• Hyperosmotic: shrinks and die
• Hypoosmotic: swells and burst

Question 94

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?

Answer 94

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

Question 95

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?

Answer 95

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

Question 96

What is chloride cell

and how does it relate to osmoregulation in fish?

Answer 96

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)

Question 97

How have non-amphibian tetrapods (amniotes) solved the problem of dehydration?

Answer 97

• 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).

Question 98

What comprises obligatory water less in an animal?

Answer 98

breathing, urine, feces

Question 99

How does body size affect water loss?

Describe three specific adaptations that rodents utilize to address this?

Answer 99

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

1. They must breathe more to fulfill high metabolic rate, so they lose more water via respiration
2. more nocturnal activity (when it’s cooler)
3. Longer loops of henle– concentrated urine and high kidney efficiency

Question 100

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?

Answer 100

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.

Question 101

What is glomerular filtration rate

and what two regulated factors determine it?

Answer 101

The glomerular filtration rate (GFR): rate at which fluid moves from the glomerulus into the Bowman’s capsule

1. Hydrostatic pressure / blood filtration pressure
2. resistances of vessels / filtration coefficient

Question 102

Which portion of the nephron is responsible for absorbing the bulk of the filtered water and solutes?

Answer 102

Proximal Convoluted Tubule

Question 103

Which portion of the nephron is regulated hormonally?

Describe the changes that occur.

Answer 103

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

Question 104

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?

Answer 104

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

Question 105

Which portion of the nephron is responsible for determining the final concentration of water and solutes in the urine?

Answer 105

Distal portion (distal tubule and collecting duct)

Question 106

Describe the mechanism by which an aglomerular kidney (no glomerular) still manages to excrete solutes?

Answer 106

1. The solutes are actually transported into the lumen of the tubule, and water follow
2. When water flows in, there will be a hydrostatic pressure created that provides the force to excrete the fluid.

Question 107

What are the three chemical forms of nitrogenous wastes excreted by animals? Indicate which forms are used by fishes, amphibians, reptiles, mammals, and birds.

Answer 107

Ammonia – crocodiles and alligators (reptiles), fishes

Urea - mammals

Uric Acid – birds, reptiles

Question 108

Describe why gravity is such a problem in regard to blood distribution and interstitial fluid accumulation in giraffes.

Answer 108

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.

Question 109

How do giraffes manage to insure adequate blood flow to their brain?

Answer 109

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

Question 110

How do they prevent high intravascular pressures when lowering their head to feed from the ground?

Answer 110

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.

Question 111

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?

Answer 111

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

Question 112

Define the following and provide one vertebrate example of each: poikilothermy, homeothermy, heterothermy, endothermy, ectothermy.

Answer 112

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

Question 113

Why is evaporative cooling such an effective way of dumping heat?

Answer 113

birds and mammals have high metabolic rates, so their respiratory evaporation sends out wet air (H2O)

high heat of vaporization

Question 114

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?

Answer 114

Ectotherms can behaviorally thermoregulate. They can go in the shade/sun or constrict/dilate their blood vessels

Question 115

In simple terms, what does Q10 describe?

What is the actual numerical value for biochemical processes, generally?

Answer 115

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.

Question 116

How is metabolic rate affected by body temperature?

Why?

Answer 116

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

Question 117

How would cold acclimation affect metabolic rate in a lizard?

What is the function of this acclimation response?

Answer 117

cold acclimation would lead to a higher metabolic rate in the cold

sustain their life

Question 118

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?

Answer 118

• 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)

Question 119

How does temperature affect the fluidity of plasma membranes?

What is the consequence the change?

What is homeoviscous adaptation and how is it adaptive?

Answer 119

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

Question 120

How does increasing insulation affect the thermoneutral zone?

How does decreasing it affect it?

Answer 120

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

Question 121

Describe the basic anatomical arrangement of a countercurrent heat exchanger and how it conserves heat in the leg of the European rook.

Answer 121

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.

Question 122

Why does dehydration become a major problem for endotherms in extremely warm climates?

How have camels solved this problem?

Answer 122

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)

Question 123

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.

Answer 123

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