animanimal phys-- exam 2 Flashcards
What hypothesis is SECOR testing,
and why are they testing it
Since maintaining the gut is energetically expensive, snakes can rapidly upregulate and downregulate their gut endothelium
Snakes have an abnormal metabolic rate, where they do not have to eat for long periods of time, and Secor wants to understand why
What happens to oxygen consumption rate after a meal in rattlesnakes?
How does this compare to the oxygen consumption rate of a typical mammal after a meal?
What accounts for these differences in oxygen consumption rate?
O2 consumption rate increases and reaches its maximum within the first 2-3 days after ingestion. This increases before digestion is completed.
Mammal O2 consumption rates are 25-50%, rattlesnakes is 8-10 fold this.
By day 2, the metabolic rate is increased by 7.8x the resting metabolic rate. Rattles increase this metabolic rate by digestion alone, whereas mammals can only reach this level through exercise.
Differences in the digestion of meals, motility, upregulation, and growth of tissue account for this. More transporters in the gut results in more ATP used and more O2 flux.
How does the transport capacity of amino acids compare to that of glucose in the small intestine of the rattlesnake?
Why does this make sense?
Higher amino acid uptake than glucose uptake, particularly in the anterior portion of the intestine.
The snake is digesting a mouse which is protein dense, and proteins are made up of amino acids. Also, there is not much need for glucose uptake, as a snake’s diet does not contain much glucose in it.
What morphological changes occur in rattlesnake intestine after feeding?
What might these changes serve?
- The anterior gut has a higher plasticity compared to the distal portion.
- The anterior portion’s mucosa changes to be very big within a couple of days before returning back to normal after digestion.
- There is little change in the distal mucosa, thus increasing intestinal uptake capacity.
- As the small intestine’s longitudinal folds get thicker, mucosal surface area is increased, which allows for more transporters, thus increasing transport capacity.
What happens to the heart of digesting Burmese pythons after it ingests a large meal?
What is the physiological function of these changes?
Burmese pythons experience cardiac hypertrophy to support digestion. This causes VO2 and heart mass to increase.
Through this, there is increased blood flow and cardiac output, bringing more O2 to the tissues. This allows pythons to increase their metabolic rate by 40x, which helps facilitate the demands of digestion
Pythons increase Vo2 (metabolic rate) 40x. Increase wet mass of organs like the heart. Increase heart mass to increase blood flow and metabolic rate to facilitate demands of digestion. Increased expression of cardiac myosin heavy chain. Mass-specific DNA concentration is decreased. Function of increased in blood flow to facilitate oxygen delivery requirement to tissues, which consume enormous amounts of oxygen in the gut.
How do we know that the changes that were seen resulted from hypertrophy and not hyperplasia ?
no change in in total protein, RNA, or myofibrillar concentrations between fasting and digesting. However, there was a decrease in mass-specific DNA concentrations, as well as an increased expression of cardiac myosin heavy chain
Symmorphosis
A proposed principle or idea of animal design that drives hypothesis-making based on anatomy and physiology. It claims that animals are built to have exactly what they need to survive– no more, no less
the reasoning behind this is that it is energetically wasteful to have more than whats needed, and that animals would incur selective penalty for maintaining structures that are in excess to their demands.
What question were Taylor and Weibel attempting to answer in their study?
What were their hypotheses?
Is the mammalian respiratory system optimally designed and support symmorphosis and the O2 flow requirements
hypothesized that the structural design is:
- a rate limiting factor for O2 at each level
- optimized
- adaptable
Describe Taylor and Weibel’s experimental approach, including the physiological parameters they measured and the two study systems they investigated them in?
A comparative approach:
1. Investigated the O2 transport of a system on animals with similar body masses, but with differing aerobic performances
- same size, but energetic vs lazy = dog vs sheep, wild vs domesticated, etc
- investigates the O2 transport system in different sized mammals between 0.5-250 kg
- smaller animals have higher metabolic rates
The tools
- Allometry: measured structural parameters such as alveolar SA, mitochondrial V, diffusion capacity, Vo2 max
What did they conclude (T and W)
- animals are built reasonably, with an economical design that is applicable to all levels
- all of the variables they measured were consistent with the principle of symmorphosis, though most did not scale with body mass in the predictable way
(ex: bigger animals have excess lung capacity and cardiac potential)
Do Lindstedt and Jones agree with the conclusions of Taylor and Weibel? Why or why not?
Not really. Cause the O2 transport system could not be built optimally as it requires 2 assumptions: 1. organ system serves a single purpose; 2. organ system is constantly under natural selection
- What if a structure had multiple functions? What function should be optimized?
- Why can’t adequate be adequate? Can adequate be optimal?
- Is it testable?
Why are Lindstedt and Jones concerned about tautology in the context of symmorphosis?
Work by T and W came out all at once, and in 9-10 papers supporting the same symmorphosis theory. This led to a peak in the use of this hypothesis. This raises a concern of the replicability / application of this hypothesis as the majority of proof at the time was just from 2 authors
What are Garland’s primary criticisms of symmorphosis?
- organisms are not “designed” and natural selection is not “engineered”
- optimal design is limited by the starting material
- there is little empirical evidence supporting energetic efficiency as a “goal” of selection
- environments change faster than animals
- all animals are equally likely to be killed by stochastic events
- genetic drift will cause deviations from optimality, when the trait isn’t under strong selection
- behavior evolved more rapidly than physiology, and may have more influence over what animals can and cannot do
- sexual selection can lead to irrational animal designs
sexual behavior environments serve specific energetic genital designs
What is an animal’s metabolic rate
the rate at which an animal converts chemical energy into work and heat
it determines how much food an animal needs and is a reflection of the activity of all its physiological processes and defines the relationship an animal has with its environment
where does metabolic heat come from
metabolic processes in the mitochondria
Specifically, the heat loss of every transfer of energy from the breaking of covalent bonds
(“38% of the chemical energy is transferred from covalent bonds in glucose to covalent bonds in ATP; 62% is lost as heat.”)
What is the difference between direct calorimetry and indirect calorimetry?
Direct:
- metabolic heat production is measured directly (how much heat is needed to melt a specific amt of something)
- measures heat production
Indirect:
- uses another parameter as a proxy for metabolic heat production (ex: respirometry)
- estimates energy expenditure based on respiration
What is the respiratory exchange ratio
and what is its normal value in a typical animal?
How is it affected by metabolic fuel utilization?
- Vco2 / Vo2 = CO2 production / O2 consumption
- 0.8
- these rates will correlate to metabolic heat production
- physical activity level and environmental temperature, type of meal, body size, etc
- Differing fuel = differing amounts of energy produced
- Amount of CO2 produced relative to the amount of energy generated varies on the metabolic fuel that you use
Describe the relationship between body mass and metabolic rate.
How does this relationship compare between endotherms and ectotherms?
larger mass = lower metabolic rate
this holds truth for both endotherms and ectotherms.
The difference in metabolic rate alone lies in the fact that endotherms typically have a higher rate, as they are required to use more energy to maintain their body temperatures, whereas an ectotherm depends on external sources
The exponents associated with the exponential curve are similar to one another, showing the relationship is relatively the same in endotherms and ectotherms.
Describe why gravity is such a problem in regard to blood distribution and interstitial fluid accumulation in giraffes. (hargens)
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.
- 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.
Their muscle pumps and tight skin layer move fluid upwards against gravity.
How do giraffes prevent high intravascular pressures when lowering their head to feed from the ground?
- they have more veins at the top of their neck than those in the lower part
- connective tissue in the neck squeezes down on the blood in the veins, preventing blood backflow when lowering
- 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 Hargens 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 is higher in the foot than anywhere else
- there are many valves in the veins at the top of the neck and bottom of feet [-7 mmHg pressure in neck (resorptive) and 88-152 mmHg pressure in leg (filtration)]
- arterial pressure decreases going up the neck, and increases going down
- venous pressure is higher at the top of the neck than at the bottom of the leg
- high variability in blood pressure at the foot
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 muscle pump to return blood and fluid to the heart
- rely on tight skin to act as an anti-gravity suit
Describe the physiological problem Seymour and Lillywhite were trying to elucidate.
- recent ventricular data on sauropods seems disadvantageous for the endothermic animal. To accommodate, their mean arterial pressures would have had to exceed 700 mmHg in order to perfuse the head. Is this physiologically and/or anatomically possible ?
- could the sauropod lift its head several stories above their heart, even tho the species is much taller than the giraffe ? If so, could this have been done if they were endotherms?
What did Seymour and Lillywhite conclude about the likelihood that sauropods were endothermic and could lift their heads?
What led them to this conclusion?
If they were endotherms they prob couldn’t lift their heads erect above their heart unless they had the metabolic rate of an ectotherm
- Would need 700mmHg blood pressure to move the blood to their brains
- By Laplace’s principle; ventricle would be 70% of the heart’s mass. (allometric relationship)
- the left ventricle would be 2 tons, requiring more energy to deform the heart than to propel the blood.
What alternatives to cardiac hypertrophy did Sey and Lilly believe allow sauropods to solve their cardiovascular challenge?
smaller end-diastolic volumes and stroke volumes, which would be achieved by:
- higher heart rate
- lower cardiac output (by 10-20 %) requirements (make them ectotherms by lowering their metabolism)
- smaller stroke volume (0.02% bm) and heart rate (0.04% bm)
for 1/2 endothermic level, 700 mmHg blood pressure is possible with a heart that is 1.3% bm (like a giraffe)
List four ways an animal may use to achieve homeothermy.
- behavior
- blood flow distribution
- insulation
- coloration
- cellular heat production
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