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What are two ways seals can meet metabolic demands for O2 underwater?

1. Change oxygen storage in body

2. Diving reflex

How does oxygen carrying capacity of blood increase for diving animals?

1. Hematocrit increase → more RBC in circulation

2. Hemoglobin increase → will increase O2 capacity

3. Increase blood volume per body mass → increases total amount of O2 that can be delivered to tissues

4. Myoglobin increase → has higher affinity to take up O2 than hemoglobin, allowing it to extract more O2 from the blood

Is dive duration impacted by oxygen carrying capacity?

No, oxygen stores cannot predict diving duration. Will only speak to blood’s ability to carry oxygen

How is the diving reflex triggered?

Exposure to cold water to face and holding breath → think of waterboarding seals

What is the diving reflex?

Reduction of O2 consumption in three ways:

1. Circulatory adjustment

2. Reducing metabolic rate

3. Changing behavior of diving

How will diving reflex change circulatory?

Decrease HR and cardiac output will hyperstimulate PNS (when HR decreases, PNS increases). This is done to cut off the blood flow to certain organs to limit O2 usage.

Increase in TPR = vasoconstriction to nonessential organs. This means the spleen will constrict and release RBS, increasing hematocrit

dec CO = dec HR = inc PNS = inc TPR = maintain BP

How will diving reflex reduce metabolic rate?

Decrease in metabolism due to vasoconstriction. Tissues will cool off after O2 is shut off, meaning that the tissues will rely on myoglobin stores for aerobic resp. Once that is done, will anaerobic and release lactic acid as a byproduct.

How will diving reflex change behavior?

Gliding is used over swimming down. Torpedoing is very useful because you don’t use muscles. Sleeping is also good because it decreases metabolism. Limited locomotion prioritized

Is there a metabolic cost to diving?

No with aerobic dives, yes with aerobic dives. Aerobic dives are typically short dives that do not deplete O2.

Yes to anaerobic; dives are longer dives when the seal uses up its O2, causing it to switch to anaerobic (called the aerobic diving limit). The body must produce lactic acid through anaerobic respiratory to maintain metabolism.

What is the aerobic diving limit?

When an animal uses up all of its O2 from diving and must switch over to anaerobic conditions.

What happens to lactic acid concentrations when a seal resurfaces?

The lactic acid produced from anaerobic respiration must be released, which drives the concentration of the blood up. Seals must stay at the surface to regulate to the original levels of lactic acid and concentration, as this allows the conversion of lactic acid to pyruvate.

How do seals deal with pressure from diving?

Pressure of depth will reduce/collapse the lungs.

How does partial pressure get affected by lung volume?

As lung volume decreases, partial pressure increases. Increased partial pressure will drive gases (nitrogen) into the blood due to Henry’s law.

What is the “bend,” and how does it happen?

Gases will dissolve in the blood, which affects ascension. The bend is a rapid decrease of pressure that causes dissolved gases to release and bubble up, causing decompression sickness.

What are some ways seals prevent decompression sickness?

1. Seals produce pulmonary surfactant that coats alveoli, which decreases the surface tension and makes it easier to reinflate the lungs.

2. Alveolar collapse. Air is forced out of the alveoli and into airways that will not exchange gases. This prevents gases from dissolving in the blood, and thus prevents bubbles from forming.

What are the layers of the GI?

1. Lumen

2. Mucosa: epithelial layer, lamina propria, smooth muscle

3. Submucosa: blood vessels, enteric neurons, glands

4. Muscularis Externa: layers of smooth muscle

5. Serosa: connective tissue

What increases absorption in the GI tract (specifically SI)?

Factors that increase surface area include:

1. Villi and microvilli

2. Folds

3. Vascularized tract (many vessels)

4. Lympatic ducts

Which enzymes break down food, and where are they released?

Mouth: salivary amylase

Stomach: HCl, pepsin (protease)

Duodenum: pancreatic amylase, pancreatic lipase, trypsin (protease)

Small intestine: lactase, maltase (amylase), peptidase (protease)

What are the two types of gastric motility?

Peristalsis and Segmentation

How does peristalsis work?

Migrating contractions and subsequent relaxations will push bolus down the GI tract. CLEARING and propelling movement.

How does segmentation work?

Movement in alternate directions aids mechanical digestion through bolus colliding and churning in the small intestine. To move food, the rate of segmentation will change: higher near the stoamch, lower at end of SI

What is the function of saliva?

Important for taste, lubricating food, and adding amylase

How does food travel down the GI tract?

1. Mouth = mastication and salivary amylase

2. Esophagus = transport tube

3. Stomach = acidifies food, storage, protease, mechanical mixing, chemical digestion. Limited absorption due to ethanol

4. Small intestine = chemical digestion + absorption, bile salts for fat digestion from gallbladder

5. Large intestine = storage and void site, electrolyte + water reabsorption needed (enzyme cleaving raises osmolality, so it must uptake water to restore balance)

What are the phases of gastric regulation?

1. Basal: post absorptive phase

2. Cephalic: stomach gets triggered

3. Gastric: stomach gets more motility and secretions

4. Intestinal: decreased stomach activity to allow food processing in small intestine

What happens in the basal phase?

Activity of stomach in fasting

What happens in the cephalic phase? What glands are active?

Sensory from detecting food + swallowing will increase PNS activation to the medulla. This will tell the stomach to send a vagal output, which will prepare for food by secreting more acid + pepsin and increasing motility.

Salivary glands will be activated to lube and dissolve food so sugar can reach receptors in the mouth.

What happens in the gastric phase? What are the major hormones?

The presence of food (mainly protein) and swelling/distension in the stomach will trigger increased PNS, which will alert the medulla to trigger stomach motility and secretions. The stomach will secret gastrin, acid, and pepsin. This is a POSITIVE FEEDBACK LOOP, where turning one thing will turn on other things.

Gastrin is a hormone that will increase stomach secretions and motility.

What happens in the intestinal phase? What are the major hormones?

The entry of food and acid/gastric contents in the small intestines, increased osmolality from polymers breaking into monomers, and decreased pH will trigger an overall decrease in stomach activity that allows the SI to process food, which is aided by increase in hormone secretion.

Hormones secreted from the SI are CCK and secretin.

CCK will increase the number of digestive enzymes from the pancreas, secrete bile salts for fat digestion, and decrease stomach activity.

Secretin will increase bicarb from the pancreas to buffer the entering acid and decrease stomach activity. Secretin will also inhibit stomach emptying, acid, and pepsin secreiton.

How is the PNS involved in gastric regulation?

When it is triggered by stimuli in the cephalic and gastric phases, it gives the “go ahead” to increase stomach secretion and activity.

What secreting cells are found in the stomach?

G-cells, parietal cells, chief cells, mucous neck cells

What do G-cells do?

Also called enteroendocrine cells (entering endocrine). Will release gastrin into the blood, which activated chief and parietal cells

What do parietal cells do?

Releases HCl to acidify the stomach, whose low pH will kill bacteria and denature proteins

What do chief cells do?

Release pepsinogen. Upon contact with low pH, it will convet to its active form, pepsin

What do mucous neck cells do?

Release bicarbonate rich mucus to protect the stomach lining from HCl and pepsin

How is the pancreas stimulated?

CCK and Secretin, ANS

What are the exocrine and endocrine functions of the pancreas?

1. Exocrine = acinar cells that will

   1. produce bicarb to nautralize acidic chyme into SI

   2. enzymes from pancreas (protease, amylase, lipase, nuclease)

      1. protease will be secreted in inactive form, then be activated by brush border

2. Endocrine = islets of langerhans

   1. insulin and glucagon

What does endocrine insulin do?

Stimulate uptake of sugars and amino acids to decrease blood glucose. Also does conversion of glucose to fat

What does endocrine glucagon do?

Stimulates an increase in blood glucose from the liver through glycogenolysis (break down existing stores) and gluconeogenesis (create new)

What types of chemical digestion occurs in the small intestines?

1. Intraluminal = inside the lumen of the GI tract, and supplemented by enzymes released from pancreas

2. Membrane-associated = lcoated on epithelial of intestinal tract. Brush border enzymes will digest polymers to monomers

3. Intracellular = inside of the cell. Polymer → monomer

How does the gallbladder contribute to digestion?

The gallbladder is triggered by CCK from the pancreas, where it will secrete bile salts into the SI. Bile salts will emulsify fat and break down fat globules into micelles.

LIpase will digest TAG at the fat+bile salt+water interface.

How are sugars and proteins absorbed by the SI?

Amylase and protease. Because of their hydrophobic/lipophobic nature, they need help of facilitated diffusion and active transport to move across the membrane, or submucosa, where they enter circulation.

If they are small enough, they can transport themselves or be helped by ions.

How are fats digested by the SI?

Lipase will turn TAG into free fatty acids, which diffuses through the membrane with the help of chylomicrons. They will assemble FFA and transport it through lymphatic tissue, so it can enter circulation once again.

What are the phases of fasting?

1. Uses carbs. Shortest duration, hours to days.

2. Uses fats. Longest phase, weeks to months.

   1. Uses protein from essential organs and muscles. Medium phase, days to weeks. Death if too much catabolism

Stores are used in order, and will not be touched until the prior step is used.

What are the shortest and longest phases of fasting?

1 → 3 → 2

What occurs in Phase 1 of fasting in terms of changes in metabolism and mass loss?

Phase 1 will start at digestion and assimilation of nutrients to the body, and end when glycogen stores are used up.

Metabolic rate is depressed due to specific dynamic action, or the cost of digestion for processes beyond resting metabolism.

High daily mass loss as glycogen contains lots of H2O, making it a heavy fuel to burn.

What occurs in Phase 2 of fasting in terms of changes in metabolism and mass loss?

Phase 2 is dependent on fatty acid and the production of ketone bodies for metabolism.

Metabolic rate will continue to be depressed via thyroid hormones and daily activity.

What is the role of thyroid hormones during Phase 2 of fasting?

Adipocytes will store energy as fat and form adipose tissues.

1. Upon fasting, adipocytes will shrink due to less fat stores.

2. ↓ leptin secretion, which will normally tell hypothalamus that energy stores are fine. Upon less leptin, brain knows it is starvation time

3. ↓ leptin means ↓ thrytropin releasing hormone (TRH), which means ↓ pituitary thyroid stimulating hormone (TSH) secretion

4. ↓ TSH stimulation means ↓ thyroxine T3+T4 from the thyroid

5. ↓ T3+T4 means reduced mitochondria activity, making it more energy efficient by less heat loss and less O2 consumption.

What occurs in Phase 3 of fasting in terms of changes in metabolism and mass loss?

Fat is gone, switch to protein.

Metabolic rate is increased in the animal’s final effort to find food (increased activity)

More mass loss because protein is being burned, which has a lot of water weight.

What metabolic transition happens between meals?

Postprandial period, which occurs immediately after feeding. This includes nutrient absorption, utilization, and storage.

Hormones (insulin, glucagon, and cortisol) will control the level of nutrients needed.

Which hormones are involved in the postprandial period, and what do they do?

Glucagon (from alpha pancreatic) = increase blood glucose

Insulin (from beta pancreatic) = stimulate uptake of glucose

Cortisol (from adrenal cortex) = stimulates gluconeogenesis and mobilizes TAG from adipose tissue

What is the relationship between glucagon and insulin?

Glucagon is suppressed by insulin, which rises during the feed stage. Glucagon will rise during fasting.

What is the transition between feed to fasting stage?

Shift from nutrient storage to glucose maintenance and mobilization to tissues

Which hormones are catabolic, and which ones are anabolic?

Anabolic feeding phase: insulin

Catabolic fasting phase: glucagon, cortisol

What happens during hormonal regulation of metabolism?

During the anabolic fed stage, increases in insulin will stimulate glucose to make glycogen and fats, and amino acids to make protein, all for later usage.

During the catabolic fasting stage, glucagon and cortisol will increase.

• Glucagon will stimulate glycogen, glycerol alanine, and FFA to break down into glucose, glucose, and ketone bodies.

• Cortisol will stimulate fat, protein, and glyercol alanine to break down into fatty acids + glycerol + ketones.

Seals will fast during lactation. How does this affect them?

Elephant seals will lactate 55% body fat, so they are reliant on phase 2 and will reduce energy + water demands (breathing apnea, decrease SDA, reduce activity). They will cut off lactation before hitting phase 3

What is specific dynamic action?

Extra energy used beyond resting metabolism, but not movement energy. Essential functions (digestion)

What is hyperphagia?

Extreme, programmed need to eat. Animals will undergo this during seasonal changes, experiencing extreme body changes (like hibernation)

How does fasting affect the energy budgeting equation?

• Suspend repoduction (Pr)

• ↑ activity to search for food (Ma)

• ↓ energy stores (Ps), metabolism (Mbmr), body temp (Mt), SDA (Msda)

What happens to energy when converting between forms?

Chemical to mechanical forms will incur energy loss, as it is inefficient.

What is metabolic rate?

Amount of energy consumed per unit of time

What can metabolic rate tell us?

• Can quantitatively measure the “intensity of living,” or the physiological work of an animal

• Can determine food requirements

• Can determine how much energy must be consumed from the environment

How do you measure metabolic rate?

Indirect and direct calorimetry

What is direct calorimetry? How is it measured?

Directly measures rate of heat production for MR.

An animal is put into an ice chamber, and the rate of ice melted tells us heat from the animal.

Most accurate.

What is indirect calorimetry? How is it measured?

Indirectly measures heat production for MR, using O2 consumed and CO2 produced.

Uses respiratory quotient.

Less accurate, as you need to know what fuel is burned.

Which is more accurate, indirect or direct calorimetry?

Direct, because for indirect you need to know what fuel is being burned.

What is the respiratory quotient?

(mL of CO2 produced)/(mL of O2 consumed)

Can indicate the oxidized fuel an animal uses. Measured under aerobic conditions.

What number is used for the base RQ?

0.8 is used when calculating heat production. We are 0.8 at rest.

What are the RQ metabolic signatures for each fuel source, and what principle is it based off?

Based on the principle that fuels will require a different amount of O2 to be burned, associated with burning 1g.

Fat = 0.7

Protein = 0.8

Carbohydrates = 1.0

What is the difference between respiratory quotient (RQ) and respiratory exchange ratio (RER)?

RQ: Tissue used

RER: Respiratory exchange of CO2 and O2

In hummingbird flight metabolism, how will the respiratory quotient change between rest and flight? Which metabolism is used?

Rest

• Low intensity activity

• Aerobic metabolism

• RQ = 0.7, fat is burned

Flight

• High intensity activity

• Anaerobic metabolism due to glycogen use

• RQ = 1.0, carbs are burned

What is basal metabolic rate (BMR), and which animal uses it?

Endotherm. The lowest energy used for existence, where the animal is in…

• thermal neutral zone (no thermoregulation)

• at rest (inactive)

• post absorptive (after digestion, no intake)

• free of physical and psychological stress

What is standard metabolic rate (SMR), and which animal uses it?

Ectotherm. Lowest energy used for existence. Same conditions as BMR, but you must standardize the temp to stabilize core body temperature. (Q10 principles)

What is field metabolic rate (FMR)?

MR of normal activity. Restriction is peak activity.

What is maximum metabolic rate (MMR)?

AKA Vo2 max. MR of peak activity, no restrictions

What defines an endotherm?

Super energy!

• Expensive, high BMR will raise Tb above Ta

• Narrow range of body temperatures, as you must adjust your body Tb

• High MMR

• High water loss

What defines an ectotherm?

Low energy…

• Cheap, low SMR will not raise Tb over Ta

• Wide range of body temps

• Low MMR

• Low water loss

• Unique body shapes, as SA/V ratio not important

Which type of animal is more likely to have a unique body shape, and why?

Ectotherm, as surface area to volume ratio is not as important as endotherms

How is ectothermy and endothermy defined?

Metabolic rate and whether metabolism can raise Tb above Ta

What does energy flow take into consideration?

GE = NE + FU

• GE = ingestion of food

• NE = absorbed chemical energy, internal/external maintenance + production

• FU = unabsorbed and unmetabolizable energy

How is absorption efficiency measured?

Ratio of absorbed energy to ingested energy

What is the energy budgeting equation?

GE = (Mbs + Md + Ma + Mt) + (Pg + Pr + Ps) + (F + U)

• b/s = basal/standard MR

• d = SDA

• a = activity

• t = thermal work

• g = somatic growth

• r = reproductive growth

• s = storage

• f = feces

• u = urine

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How do animals allocate resources to different physiological processes through life?

It will shift through life, and is not fixed.

• ex. in early stages of rapid growth, Ps will dominate net energy gained. later life will Pr

What is net growth efficiency?

How efficiently an animal will convert ingested energy into selfish growth

What is scaling?

The relatinoship between body size, mass, and a parameter (MR, organ size, etc)

What is the scaling equation?

A general relationship between body mass + parameter.

• Y=a(X)^b

  • Y=MR

  • X=BM

  • b=proportional change in X and Y

  • a=y-intercept

  • b= slope

What is an isometric scaling relationship?

• How is it represented numerically?

• What is an example of it?

Proportional change. b=1. Anatomy, structures, organs

What is an allometric scaling relationship?

• How is it represented numerically?

• What is an example of it?

Nonproportional change. b NOT 1. Physiology (MR, HR, respiratory)

What is Max Rubner’s Surface Law?

Believed heat loss is determined by SA/V, in which small animals have more SA/V. This means they must generate more heat to maintain Tb, and b=0.67 for all animals.

This predicted that heat loss must be replaced.

Y=m(mass)^0.67

Why was Rubner disproven?

It is only true within a single species, and will not apply across species. The same rule will apply to ectotherms and endotherms, as long as you are kept within those animals.

What is Kleiber’s ¾ Power Law?

Proved by WAMR. b when making comparisons across species is around 0.75.

Y=a(mass)^0.75

Which law and number best describes letter b in the scaling equation?

Kleiber’s ¾ Power Law; b=0.75

What does whole animal metabolic rate mean?

MR increases as the animal gains mass, but overall mass increases faster than WAMR

• Allometric

• Also known as skrew to elephant plot

• Y=a(X)^0.75

What does mass-specific metabolic rate mean?

As mass increases, MSMR decreases. Metabolism of 1g of tissue.

• Allometric

• Y=a(x)^(-0.25)

Why allometric? Can it explain the MR of all animals?

• Ectotherms will be allo, even though Tb will change with TA. This means it is not about maintaining a constant body temp.

• Endo has x4-10 higher resting MR

  • ex. humans at 98F will have a fast MR due to higher temp for rxn

Which theory explains allometricity, multiple cause theory or fractal theory?

Multiple cause theory; metabolism is explained by multiple processes.

1. Smaller animals tend to have more mitochondria per cell; negative relationship between mitochndria and size

2. Differences in futile sizes (variation of magnitude fo leak/pump cycles like ion leaks and ATP pumps); small animals can have larger cycles = higher MR

How does activity affect metabolism?

Total activity will determine the energy used for the day

Habitat quality will affect the needed energy to get food, so low quality habitats mean increased daily MR

What is the relationship of SDA to size of meals?

SDA will increase with food consumption; more work must be done to compensate for a big meal

What are the key temperatures across an animal’s body?

Internal to External

1. Body core (Tb)

2. Peripheral temp (Tp)

3. Surface temp (Ts)

4. Environment temp (Ta)

Heat transfer will occur between animals and the environment.

What is the thermal budgeting equation

Balance of heat loss and gain

Total = M + CD + CV + R + E

• M = metabolism, gain via chem, mech, elec processes

• CD = conduction, gain/loss thru direct contact of body + environment

• CV = convection, gain/loss thru movement of air/H2O around body

• R = radiation, gain/loss. ex, clouds will cover the sun and make things cold

• E = evaporation, loss thru latent heat of evaporation

What is a poikilotherm?

Will confirm body temp to environ