4' Factors influencing carrying capacity

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• 4. Factors influencing carrying capacity
• More Hb carries more O2
• Achieved by more rbcs
• Hematocrit
• percentage of blood that is rbcs
• usually 20-50 (poiks 20-35 homeos 30-50)
• Increased hematocrit increases blood viscosity
• RBC production stimulated by hormone
  erythropoietin
• released from kidney by low pO2 in blood

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F. Oxygen transport from blood to cells
ECF
O2 must leave Hb diffuses to cells via ECF
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• ECF contains additional pigment to facilitate
  diffusion
• Myoglobin
• 1/4 hemoglobin
• much higher affinity

Mg function 1. facilitates O2 diffusion in
ECF 2. stores O2 in ECF in cells with high
demand
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• G. Specialized Respiratory Problems
• 1. Diving
• Problems
• no O2 source, no CO2 removal
• increased pressure drives inert gases into blood

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• Solutions
• a. Keep gas out of lungs exhale
• b. Store O2 in body
• increase blood volume, red blood cells
• increase myoglobin
• c. Decrease O2 demand
• diving reflex decrease cardiac output
• d. Tolerate high anaerobic activity
• keep lactate in muscles

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• 2. High Altitude
• Problems
• decreased pO2, 50 for every 5500 meters
• Solutions
• a. Increase ventilation
• b. Increase carrying capacity red blood cells
• c. Increase cardiac output, lung function
• d. Decrease activity

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• X. Osmoregulation
• A. Physical Principles of Salt and Water
• 1. Compartmentalization
• Vertebrates are 65-80 water
• 75 intracellular
• 20 extracellular
• 5-10 vascular
• All contain solutes

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• 2. Dissolved solute in water creates osmotic
  pressure
• Higher solute, higher pOs
• a. Osmolarity
• moles of dissolved particles/liter
• b. Osmolarity determines pOs
• and therefore water movement between compartments

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• 1 mole of sucrose in 1 liter
• 1 osmolar sucrose
• 1 osmole/L
• 1000 mosm/L
• 1 mole of NaCl in 1 liter
• 2 osmolar for Na and Cl-
• 1 M solution of NaCl has higher pOs than 1 M
  sucrose

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• 1 M NaCl hyperosmotic to 1 M sucrose
• 1 M sucrose hypoosmotic to 1 M NaCl
• 0.5 NaCl isoosmotic to 1 M sucrose
• WATER moves by osmosis from hypoosmotic to
  hyperosmotic solution

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• Animals work to maintain most compartments
  isoosmotic
• Achieved at the cellular level by channels and
  pumps
• Achieved at the organismal level by
  Osmoregulatory Organs
• control animals salt and water content

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• 3. Osmoregulatory Environments
• a. Aquatic
• (1) Sea water 1000 mosm/L
• (2) Freshwater lt100 mosm/L
• b. Terrestrial
• (3) Mesic moist, plenty of fresh water
• (4) Xeric dry, restricted fresh water

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• 4. Most vertebrates regulate body fluids and
  blood at 300-350 mosm/L
• a. Sea water
• animal hypoosmotic to medium
• lose water by osmosis dehydration
• gain salt by diffusion
• b. Freshwater
• animal hyperosmotic to medium
• gain water by osmosis hydration
• lose salt by diffusion

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• c. Terrestrial
• wet animal in dryer air dehydration
• take up and keep water, especially in xeric

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• B. Osmoregulatory Organs
• regulate composition of internal environment
• 1. Kidney
• a. General Functions
• (1) control water content of blood
• (2) control ratio and concentration of blood
  salts
• (3) eliminate wastes from blood

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• b. Basic functional unit is nephron
• Two compartments
• (1) Filtrate fluid contained in kidney tubule
• (2) Blood fluid contained in capillaries
• Basis for function is exchange between these two
  compartments

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• c. Exchange mechanisms
• (1) Glomerular Filtration
• movement of water and all except biggest solutes
  from blood in capillaries
• to filtrate in kidney tubule
• Based on Starling Hypothesis
• pHy elevated over pOs so fluid leaves blood

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• (2) Tubular Reabsorption
• selective reuptake of desirable substances
• e.g., water nutrients, salts
• from filtrate in tubule back to blood in caps

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• (3) Tubular Secretion
• selective pumping of additional wastes from
  blood to filtrate
• Final Filtrate
• salts, wastes, and water excreted from animal as
  urine

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• d. Structure
• (1) Kidney tubule
• (2) Collecting duct
• to ureter and bladder

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• (3) Circulation
• (4) All nephrons in parallel

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• e. Kidney Function
• (1) Glomerulus filtration
• Net effect
• large volume of H2O and all solutes less than
  approx. 25,000 MW move to filtrate
• large proteins stay behind in blood to
  efferent arteriole

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• (2) PCT tubular reabsorption
• selectively recover desirable substances to
  blood
• e.g., 75 of Na actively pumped back
• also K, HCO3-, Cl-
• glucose, amino acids actively reabsorbed

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• When salts pumped across membrane, water follows
  passively by osmosis
• osmotic drag
• water is therefore drawn back into blood
• Net Effect at PCT
• water, salts, nutrients recovered to blood
• filtrate becomes isoosmotic to blood

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• (3) Loop of Henle
• (a) descending loop
• impermeable to salts leaving
• highly permeable to water
• As filtrate descends,
• water leaves to hyperosmotic ECF
• salt remains
• Therefore filtrate concentrates

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• (b) ascending loop
• impermeable to water
• actively pumps out NaCl
• As filtrate ascends,
• salt leaves and water is retained
• Therefore filtrate dilutes
• Salt is being recycled from the ascending to
  descending loops through the ECF
• Constant recycling of salt creates
• standing salt gradient in kidney medulla