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Gas Exchange

Gas Exchange. air > alveoli > blood > hemoglobin in RBC > muscle tissue normal conditions - oxidative metabolism supplies body, matches rate of need increased exercise shows linear increase in O 2 uptake to a point, then plateaus with increased speed VO 2 max . VO 2 max.

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Gas Exchange

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  1. GasExchange • air > alveoli > blood > hemoglobin in RBC > muscle tissue • normal conditions - oxidative metabolism supplies body, matches rate of need • increased exercise shows linear increase in O2 uptake to a point, then plateaus with increased speed • VO2max

  2. VO2max • maximal amount of oxygen used by the athlete during maximal exercise to exhaustion • determined by increasing workload or speed of treadmill in a stepwise manner • Humans 69-85 ml O2/kg/min • Thoroughbreds 160 ml O2/kg/min • Greyhounds 100 ml O2/kg/min • Camel 51 ml O2/kg/min

  3. VO2 max • can be used as an assessment of fitness (ability for aerobic energy transfer) • VO2 max reached at heart rate of approx. 200 bpm • horses have higher VO2max per kg BW • increased heart size • increased hemoglobin concentration • increased peripheral capillary bed • large skeletal muscle mass has higher density of mitochondria (aerobic metabolism) • spleen > increased RBC > increased hemoglobin > increased affinity of O2 and enhances O2 diffusion

  4. Carbon Dioxide Transport • dissolved CO2 in plasma • 5% • carbamino compounds - combined with and amino group • 15-20% • combined reversibly with H2O • 60-80% • CO2 + H2O  H2CO3 H+ + HCO3- • with excessive exercise (100% VO2 max), some CO2 not eliminated; unique to horse

  5. Oxygen Transportation • small amount dissolved in blood (< 2%) • combined with hemoglobin (98 %) • 4 O2 molecules per hemoglobin (oxyhemoglobin) • Hemoglobin • each gram of oxygen-saturated hemoglobin binds 1.34 ml O2 • 15 g Hg = 20.1 ml/100 ml blood • 20 g Hg = 26.8 ml/100 ml blood • anemia - decreased hemoglobin - O2 content decreased • oxygen dissociation curve

  6. Hemoglobin Dissociation Curve • Bohr effect (triggered by H+ in blood) • right shift of curve due to decreased pH of blood (acidic) • hemoglobin unloads O2 more readily to muscle • higher pH in lung, hemoglobin loads up on O2 • muscle pH decreases with exercise • increases in arterial PCO2 in blood unloads more O2 • temperature • right shift with increases blood temperature • hemoglobin unloads more O2 in heated active muscle • not much effect at low intensity work level

  7. Locomotor-Respiratory Coupling • effect of natural anatomical driving forces • walk - no effect • trot and pace • ratio 1:, 1:3 or 2:3 • canter and gallop • 1:1 • compression of chest from driving force of weight on front limbs • pressure of diaphragm • visceral piston (30% of BW) • change in axis of body

  8. Response to Exercise • respiration rate and tidal volume increase to bodies need • regulated by chemoreceptors in response to O2, CO2 and pH of arteries • locomotion mechanics override chemoreceptors at canter and gallop

  9. Recovery Following Exercise • affected by work intensity, fitness and climate • rapid decrease in rate, repay “ O2 debt ” • deep breaths to 60-100 bpm • re-synthesis of phosphocreatine in exercised muscle • catabolism and anabolism of blood lactate • restore hormonal reserves • lower body temperature • regulated by airway and skin temperature • analysis - rate & depth, HR, rectal temperature, and physical state

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