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Biology 272a: Comparative Animal Physiology

Biology 272a: Comparative Animal Physiology. Diving mammals. Dive record of a male northern elephant seal. Fig. 25.4. Dive durations of Weddell seals. Fig. 25.1a. Problems with diving. Oxygen Nitrogen Waste products CO 2 Lactate. Forced diving. Led to an extreme diving response

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Biology 272a: Comparative Animal Physiology

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  1. Biology 272a: Comparative Animal Physiology Diving mammals

  2. Dive record of a male northern elephant seal Fig. 25.4

  3. Dive durations of Weddell seals Fig. 25.1a

  4. Problems with diving • Oxygen • Nitrogen • Waste products • CO2 • Lactate

  5. Forced diving • Led to an extreme diving response • The seal didn’t know how long it would be underwater!

  6. “Natural” Diving

  7. Natural diving

  8. The classical diving response • Apnoea • Bradycardia • Vasoconstriction and reduced blood flow

  9. Oxygen • …or lack thereof Blood lactate Aerobic dive limit Fig 25.12

  10. Oxygen stores Fig. 25.6

  11. Conserving oxygen • Peripheral vasoconstriction • Hypoperfusion of viceral organs • Brain & retina remain normoxic

  12. Body and heart-lung-brain become separate compartments Blood O2 remains high Muscle O2 depleted Fig. 25.10a

  13. Harbor seal breathing air 2 s 6 s 0.5 s Fully perfused kidney and other viceral organs Fig. 25.7 a-c

  14. Harbor seal in forced dive 2 s 6 s 0.5 s Breathing Air No perfusion of kidney and other viceral organs Fig. 25.7 d-e

  15. Waste products – CO2 • High blood buffering capacity • Reduced changes in blood pH • Reduced ventilatory response to CO2 • Or increased threshold • Post-dive hyperventilation

  16. Waste products - lactate Anaerobic metabolism is compartmentalised Fig. 25.10b

  17. Waste products - lactate Fig. 25.11

  18. “The Bends” • Workers in pressurised mine shafts and tunneling projects in 19th C • Caisson disease • PN2 (lungs) > PN2 (blood & tissue) • results in increased N2 in tissues and fluids • Rapid decompression results in N2 coming out of solution • Bubbles of N2 gas in joints cause “the bends” • Other symptoms also due to bubbles and/or high [N2]

  19. Why don’t seals get the bends? Air is compressed out of gas exchange surfaces, so N2 cant diffuse into bloodstream … but nor can O2… Fig. 25.5 Compressible thorax Fig. 24.14

  20. Compressed alveoli… an oxygen supply for resurfacing? Decreasing depth and pressure More O2 becomes available during ascent

  21. Gradations of the diving response Fig. 25.2 Fig. 25.1

  22. Gradations of the diving response Fig. 25. 9

  23. The classical diving response • Apnoea • Bradycardia • Vasoconstriction and reduced blood flow

  24. That’s it! See you Thursday for the review session “Fun” (ie: non-examinable) lecture about my research next Tuesday.

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