Chapter 26 Diving by Marine Mammals

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  1. Fig 26.2 Durations of dives by wild Weddell seals
  2. Fig 26.3 Depths of dives by wild Weddell seals
    1. up to 600 m
    2. Other Depths:
      1. Penguins - 500 m
      2. Sperm Whales - 1000 m
      3. Elephant Seals - 1500 m
    3. Duration
    4.  of dives
      1. Most diving ~ <20 min
      2. Weddell Seals: up to 2 hrs
  3. Oxygen Supply During Diving in Elephant seals
    1. Figure 26.5: Diving by an individual elephant seal (Moo)
    2. can dive for up to 120 minutes
    3. Can spend 40 days underwater with surface intervals 6 minutes or less
  4. Diving Physiology: Challenges of Diving
    1. Skeletal muscles, Brain, Heart
    2. require most energy
    3. Brain and Heart
    4. need the most O
    5. Hypoxia:
    6. cannot breathe while under water
  5. Blood O2 stores in diving mammals
    1. Carrying capacity: amount of O2 per volume
    2. Weddell seals have twice the normal value
    3. Blood volume: Sperm whales have twice the normal volume ratio  
  6. Blood O2 stores in diving mammals
    1. high blood O2 concentrations,
      1. Carrying capacity
      2. Blood volume:
    2. Total Blood O2 stores = Carrying capacity X Volume.  
  7. Muscle O2 stores in diving animals
    1. much higher muscle myoglobin content than in terrestrial mammals.
    2. higher affinity of myoglobin for oxygen
  8. Lung O2 stores in diving animals
    1. Lung air creates buoyancy, which makes diving difficult
    2. Diving mammal lungs are compressible
  9. Figure 26.7 A comparison of the total O2 stores of five species of marine mammals and humans
    1. deep diving mammals have small lungs
    2. deep diving seals have twice as much blood with about twice the carrying capacity
    3.  High myoglobin (about 10 times human muscle)
  10. Diving Physiology: Challenges of Diving
    1. Brain and heart tissue run almost entirely on aerobic metabolism
    2. skeletal muscles can utilize anaerobic metabolism
  11. Diving response,1 Collapse of the lung: (Fig. 26.6)
    1. Deep divers exhale before diving;
    2.  Alveolar collapse pushes N2 away from the blood, (Fig. 26.16)
  12. Diving Response, 2 Bradycardia
  13. Figure 26.10 Diving heart rate varies with dive duration in a graded manner in freely diving seals
  14. Cardiac and Vascular Responses to Asphyxia
    1. in reptiles, the heart almost stops
    2. some fish do this when in air  (Box 26.1 The heart rates of fish removed from water)
  15. Diving Response, 3 Peripheral vasoconstriction
    1. 1.Major feature of the diving response.
    2. Reduced blood flow to every tissue except brain and heart.
  16. Figure 26.9 Circulatory patterns are radically changed during forced or prolonged submergence
    1. Shunting:  blood is kept from all but vital organs (brain gets most)
    2. lactic acid builds up in muscle
  17. Figure 26.10 The forcibly submerged seal as a 'heart-lung-brain machine'
  18. Oxygen Supply During Diving
    1. Decreased metabolic rate
    2. Increased anaerobic metabolism
    3. Oxygen debt must be repaid after diving
  19. Figure 26.12 Metabolic subdivision of the body in seals during forced submergence
  20. Figure 26.13 The aftermath of a prolonged dive: Lactic acid in muscles and blood
  21. Diving Response
  22. Aerobic Dive Limits: What limits dive duration?
  23. Aerobic Dive Limits
  24. Diving Response, 4
    1. 1.Increase in hematocrit (in a few cases): Weddell seals store RBCs in their spleen.
  25. oxygen supply during diving
    1. cutaneous and rectal respiration
  26. Decompression sickness (the bends)
    1. Human diver at depth breathes air at high pressure
  27. The Bends
  28. How marine mammals avoid the bends
    1. sperm whales can dive to over 1100 m
    2. elephant seals can dive to over 1500 m  
    3. avoid bends by not super-saturating blood
  29. Problem 2: Oxygen Toxicity
  30. Problem 3: Narcotic Effects Of Inert Gases
    1. Nitrogen at several atmospheres causes intoxication like laughing gas (rapture of the deep)


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