Biology 272a: Comparative Animal Physiology

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Biology 272a Comparative Animal Physiology

• Diving mammals

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Dive record of a male northern elephant seal
Fig. 25.4
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Dive durations of Weddell seals
Fig. 25.1a
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Problems with diving

• Oxygen
• Nitrogen
• Waste products
• CO2
• Lactate

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Forced diving

• Led to an extreme diving response
• The seal didnt know how long it would be
  underwater!

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Natural Diving
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Natural diving
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The classical diving response

• Apnoea
• Bradycardia
• Vasoconstriction and reduced blood flow

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Oxygen

• or lack thereof

Blood lactate
Aerobic dive limit
Fig 25.12
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Oxygen stores
Fig. 25.6
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Conserving oxygen

• Peripheral vasoconstriction
• Hypoperfusion of viceral organs
• Brain retina remain normoxic

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Body and heart-lung-brain become separate
compartments
Blood O2 remains high
Muscle O2 depleted
Fig. 25.10a
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Harbor seal breathing air
2 s
6 s
0.5 s
Fully perfused kidney and other viceral organs
Fig. 25.7 a-c
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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
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Waste products CO2

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

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Waste products - lactate
Anaerobic metabolism is compartmentalised
Fig. 25.10b
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Waste products - lactate
Fig. 25.11
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The Bends

• Workers in pressurised mine shafts and tunneling
  projects in 19th C
• Caisson disease
• PN2 (lungs) gt 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

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Why dont 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
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Compressed alveoli an oxygen supply for
resurfacing?
Decreasing depth and pressure
More O2 becomes available during ascent
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Gradations of the diving response
Fig. 25.1
Fig. 25.2
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Gradations of the diving response
Fig. 25. 9
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The classical diving response

• Apnoea
• Bradycardia
• Vasoconstriction and reduced blood flow

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Thats it!

• See you Thursday for the review session
• Fun (ie non-examinable) lecture about my
  research next Tuesday.