Title: Biology 272a: Comparative Animal Physiology
1Biology 272a Comparative Animal Physiology
2Dive record of a male northern elephant seal
Fig. 25.4
3Dive durations of Weddell seals
Fig. 25.1a
4Problems with diving
- Oxygen
- Nitrogen
- Waste products
- CO2
- Lactate
5Forced diving
- Led to an extreme diving response
- The seal didnt know how long it would be
underwater!
6Natural Diving
7Natural diving
8The classical diving response
- Apnoea
- Bradycardia
- Vasoconstriction and reduced blood flow
9Oxygen
Blood lactate
Aerobic dive limit
Fig 25.12
10Oxygen stores
Fig. 25.6
11Conserving oxygen
- Peripheral vasoconstriction
- Hypoperfusion of viceral organs
- Brain retina remain normoxic
12Body and heart-lung-brain become separate
compartments
Blood O2 remains high
Muscle O2 depleted
Fig. 25.10a
13Harbor seal breathing air
2 s
6 s
0.5 s
Fully perfused kidney and other viceral organs
Fig. 25.7 a-c
14Harbor 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
15Waste products CO2
- High blood buffering capacity
- Reduced changes in blood pH
- Reduced ventilatory response to CO2
- Or increased threshold
- Post-dive hyperventilation
16Waste products - lactate
Anaerobic metabolism is compartmentalised
Fig. 25.10b
17Waste products - lactate
Fig. 25.11
18The 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
19Why 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
20Compressed alveoli an oxygen supply for
resurfacing?
Decreasing depth and pressure
More O2 becomes available during ascent
21Gradations of the diving response
Fig. 25.1
Fig. 25.2
22Gradations of the diving response
Fig. 25. 9
23The classical diving response
- Apnoea
- Bradycardia
- Vasoconstriction and reduced blood flow
24Thats it!
- See you Thursday for the review session
- Fun (ie non-examinable) lecture about my
research next Tuesday.