Chapter 26 Outline
Diving Feats and Behavior
Types of Dives and the Importance of Method
Physiology: The Big Picture
The Oxygen Stores of Divers
- The blood O2 store tends to be large in diving mammals
- Diving mammals have high myoglobin concentrations and large myoglobin-bound O2 stores
- Diving mammals vary in their use of the lungs as an O2 store
- Total O2 stores never permit dives of maximum duration to be fully aerobic
Circulatory Adjustments during Dives
- Regional vasoconstriction: Much of a diving mammal’s body is cut off from blood flow during forced or protracted dives
- Diving bradycardia matches cardiac output to the circulatory task
- Cardiovascular responses are graded in freely diving animals
- Red blood cells are removed from the blood between dive sequences in some seals
- BOX 26.1 The Evolution of Vertebrate Cardiac and Vascular Responses to Asphyxia
Metabolism during Dives
- The body becomes metabolically subdivided during forced or protracted dives
- Metabolic limits on dive duration are determined by O2 supplies, by rates of metabolic O2 use and lactic acid production, and by tissue tolerances
The Aerobic Dive Limit: One of Physiology’s Key Benchmarks for Understanding Diving Behavior
- Marine mammals exploit multiple means of reducing their metabolic costs while underwater
Decompression Sickness
- Human decompression sickness is usually caused by N2 absorption from a compressed-air source
- Breath-hold dives must be repeated many times to cause decompression sickness in humans
- Marine mammals have been thought—perhaps erroneously—to avoid decompression sickness during deep dives by alveolar collapse
- Decompression sickness is an unresolved phenomenon