Lecture notes from Biol2018 adaptive physiology Diving and High altitude physiology. Covering: adverse effcts of diving, the bends, oxygen toxicity, metabolic rates, effects of high pressure, increasing oxygen availability - high altitude, altitude sickness, haemoglobin and oxygen affinity
Diving and High-Altitude
Physiology
Diving
Adverse effects of diving in humans
The bends
Oxygen toxicity
Narcotic effects of gases
Oxygen supply
Effects of high pressure
The bends
Dangerous syndrome when human divers return to surface after prolonged time at
depths below 20m
More severe with greater depths and dive time
Caused by bubbles of nitrogen forming in blood
Symptoms include joint and muscle pain and neurological problems, headaches, and
strokes
Boyle’s law – the volume of a sample of gas is inversely proportional to the pressure
applied to the gas if the temperature is kept constant – higher pressure at depth so
more N2 dissolves in blood/fat
Avoidance – ascending in stage with stops at various depths
Treatment – re-descend so bubbles redissolve or enter a compression chamber
Oxygen toxicity
Pure O2 at 1 atm – harmful for most animals – lung irritation
2 atm – nervous system issues develop before lung irritation – convulsions
3 atm – only tolerated for a few hours
7atm – convulsions after 5 mins
Main problems: seizures and coma, nausea and disorientation, pulmonary oedema
etc.
Gases for diving – air then helium and then nitrogen
Managing Oxygen supply in diving air-breathing
animals
Increased oxygen storage – larger blood volume and higher haemoglobin content –
higher myoglobin content in muscle
Decreased oxygen consumption – decreased metabolic and heart rate
Use of anaerobic processes – lactic acid formation
Aquatic respiration – cutaneous respiration (frog and sea snakes)
Oesophageal or rectal respiration (some turtles)
Diving Reflex
Chemoreceptors on the face and nostrils activated by contact with cold water
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