Lecture notes BIOL2018 Diving and High altitude physiology

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