Diving Physiology Flashcards
Humans with diving adaptations
Ama divers in Japan (reduced expiration flow), Pearl divers of the Tuamoto Archipelago and Extreme divers.
Adverse effects of diving in humans
The bends, oxygen toxicity, narcotic effect of gases, oxygen supply and effects of high pressure.
The Bends
Occurs when humans return to surface after prolonged time at depth of 20+ meters, with higher severity in greater depths and time.
What causes the bends?
Bubbles of nitrogen forming in the blood.
Symptoms of the bends
Joint and muscle pain, neurological problems, headaches and strokes.
Boyle’s Law
Volume of a sample of gas is inversely proportional to the pressure applied to the gas if temperature is constant
What happens every 10m of depth?
Subjected to 1 extra atmosphere of pressure.
ppO2 at sea level
0.2 atm.
ppO2 at 10m (2 atm)
0.4 atm.
ppO2 at 40m (5 atm)
1.0 atm.
What does higher pressure at depth cause?
More nitrogen dissolves in blood/
How can the bends be avoided?
Rapid descent and a short time at depth, to prevent bubble formation diver must ascend carefully with stops at various depths with a quick initial ascent to half depth and then slower after.
Why must you exhale?
To prevent lung rupture.
How are the bends overcome?
Staying still as bubble formation is increased by muscle movement, can only be treated by increasing pressure so bubbles redissolve.
How can the diver increase pressure?
Back down to the depths or enter a decompression chamber.
Can helium be used for diving?
It is safer than nitrogen and less likely to form bubbles but it is expensive with evidence of helium narcosis.
Heliox
Used below 30 metres to 200-250m, has around 10% oxygen.
What happens at 150m?
High pressure nervous syndrome or the shakes with dizziness, nausea and drowsiness.
Trimix
Used below 250m, uses oxygen, helium and nitrogen up to 450m depth.
Pure oxygen at 1atm
Harmful for most animals, after 24 hours distress and increased lung irritation with rats dying after a few days due to irritation.
Pure oxygen at 2atm
Nervous symptoms develop before lung irritation, causes convulsions and movement reduces tolerance.
Pure oxygen at 3atm
Tolerated for a few hours.
Pure oxygen at 7atm
Convulsions after 5 minutes.
Problems with oxygen for diving
Seizures and coma, nausea and disorientation, pulmonary oedema and issues with reactive oxygen species
Nitrogen at 36 metres for 1 hour
Nitrogen narcosis.
Nitrogen at 45-60 metres for 1 hour
Drowsiness.
Nitrogen at 75+ metres for 1 hour
Akin to alcohol overexposure, the raptures of the depths.
Nitrogen at 90 metres for 1 hour
Unconsciousness and death.
Safe limit for compressed air
30 metres, can become 50 metres with repeated exposure.
Methods to manage oxygen supply in diving air-breathing animals
Increase oxygen storage, decrease oxygen consumption, use of anaerobic processes and aquatic respiration.
How do animals increase oxygen storage?
Larger blood volume, higher haemoglobin content in blood and higher myoglobin content in muscle.
How do animals decrease oxygen consumption?
Decrease metabolism and heart rate.
How do animals use anaerobic processes?
Switch to lactic acid formation.
How do animals use aquatic respiration?
Cutaneous (frog and sea snakes) and oesophageal or rectal respiration (some turtles).
What triggers diving reflex in humans?
Chemoreceptors on face and nostrils activated by contact with cold water, carried along 5th cranial nerve to the brain.
Diving reflex
Stop breathing, reduce heart rate, peripheral vasoconstriction and splenic contraction.
Cardiovascular changes in diving
Peripheral resistance increases as a result of a change in the blood vessels caused by catecholamines of the SNS and bradycardia also occurs.
Metabolic rate change when diving in seals
If no change occurred, seal would use up oxygen in five minutes versus the average 20 minute dive.
Lactic acid formation
Most muscles receive no blood in a dive, so work based on anaerobic processes causing lactic acid formation and accumulation in the muscle, this is immediately shifted to blood after a dive and is gradually removed.
How is lactic acid removed?
Synthesised into glycogen by liver and muscles or into carbon dioxide and wate
Origin of diving reflex
Found in all air-breathing vertebrates, associated with transition to air-breathing at birth and has a similar response to fish out of water.
Effects of high pressure
Increase in pressure causes dissociation of weak acids and bases, changes in protein structure, contractile effects of muscles and impacts gases.
Longest underwater dive
11:54.
Static apnea depth record
214m.
Two types of changes to adapt to environments
Purely physiological or genetic.
Link of mammals/birds and aquatic species
Most mammalian orders and birds have an aquatic representative such as monotrema have the aquatic platypus and ostriches have the penguin.
Depths dived by whales, seals and turtle
Sperm whale can dive 2,000m, Southern elephant seal can dive 1,620m and Leatherback turtle can dive 1,280m.
Weddell seals diving behaviour
Dive for 10-20 minutes
Elephant seals diving behaviour
Dive for 30-40 minutes but up to 120 mins.
Emperor penguins diving behaviour
Dive for up to 22 minutes.
Whales diving behaviour
Can dive up to 2 hours.
Animals evolutionary adaptations to aid diving
Increase oxygen levels, decrease oxygen requirements and evolve countermeasures for other issues.
How do diving animals increase oxygen availability?
Increased muscle myoglobin (up to 60% of O2 in muscle), increase haematocrit by 10-20% and increase spleen volumes which act as red blood cell reservoirs.
What is haematocrit a measure of?
Percentage of blood sample that is RBC.
Human oxygen stores
45% respiratory, 40% blood and 15% muscle.
Sperm whale oxygen stores
7% respiratory, 60% blood and 33% muscle.
Weddell seal oxygen stores
5% respiratory, 65% blood and 30% muscle.
How do animals lower oxygen requirements?
Bradycardia, peripheral vasoconstriction, reduced hepatic and renal perfusion, colder temperature can reduce circulation and cost-efficient locomotor activity.
Weddell seal gliding
Gliding dives are much more oxygen efficient than stroking dives.
How have animals evolved countermeasures to the bends?
Whales and seals breathe out before diving and store only 7% oxygen in their lungs, with lung collapse at depth and less perfusion prevents nitrogen and oxygen transfer while at the depths.
How do diving animals prevent nitrogen narcosis?
They have reduced lung volumes with a modified bronchiolar structure that is more muscular allowing for closing of air passages.
How can animals reduce sensitivity to pCO2?
Holding breath causes a rise in CO2 levels causing increase in blood pH, so evolved blood with high buffering capacity.
Oxygen-Hb dissociation curve in penguins vs ducks
Shifted to the left in penguins so haemoglobin is saturated at higher pO2 and stripped at lower pO2 allowing for oxygenation in hypoxic environments.
