Diving Physiology Flashcards
Hypoxia
Decline of available O2
Hypercapnia
Increase in CO2
Asyphxia
Hypoxia + Hypercapnia = High CO2
Acidosis
Accumulation of lactic acid
Ischemia
Tissues deprived of circulating blood
What are the two main challenges that diving marine mammals face?
- Hydrostatic pressure
- Oxygen conservation
What is Boyle’s Law?
- Pressure and Volume are inversely proportional
- Pressure increases by 1 atm every 10m
As volume increases, pressure decreases
What is Henry’s Law?
The amount of dissolved gas in a liquid is proportional to the partial pressure above the liquid
As pressure increases, solubility increases
How does Henry’s Law pose a problem for deep diving marine mammals?
The bends
Describe the Bends (related to Henry’s Law)
- As dive depth increases, pressure increases, gas solubility increases (N2)
- On ascension dissolved gasses come out of solution in the form of bubbles inside the body
- This can cause many symptoms depending on where bubbles form and where bubbles migrate
What are some reasons why marine mammals don’t get the bends?
- Isolate N2 from the site of gas exchange (move air into upper airway where it is not in contact with blood)
- Collapse lung (no gas exchange)
- Exhale before diving (air in lungs is a liability, higher risk of N2 dissolving in blood stream)
Describe alveolar collapse in diving mammals
- Airway structures leading to the alveoli (site of gas exchange) are reinforced with structural stiffening cartilage
- This allows the lungs to collapse eliminating gas exchange and preventing N2 from accumulating in the blood and tissues
Are marine mammals immune to the bends?
- Not really…
- There is evidence that marine mammals can suffer from decompression sickness
- Instead of minimizing N2 load marine mammals may manage N2 load
What are some adaptations for O2 conservation during apnea?
- Bradycardia
- Peripheral vasoconstriction
- Increased O2 storage capacity (high blood volumes with high concentration of O2)
Do deep diving marine mammals have large or small lungs?
Small
Large lungs = too much air = liability (more likely to absorb N2)
How can deep diving mammals enhance their O2 storage?
Store O2 in blood instead of lungs
Deeper diving mammals store more O2 in blood
What are some old methods of studying diving physiology?
- Restrained animals in a laboratory
- Free-diving captive animals
- Accelerometers
Describe the Scholander Diving Response (“textbook diving response”)
- Cessation of breathing
- Pronounced bradycardia
- Reduced distribution of cardiac output
- Selective ischemia through regional vasoconstriction
- Maintenance of blood flow to vital organs
- Anaerobic metabolism after O2 supplies is depleted
- Accumulation of products of anaerobic metabolism (lactic acid)
What is wrong with this study
What are some new methods of studying diving physiology?
- Time-depth recorder (TDRs)
- Real time physiological monitoring (video cameras, drones)
Describe the diving response of Weddell Seals (more accurate)
- Cessation of breathing
- Variable bradycardia depending on dive duration
- Variable ischemia through regional vasoconstriction
- Maintenance of blood flow to vital organs
- Anaerobic metabolism after O2 supplies = depleted (only on very long dives)
- Accumulation of products of anaerobic metabolism (only in very long dives)
Describe the Aerobic Dive Limit
The maximum breath-hold without an increase in blood lactic acid concentration during or after a dive
What does the ADL depend on?
- Stored oxygen reserves
- Oxygen consumption rate
- Degree of peripheral vasoconstriction
- Rate of lactic acid production and consumption
How can extreme deep divers exceed ADL without an increase in blood lactic acid levels?
Extreme bradycardia
How can beaked whales which are relatively small in size undertake extreme deep dives without an increase in blood lactic acid levels?
- Dive duration typically increases with body size (larger animals = more O2 storage)
- Beaked whales = smaller body mass because tissues (brain, heart, lungs) are metabolically expensive
- Skin, bone, muscles = metabolically inexpensive
- Majority of body mass = made up of bone and muscle
- Unique muscle feature: Glycolytic fibers (important oxygen storage)
How does gliding affect the dive depth of marine mammals?
As dive depth increases, percentage of glide time for marine mammals increases
Dives incorporating prolonged gliding = less energetically costly than stroking dives (drop in O2 consumption)
