Diving Physiology

Question 1

Hypoxia

Answer 1

Decline of available O2

Question 2

Hypercapnia

Answer 2

Increase in CO2

Question 3

Asyphxia

Answer 3

Hypoxia + Hypercapnia = High CO2

Question 4

Acidosis

Answer 4

Accumulation of lactic acid

Question 5

Ischemia

Answer 5

Tissues deprived of circulating blood

Question 6

What are the two main challenges that diving marine mammals face?

Answer 6

1. Hydrostatic pressure
2. Oxygen conservation

Question 7

What is Boyle’s Law?

Answer 7

• Pressure and Volume are inversely proportional
• Pressure increases by 1 atm every 10m
  As volume increases, pressure decreases

Question 8

What is Henry’s Law?

Answer 8

The amount of dissolved gas in a liquid is proportional to the partial pressure above the liquid
As pressure increases, solubility increases

Question 9

How does Henry’s Law pose a problem for deep diving marine mammals?

Answer 9

The bends

Question 10

Describe the Bends (related to Henry’s Law)

Answer 10

• 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

Question 11

What are some reasons why marine mammals don’t get the bends?

Answer 11

1. Isolate N2 from the site of gas exchange (move air into upper airway where it is not in contact with blood)
2. Collapse lung (no gas exchange)
3. Exhale before diving (air in lungs is a liability, higher risk of N2 dissolving in blood stream)

Question 12

Describe alveolar collapse in diving mammals

Answer 12

• 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

Question 13

Are marine mammals immune to the bends?

Answer 13

• Not really…
• There is evidence that marine mammals can suffer from decompression sickness
• Instead of minimizing N2 load marine mammals may manage N2 load

Question 14

What are some adaptations for O2 conservation during apnea?

Answer 14

• Bradycardia
• Peripheral vasoconstriction
• Increased O2 storage capacity (high blood volumes with high concentration of O2)

Question 15

Do deep diving marine mammals have large or small lungs?

Answer 15

Small
Large lungs = too much air = liability (more likely to absorb N2)

Question 16

How can deep diving mammals enhance their O2 storage?

Answer 16

Store O2 in blood instead of lungs
Deeper diving mammals store more O2 in blood

Question 17

What are some old methods of studying diving physiology?

Answer 17

• Restrained animals in a laboratory
• Free-diving captive animals
• Accelerometers

Question 18

Describe the Scholander Diving Response (“textbook diving response”)

Answer 18

• 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

Question 19

What are some new methods of studying diving physiology?

Answer 19

• Time-depth recorder (TDRs)
• Real time physiological monitoring (video cameras, drones)

Question 20

Describe the diving response of Weddell Seals (more accurate)

Answer 20

• 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)

Question 21

Describe the Aerobic Dive Limit

Answer 21

The maximum breath-hold without an increase in blood lactic acid concentration during or after a dive

Question 22

What does the ADL depend on?

Answer 22

• Stored oxygen reserves
• Oxygen consumption rate
• Degree of peripheral vasoconstriction
• Rate of lactic acid production and consumption

Question 23

How can extreme deep divers exceed ADL without an increase in blood lactic acid levels?

Answer 23

Extreme bradycardia

Question 24

How can beaked whales which are relatively small in size undertake extreme deep dives without an increase in blood lactic acid levels?

Answer 24

• 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)

Question 25

How does gliding affect the dive depth of marine mammals?

Answer 25

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)*