Diving mammals Flashcards
What is the difference between a voluntary and involuntary dive?
Voluntary would be for things like looking for food and playing, and involuntary would be for escaping from predators
What are the 3 things that need to be considered for determining how long an animal can dive for?
- O2 available for the animal
- Potential of the animal to adjust its cardiovascular physiology
- Potential of the animal to adjust its metabolism to reduce oxygen requirements
How do diving mammals control the oxygen available for diving?
Controlled apnea: suppression of respiratory muscle action and breathing control systems
How are diving mammals able to reduce their lung volume while underwater?
The thorax is highly compressible, so the water pressure at greater depths will shove the thoracic walls in and compress the lungs
What other adaptation do marine mammals have to lower nitrogen buildup in their blood?
Forced alveolar collapse
Where do the gases go when a diving mammal does a forced alveolar collapse?
Away from the respiratory surfaces and into the conducting surfaces
How does the forced alveolar collapse prevent decompression sickness in marine mammals?
By forcing the gases into the conducting airways, the blood isn’t as exposed to the increasing nitrogen pressure in the lungs, which stops it from building up in the blood and tissues
How much of the alveolar collapse occurs in a mammal diving at moderate depths?
Incomplete collapse
How much of the alveolar collapse occurs in a mammal diving at deep depths?
Complete collapse
Why aren’t dolphins affected by decompression sickness when they do repeated dives to moderate depths?
They do have nitrogen buildup in their blood, but they are adapted to the high levels that would be fatal for us
Why are humans susceptible to decompression sickness when diving?
We don’t have the flexible thoracic cavity to allow lung compression, and we can’t do the forced alveolar collapse. The nitrogen just ends up in our blood and will come out in bubbles if we surface too fast
Why do some diving mammals exhale before a long, deep dive?
Avoid lung collapse and decompression sickness
What are the 3 ways oxygen is stored?
Lungs, in the blood attached to Hb, and in myoglobin
Where do we store most of our oxygen while diving?
Lungs
How do diving mammals store oxygen?
Mostly in myoglobin, since they have a lot more muscle than we do. They have a higher O2 carrying capacity and blood volume, so can also store a lot in their blood
How does the oxygen carrying capacity of the blood of marine mammals compare to ours?
Higher in marine mammals
How do the oxygen stores of mammals that make short and shallow dives compare to humans?
Is higher, but not much
How do the oxygen stores of mammals that make longer and deeper dives compare to humans?
Much higher
What is hypoperfusion?
Reduced blood flow through specific organs
What is bradycardia?
Reduced heart rate
Why wouldn’t it be good to be constantly sending blood to all organs during a dive?
Would quickly use up all the oxygen
How does blood flow get decreased to less important tissues during a dive?
Vasoconstriction, bradycardia, splenic contractions
What do splenic contractions do during a dive?
Produces more red blood cells
What happens to blood flow during an involuntary dive?
Blood stays in the heart-lung-brain circuit and is constantly shunted away from everything else. Blood flows from the right heart to the lungs, lungs to left heart, left heart to brain, brain to right heart
What happens to overall metabolism while diving?
Hypometabolism. Is suppressed overall and some tissues switch to anaerobic metabolism
Can the heart and brain do anaerobic metabolism?
No, they constantly need aerobic blood
Do the muscles switch over to anaerobic metabolism during a dive?
They will use up the oxygen stored in their myoglobin first then switch to glycolysis
What happens when the muscles switch to glycolysis?
They start to buildup lactic acid, but it stays low in the blood
What is the aerobic dive limit?
The longest an animal can stay underwater before lactic acid appears in the blood. Varies between animals
What happens to the lactic acid buildup in the muscles when the animal resurfaces?
The muscles release it into the blood and causes the lactic acid in the blood to spike, then it drops as it gets metabolized
What limits how long an animal can stay underwater?
Lactic acid buildup
What are the 7 diving response mechanisms in diving mammals?
- Apnea
- Oxygen storage
- Selective blood flow
- Bradycardia
- Splenic contraction
- Hypometabolism
- Anaerobic metabolism
