Saturday, April 3, 2010
Mammalian Diving Reflex
Mammalian diving reflex optimizes respiration to allow mammals to stay underwater for extended periods of time. When an animal's face comes in contact with cold water, a reflex is triggered that may lower heart rate, induce vasoconstriction, or shift blood around the body. Humans, being mammals, have may exercise this reflex to some extent, but to one not nearly as adept as that of seals, which may lower their heart rate from 125 to as low as 10 beats per minute. From our circulation unit, how is it possible that the heart muscle may still supply the body with oxygen? Does this make reptiles (such as alligators) similar to mammals? And, how is it possible that two species that diverged much earlier than the aquatic animals which returned to water both display traits that are beneficial towards survival in cold water submersion via the face? Why is it that humans may only exercise such a reflex to the limited extent? What may have caused this limitation?