A Deeper Dive into the Mammalian Dive Reflex

As part of our shared evolutionary path, humans have something in common with seals: the mammalian dive response. While not as pronounced, this ability makes human excellent divers (as far as landlubbers go). Modern science is now showing us that this response is somewhat different in humans.

Mammalian Dive Reflex: Human vs. Seal

Where does the blood go during a long breath hold?Once you become addicted to the thrill of breath holding, you’ll meet your inner dolphin.This is what Stig calls the mammalian dive reflex (MDR)During this reflex, the body goes through a series of changes to deal with the low oxygen.These changes are:

• Bradycardia (lower heart rate)
• Vasoconstriction (narrowing of blood vessels)
• Blood shift (from extremities to vital organs)

For the longest time, scientists believed this mechanic to be similar to seals.And for the most part it is.

Big Heart. Big Brains

New research shows one big difference.With humans, the blood shift does not redirect (unlike seals) to the heart, but to the brain.When you look at the anatomy of a seal, it makes sense.The heart of a seal is, in comparison to its body, much larger than a human.And us humans have big brains, in comparison to our body.Click here to read the full study.