Thursday, March 3, 2016

The Master Switch Of Life

By Kristy McCaffrey

P.F. Scholander
In 1963, Per Scholander, a Swedish-born researcher working in the United States, discovered a Master Switch of Life in vertebrate animals—a defense against asphyxia. For humans, it’s a nod to our dormant amphibious reflexes. In simple terms, it’s the body’s response to being underwater. As soon as we place our faces in water, an onslaught of physiological reflexes affects our brain, lungs and heart. When your mother told you to “splash water on your face” during times of upset, she was on to something.

What happens to the human body as it enters an arena usually reserved for marine life? As a diver descends, blood begins flooding away from limbs and toward vital organs. This shunting—called peripheral vasoconstriction—from less important areas helps keep the brain and heart oxygenated longer, thereby extending the amount of time a diver can remain submerged. When a diver descends to 300 feet—a depth frequently reached by modern freedivers—vessels in the lungs engorge with blood, preventing them from collapse. The deeper a human descends, the stronger the peripheral vasoconstriction becomes. What’s curious is that Scholander found that a person need submerge only his face in water to activate these lifesaving reflexes. But these responses can only be triggered by water and it must be cooler than the surrounding air.

A freediver.

Today, freedivers exploit the Master Switch to their advantage, but it isn’t without risk. Here is what occurs in the body as a swimmer freedives:

First 30 feet: With the lungs full of air, the swimmer must paddle to descend.

Once past 30 feet: The pressure on the body doubles and the lungs shrink. The swimmer is now in neutral buoyancy and feels weightless. It’s here that something extraordinary happens—the ocean pulls the diver down. Swimming is no longer required.

At 100 feet: The pressure triples and the ocean’s surface is barely visible.

At 150 feet: The diver experiences high levels of carbon dioxide and nitrogen in the bloodstream, causing a dream-like state.

At 250 feet: The pressure is now so extreme that the lungs shrink to the size of a small apple and the heart beats at half its normal rate to conserve oxygen. Some freedivers report heartrates as low as 14 beats per minute

At 300 feet: This is where the Master Switch really kicks in. There is a free flow of blood and water into the thoracic cavity as the chest collapses to half its original size. The effects of nitrogen narcosis are so strong that divers forget where they are, what they’re doing, and why they’re in such a dark place. Hallucinations are common, as is the loss of motor control.

As a diver reverses and begins to ascend, the Master Switch also reverses. The heart rate increases and blood floods back into the veins and arteries and organs. However, the lungs ache to breathe and the vision fades. The chest convulses from the buildup of carbon dioxide. A diver must hurry or risk blacking out. If a black out occurs, a diver can stay submerged for up to two minutes. At the end of two minutes, the body will wake itself up and breathe one last time before death. If a diver has been rescued and carried to the surface by this time, he or she will inhale much-needed air and probably survive. If the person is still underwater, their lungs will fill with water and they’ll drown.

Humans connection to the ocean runs deep. In the womb, we grow within an amniotic fluid that is similar in makeup to ocean water. At one month, an embryo will grow fins first, then feet. At five weeks, that same embryo will have a 2-chambered heart, akin to a fish. Human blood has a chemical composition similar to seawater.
A blue whale.
Ancient cultures knew all about the Master Switch and employed it for centuries to harvest sponges, pearls, coral, and food hundreds of feet below the surface of the ocean. We carry within us latent abilities that connect us to the whales and dolphins, a key from our distant past.

Works Cited
“Freediving.” Wikipedia. <>
 Nestor, James. Deep. Mariner Books, 2014.
 Scholander, P. F. “The Master Switch of Life.” Scientific American Magazine. December 1963.

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