The Marine Mammal Diving Reflex
Introduction:
Just like us, all marine mammals, such as seals, whales, and sea lions must breathe air to get their oxygen. Humans have been known to hold their breath for up to 6 minutes (although not while diving). Some human divers can dive to 30 or 60 meters while holding their breath for about a minute. However some marine mammals can hod their breath for 30 minutes or longer while they dive.
Marine mammals have special adaptations which allow them to be able to stay down for so long. First, when marine mammals are on the surface of the water, they often breathe very quickly (hyperventilate). They will then hold their breath for a long time before they breathe again. The muscles of many marine mammals can work for a long time without oxygen. Our muscles cramp up if they do not get oxygen. The muscles of marine mammals do not.
Many marine mammals can save oxygen by shutting down the blood vessels that go to unnecessary organs. Blood goes mainly to the most important organ like the heart and brain. maiden mammals can slow their heartbeat while diving, saving oxygen. Whales can slow their heart rates as much as half as fast as normal. Seals are even more dramatic. Their normal resting rate is 100-150 beats/minute. This drops to about 10 beats/minute while diving. These special adaptations are called the marine mammal diving reflex. What sets off this diving reflex is not completely understood. Some scientist think it may have to do with sensors in the face and possibly in the respiratory system.
Physiological changes of a harbor seal during and after a dive
Although we are not marine mammals, we share some of the same characteristics. The diving reflex does happen to humans but its effects are much less that with seals or whales. In this experiment, we will see if we can observe the reflex in one person in your group. We will take that person's resting pulse. Then they will "dive" by holding their breath and placing their face in cold water for as long as they can. We will take their pulse using probeware while they are under water. We will observe the effect that the water has on their pulse rate. We will compare this with the control group. The control group will hold their breath but not place their faces in water. Be careful not to wet the computer equipment.