What physiological change occurs during the mammalian diving reflex?

The mammalian diving reflex triggers a series of physiological changes that are critical for survival during underwater breath-holding. One of the primary responses is a decreased heart rate, known as bradycardia. This reduction in heart rate serves to conserve oxygen by slowing the metabolic rate of the heart and allowing the body to prioritize oxygen supply to vital organs, such as the brain and heart, while redirecting blood flow away from less critical areas, such as the limbs. This reflex is especially pronounced in mammals, allowing them to dive for extended periods by efficiently managing their oxygen reserves.

In contrast, the other options do not align with the physiological responses associated with this reflex. Blood flow to limbs typically decreases rather than increases during the diving response, as the body prioritizes essential organs. Breathing is typically inhibited and reduced to a minimum during a dive, rather than being shallow and frequent. Lastly, metabolic rate does not increase; instead, the body goes into a conservation mode to utilize oxygen more efficiently, which may even lead to a reduced metabolic rate during dives.