The diving reflex may allow a person to survive extended periods of submersion in cold water due to which physiologic response?

The diving reflex may allow a person to survive extended periods of submersion in cold water due to which physiologic response?

• A. Bradycardia and slowing of the metabolic rate
• B. Tachycardia and increased metabolic rate
• C. Vasodilation of peripheral vessels
• D. Increased respiratory rate

Answer: (A)

The diving reflex works by conserving oxygen during submersion. When cold water touches the face, the body responds with a slower heart rate (bradycardia) and a reduction in metabolic rate. Slower heart rate means the heart uses less oxygen per minute, and a lower metabolic rate further decreases overall oxygen consumption. Together, these changes extend how long someone can stay submerged by prioritizing oxygen delivery to vital organs like the brain and heart, while nonessential tissues receive less blood flow through peripheral vasoconstriction. Other responses listed wouldn’t support survival during submersion: increasing heart rate would raise oxygen demand, dilation of peripheral vessels would waste oxygen by improving blood flow to nonessential areas, and increasing breathing is inconsistent with the reflex, which often includes apnea.

The diving reflex works by conserving oxygen during submersion. When cold water touches the face, the body responds with a slower heart rate (bradycardia) and a reduction in metabolic rate. Slower heart rate means the heart uses less oxygen per minute, and a lower metabolic rate further decreases overall oxygen consumption. Together, these changes extend how long someone can stay submerged by prioritizing oxygen delivery to vital organs like the brain and heart, while nonessential tissues receive less blood flow through peripheral vasoconstriction.

Other responses listed wouldn’t support survival during submersion: increasing heart rate would raise oxygen demand, dilation of peripheral vessels would waste oxygen by improving blood flow to nonessential areas, and increasing breathing is inconsistent with the reflex, which often includes apnea.