Dive Reflex

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A reflex is defined as an involuntary graded response to a specific stimulus. A dive reflex may be defined as pattern of reflexes triggered by the act of apnea. The two most noteworthy signs of dive reflex are bradycardia (slowing of the heart rate, or HR), and peripheral vasoconstriction (reduction of limb blood flow). Bradycardia results from increased parasympathetic stimuli. Peripheral vasoconstriction is from increased activity of the sympathetic nerves that supply blood to the arms and legs. The dive reflex is a mechanism for conserving oxygen during submersion. Oxygen consumption is focused to the essential organs needed for survival. Due to surface area to volume ratio, the less area exposed to the cold the higher the survival rate. The reflex is not as obvious in humans as in natural divers such as a seal. The reflex is produced by the combination of water touching the face and apnea. We hypothesized that the dive reflex would only be initiated by the combination of apnea in cold water. Seven experiments were preformed to test which conditions would elicit the dive reflex. The conditions of each experiment were as follows: 1) sitting in chair while breathing with and without apnea, 2) Submersion of face in cold water (12-15°C) with apnea, 3) Submersion of face in cold Water (12-15°C) without apnea, 4) Submersion of arm in cold water (12-15°C) with apnea, 5) Submersion of arm in cold water (12-15°C) without apnea, 6) Submersion of face in warm water (30°C) with apnea, 7) Submersion of face in warm water (30°C) without apnea. All seven experiments used a parameter of a 30-second resting period before submersion and a 30-second stimulus exposure. After each experiment there was a five minute recovery period to allow the physiological conditions to normalize. The results are stated as resting heart rate and total percent change from resting rate for each experiment: 1) 80 beats per minute (BPM), -2.25% 2) 71 BPM, -32.5% 3) 90 BPM, -15.54% 4) 74 BPM, 13.06%...
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