Diving Responses: Fact or Fiction

The classical concept of the diving response emphasizes the observed selective vasoconstriction and bradycardia. It has recently been questioned, however, whether these responses can be considered normal reflex adjustments to diving because animals, when they dive voluntarily, usually show much less bradycardia, and presumably less vasoconstriction, than when they are forcibly submerged. These apparent differences in the expression of the responses to submergence may be less important than appear at first glance. </jats:p