In this lab, students measure and compare their normal heart rates while resting, holding their breath, and holding their breath as they submerge their faces in cool water to simulate the effects of the diving reflex. Here’s how it works:

  • Heart rate is monitored using a pulse plethysmograph placed on the student’s finger and connected to the TA control module
  • Students monitor their heart rate while resting and again while holding their breath (apnea) to establish a baseline
  • Students monitor their heart rate while submerging their face into 3 containers of cool water (at 5°, 15° and 25°C) and holding their breath for 20 seconds (diving reflex)
  • Data is collected and analyzed using LabScribe software

Students gain an understanding of the effects of the Diving Reflex as they see heart rate drop while their face is submerged in the cooler water. Students can also monitor the change in amplitude of the pulse which is a good measure of reduction of blood flow top the fingers.

The lab leads to an interesting discussion of why the built-in reflex mechanism slows heart rate and narrows the blood vessels so the oxygen rushes more to the brain and the heart.

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This lab is easy to perform and fun for students to test various hypotheses – and another reason why 68 of the top 100 colleges and universities in the U.S. use iWorx physiology lab equipment.

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