Involuntary coughing is the result of irritation of special sensory nerves in the respiratory tract. This helps to clear potentially damaging substances from the lungs (water, foreign bodies, dust, infection, mucous, etc.). Coughing can be more deleterious than helpful, causing discomfort, preventing sleep, or leading, in some cases, to dizziness or loss of consciousness (known as cough syncope).

The physiologic effects resulting from a cough are numerous. There is marked increase in intrathoracic pressure just prior to expulsion of air. When blood pressure is normal, this leads to a decrease in venous return to the right side of the heart and a decrease in cardiac output. On the other hand, a cough-induced increase in intrathoracic pressure may provide a form of “internal cardiopulmonary resuscitation” in a heart attack victim whose blood pressure is falling dangerously low. In this case, coughing can be as effective as the external chest compressions of CPR in raising blood pressure and providing better blood circulation to vital tissues.

In this experiment, you will observe the response of heart rate to coughing, and correlate this response to activity in the autonomic nervous systems.


In this experiment, you will

  • Obtain graphical representation of the heart rate at rest.
  • Observe the change in heart rate that occurs with repetitive coughing.
  • Correlate heart rate response to autonomic nervous system activity.