A 48-year-old man, who engaged in regular physical exercise, went to see his physician because of recurrent headaches. Physical examination revealed that the patient had a mean heart rate of 55 beats/min. His physician noted that the patient's cardiac rhythm varied substantially with the phases of respiration; the heart rate increased during inspiration and decreased during expiration. QUESTION: What changes in cardiac sympathetic and parasympathetic activity take place during the respiratory cycle? QUESTION: Are the respiratory fluctuations in heart rate produced by the rhythmic changes in sympathetic activity, in parasympathetic activity, or both? The physician diagnosed this patient's headaches as migraine. He advised the patient to take propranolol, a ß-adrenergic receptor antagonist, to relieve the headaches. The physician noted that after the patient had taken the propranolol, the mean heart rate diminished very slightly, and the respiratory fluctuations in heart rate were not appreciably different from those observed before the propranolol was taken. QUESTION: Does the failure of propranolol to induce a substantial change in mean heart rate or in the respiratory fluctuations in heart rate necessarily signify that the patient's cardiac sympathetic neural activity was negligible at the time he was being examined? Explain.
A 48-year-old man, who engaged in regular physical exercise, went to see his physician because of recurrent headaches. Physical examination revealed that the patient had a mean heart rate of 55 beats/min. His physician noted that the patient's cardiac rhythm varied substantially with the phases of respiration; the heart rate increased during inspiration and decreased during expiration. QUESTION: What changes in cardiac sympathetic and parasympathetic activity take place during the respiratory cycle? QUESTION: Are the respiratory fluctuations in heart rate produced by the rhythmic changes in sympathetic activity, in parasympathetic activity, or both? The physician diagnosed this patient's headaches as migraine. He advised the patient to take propranolol, a ß-adrenergic receptor antagonist, to relieve the headaches. The physician noted that after the patient had taken the propranolol, the mean heart rate diminished very slightly, and the respiratory fluctuations in heart rate were not appreciably different from those observed before the propranolol was taken. QUESTION: Does the failure of propranolol to induce a substantial change in mean heart rate or in the respiratory fluctuations in heart rate necessarily signify that the patient's cardiac sympathetic neural activity was negligible at the time he was being examined? Explain.
Human Anatomy & Physiology (11th Edition)
11th Edition
ISBN:9780134580999
Author:Elaine N. Marieb, Katja N. Hoehn
Publisher:Elaine N. Marieb, Katja N. Hoehn
Chapter1: The Human Body: An Orientation
Section: Chapter Questions
Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...
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Transcribed Image Text:A 48-year-old man, who engaged in regular physical exercise, went to see his physician
because of recurrent headaches. Physical examination revealed that the patient had a
mean heart rate of 55 beats/min. His physician noted that the patient's cardiac rhythm
varied substantially with the phases of respiration; the heart rate increased during
inspiration and decreased during expiration.
QUESTION: What changes in cardiac sympathetic and parasympathetic activity take
place during the respiratory cycle?
QUESTION: Are the respiratory fluctuations in heart rate produced by the rhythmic
changes in sympathetic activity, in parasympathetic activity, or both?
The physician diagnosed this patient's headaches as migraine. He advised the patient to
take propranolol, a ß-adrenergic receptor antagonist, to relieve the headaches. The
physician noted that after the patient had taken the propranolol, the mean heart rate
diminished very slightly, and the respiratory fluctuations in heart rate were not
appreciably different from those observed before the propranolol was taken.
QUESTION: Does the failure of propranolol to induce a substantial change in mean
heart rate or in the respiratory fluctuations in heart rate necessarily signify that the
patient's cardiac sympathetic neural activity was negligible at the time he was being
examined? Explain.
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