A 24-year-old medical student finds that he has a rapid heartbeat while taking an important examination. His temperature is 37°C (98.6°F), pulse is 110min, respirations are 15/min, and blood pressure is 140/80 mm Hg. Physical examination shows no other abnormalities. Which of the following changes in the resting membrane potential (phase 4) of the sinoatrial node is the cause of his increased heart rate? A) Hyperpolarization B) Increased length of the absolute refractory period C) Increased rate of depolarization D) Increased threshold E) Increased velocity of conduction

A 24-year-old medical student finds that he has a rapid heartbeat while taking an important examination. His temperature is 37°C (98.6°F), pulse is 110min, respirations are 15/min, and blood pressure is 140/80 mm Hg. Physical examination shows no other abnormalities. Which of the following changes in the resting membrane potential (phase 4) of the sinoatrial node is the cause of his increased heart rate? A) Hyperpolarization B) Increased length of the absolute refractory period C) Increased rate of depolarization D) Increased threshold E) Increased velocity of conduction

Human Physiology: From Cells to Systems (MindTap Course List)

9th Edition

ISBN:9781285866932

Author:Lauralee Sherwood

Publisher:Lauralee Sherwood

Chapter9: Cardiac Physiology

Section: Chapter Questions

Problem 10UC

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