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Mean arterial pressure rises during a stressful event, but blood flow through the brain barely changes. Cerebral vessels respond directly to the increased stretch on their walls. What did they do?

A patient has an end diastolic volume of 130 ml, an end systolic volume of 55 ml, and a heart rate of 72 beats per minute. What is the cardiac output?

At one instant in the cardiac cycle, left ventricular pressure is 46 mm Hg and rising, left atrial pressure is 7 mm Hg, aortic pressure is 79 mm Hg, and left ventricular volume is unchanged at 130 ml. Which phase is this?

An arteriole constricts until its radius is one third of its original value. Nothing else changes. Resistance to flow through that arteriole increases by a factor of about

A patient’s blood pressure reads 148/88 mm Hg. What is the mean arterial pressure?

A soldier stands rigidly at attention in the heat for a long period and faints. Which sequence best explains the faint?

An angiogram shows a blockage in the anterior interventricular artery close to its origin. Which region of the heart is at greatest risk?

An ECG strip shows regularly spaced P waves at 90 per minute. Only every second P wave is followed by a QRS complex, and each QRS that does appear is normal in shape. What is the most reasonable interpretation?

In an animal study the vagus nerves to the heart are cut. Resting heart rate rises from 75 to about 100 beats per minute and stays there. Which statement best explains the result?

The cardiac skeleton is a crisscrossing layer of connective tissue that surrounds the valves and separates atrial from ventricular musculature. Suppose this layer were replaced by ordinary cardiac muscle joined by gap junctions. What would be the most immediate consequence?