Cardiovascular Physiology – Exercise & Coronary Dynamics

These flashcards cover key lecture topics: MAP weighting, blood-flow redistribution during exercise, coronary artery oxygen extraction, sympathetic effects on heart dynamics, autoregulation, functional sympatholysis, and determinants of myocardial oxygen consumption.

Which blood-pressure component (systolic or diastolic) has a larger influence on Mean Arterial Pressure (MAP), and why?

Diastolic pressure, because the heart spends about two-thirds of the cardiac cycle in diastole and only one-third in systole.

In a normal cardiac cycle, what fraction of time is spent in systole versus diastole?

Approximately one-third in systole and two-thirds in diastole.

Using 120/80 mm Hg as an example, calculate MAP with the simple formula (SBP–DBP)/3 + DBP.

MAP ≈ (120−80)/3 + 80 = 40/3 + 80 ≈ 93 mm Hg.

At rest, roughly how much of the 5 L · min⁻¹ cardiac output is directed to skeletal muscle?

About 15–20 % of resting cardiac output.

During heavy exercise, what percentage of total cardiac output can be redirected to working skeletal muscle?

Approximately 80–85 %, depending on the individual.

What happens to blood flow to the gastrointestinal (GI) tract when you transition from rest to intense exercise?

It drops from about 20 % of cardiac output to roughly 3 %.

Immediately after intense exercise, would you expect cognitive function to be increased or decreased, and why?

Decreased, because cerebral blood flow is transiently lower during and immediately after exercise.

Why does stroke risk transiently rise during vigorous exercise?

Elevated arterial blood pressure places extra stress on fragile cerebral microvessels, increasing the chance of rupture.

How much oxygen do coronary arteries extract from the blood at rest?

Roughly 60–70 % of the delivered oxygen, indicating high myocardial metabolic demand.

Which branch vessels deliver oxygenated blood directly to the heart muscle?

The right and left coronary arteries and their branches.

Define the inotropic effect in the context of sympathetic stimulation.

An increase in the force of cardiac contraction caused by sympathetic nervous system activity.

How does a high heart rate affect diastolic filling time and potential stroke volume?

Higher heart rate shortens diastole, reducing filling time and potentially lowering stroke volume.

During graded exercise, why can both heart rate and stroke volume rise even though filling time shortens?

Sympathetic stimulation increases contractility, allowing greater ejection; stroke volume rises until it plateaus at ~50–70 % of VO₂ max.

What is autoregulation in coronary circulation?

The heart’s ability to maintain stable blood flow despite changes in perfusion pressure.

Explain functional sympatholysis in one sentence.

Local metabolites override sympathetic vasoconstriction, causing vasodilation to ensure adequate blood flow to active tissue.

What type of metabolism (aerobic or anaerobic) does the myocardium rely on almost exclusively, and why?

Aerobic metabolism, because the heart’s continuous activity requires a sustained, oxygen-rich energy supply.

During which phase of the cardiac cycle does about 50 % of myocardial oxygen consumption occur, and why?

During isovolumetric contraction, owing to the very high force and pressure development needed before ejection.

How does elevated systemic blood pressure (afterload) affect myocardial oxygen consumption?

Higher afterload forces the heart to work harder, increasing myocardial oxygen consumption.