Cardiac Physiology Lecture Review

Question-and-answer flashcards covering major concepts from Chapters 1-8, including cardiac cycle events, electrical activity, pressure–volume relationships, Frank–Starling mechanism, autonomic regulation, and hemodynamic equations.

Which vessel returns blood to the heart from the lower part of the body?

The inferior vena cava.

Where does blood carried by the pulmonary artery go, and is it oxygenated or de-oxygenated?

It goes to the lungs and is de-oxygenated.

True or false: Blood arriving via the pulmonary veins is oxygen-rich.

True – pulmonary veins return oxygenated blood from the lungs to the left atrium.

What arteries supply oxygenated blood to the head?

The carotid arteries.

What pressure relationship causes the aortic semilunar valve to open?

Left-ventricular pressure must exceed aortic pressure.

What causes the first heart sound (S1)?

Closure of the atrioventricular (AV) valves and opening of the semilunar valves.

What causes the second heart sound (S2)?

Closure of the semilunar valves and opening of the AV valves.

Define stroke volume (SV).

SV = End-diastolic volume (EDV) – End-systolic volume (ESV).

If EDV = 130 mL and ESV = 50 mL, what is stroke volume?

80 mL.

What ECG wave represents atrial depolarization?

The P wave.

What electrical event is hidden within the QRS complex?

Atrial repolarization.

At a heart rate of 60 bpm, how long is one cardiac cycle, and how is it divided?

1 second total: roughly 0.33 s systole and 0.67 s diastole.

During which two phases are ALL heart valves closed?

Isovolumetric contraction and isovolumetric relaxation.

State the Frank–Starling law in one sentence.

Increased myocardial stretch (greater EDV) leads to a stronger force of contraction and a larger stroke volume.

Define preload and afterload.

Preload: ventricular filling/EDV. Afterload: the pressure the left ventricle must overcome to eject blood (arterial resistance).

What neurotransmitter is most responsible for increasing cardiac contractility during sympathetic stimulation?

Norepinephrine.

Give the formula for cardiac output (Q̇).

Cardiac output = Heart rate × Stroke volume.

How is mean arterial pressure (MAP) calculated from cardiac variables?

MAP = Cardiac output × Total peripheral resistance (TPR).

Write the clinical formula for MAP using blood-pressure values.

MAP ≈ Diastolic BP + 1⁄3(Systolic BP – Diastolic BP).

List four mechanisms that enhance venous return during exercise.

1. Skeletal-muscle pump, 2. Respiratory (ventilatory) pump, 3. Venoconstriction, 4. One-way venous valves preventing backflow.

Why can people survive atrial arrhythmias more easily than ventricular arrhythmias?

Because 70-80 % of ventricular filling is passive; loss of the atrial ‘kick’ still allows adequate EDV, whereas ventricular failure stops systemic flow.

What is a normal ejection fraction, and how is it calculated?

About 55–60 % or higher; EF = (SV / EDV) × 100 %.

How does systemic hypertension affect left-ventricular workload?

It raises aortic pressure, so the LV must generate higher pressure (afterload) to eject blood, increasing myocardial work.

During exercise, which branch of the autonomic nervous system elevates heart rate above ~100 bpm?

The sympathetic nervous system.

What immediate neural change raises heart rate at the onset of exercise?

Withdrawal of parasympathetic (vagal) tone.

Why does blood flow preferentially increase to working skeletal muscle during exercise?

Local vasodilation in active muscles and vasoconstriction in non-essential regions redistribute cardiac output to match metabolic demand.

Why must right- and left-ventricular outputs remain equal in a healthy heart?

Because the circulatory system is closed; any sustained imbalance would cause pulmonary or systemic congestion.

In a pressure-volume loop, what does the width of the loop represent?

Stroke volume – the change in ventricular volume during ejection.

Name two unique features of the pulmonary circulation relative to systemic circulation discussed in class.

1. Pulmonary artery carries de-oxygenated blood. 2. Pulmonary veins carry oxygenated blood.

What typical blood-pressure values define systolic and diastolic pressure at rest?

Approximately 120 mm Hg systolic and 80 mm Hg diastolic (≤120/80 is considered normal).