Chapter 19 – Cardiovascular System: Heart

70 question-and-answer flashcards covering key concepts from Chapter 19 of McGraw-Hill’s Cardiovascular System: Heart lecture notes.

What two major components make up the cardiovascular system?

The heart and blood vessels.

What is perfusion?

Delivery of blood per time per gram of tissue (mL/min/g).

Why are continual heart pumping and open, healthy vessels necessary?

To provide adequate perfusion and maintain cellular health.

Name the three main types of blood vessels.

Arteries, veins, and capillaries.

How many chambers does the human heart contain?

Four chambers.

Which chambers are known as the pumping chambers?

The ventricles.

Which ventricle has the thickest wall and why?

The left ventricle, because it must generate high pressure for systemic circulation.

List the three layers of the heart wall from outermost to innermost.

Epicardium, myocardium, endocardium.

What is the primary function of heart valves?

To ensure one-way flow of blood through the heart.

Which valves are classified as atrioventricular (AV) valves?

The tricuspid valve and the bicuspid (mitral) valve.

When do AV valves close?

When the ventricles contract and force blood superiorly.

What structures prevent AV valve cusps from inverting into the atria?

Papillary muscles and chordae tendineae.

Name the two semilunar valves.

Pulmonary semilunar valve and aortic semilunar valve.

When do semilunar valves open?

When ventricular pressure exceeds arterial pressure during contraction.

What is valvular insufficiency?

Leaking of cardiac valves due to cusps not closing tightly, causing regurgitation.

What is valvular stenosis?

Scarring that prevents valve cusps from opening completely, restricting blood flow.

List four functions of the heart’s fibrous skeleton.

Provides structural support, anchors valves, offers framework for muscle attachment, and serves as an electrical insulator.

How is ventricular muscle contraction described due to its spiral arrangement?

It resembles wringing a mop, starting at the apex and compressing upward.

What vessels supply oxygenated blood to the heart wall?

Coronary arteries.

Why is coronary blood flow intermittent?

Vessels are open when the heart relaxes but compressed during contraction.

What is a functional end artery?

An artery whose blockage cannot be fully compensated by small anastomoses.

Define coronary heart disease.

Atherosclerotic plaque buildup in coronary arteries that reduces myocardial blood flow.

What is angina pectoris?

Chest pain from transient myocardial ischemia during exertion.

What defines a myocardial infarction?

Sudden, complete occlusion of a coronary artery causing possible heart muscle death.

What are intercalated discs?

Junctions containing desmosomes and gap junctions that connect cardiac muscle cells.

What is a functional syncytium?

A mass of electrically coupled cardiac cells acting as a single unit.

Why does cardiac muscle rely heavily on aerobic metabolism?

High energy demand and abundant mitochondria make it sensitive to low oxygen.

What is the heart’s conduction system?

Specialized cells that generate and transmit action potentials to coordinate contraction.

Which node serves as the natural pacemaker?

The sinoatrial (SA) node.

Where is the cardiac center located and what is its role?

In the medulla oblongata; it modulates heart rate and force via autonomic pathways.

Name the two divisions of the cardiac center.

Cardioacceleratory (sympathetic) and cardioinhibitory (parasympathetic) centers.

What keeps resting heart rate below the SA node’s intrinsic 100 bpm?

Parasympathetic vagal tone.

What is the typical intrinsic firing rate of the SA node in the body?

About 75 beats per minute.

What is special about Purkinje fibers?

Their large diameter enables rapid action potential conduction for synchronous ventricular contraction.

Why are papillary muscles activated prior to a rise in ventricular pressure?

To tense chordae tendineae, preventing AV valve prolapse during contraction.

Define ectopic pacemaker.

A pacemaker site outside the SA node that initiates heart rhythm.

What heart rate does the AV node generate if it becomes the pacemaker?

Approximately 40–50 beats per minute.

What prevents cardiac muscle from entering tetany?

A long refractory period (~250 ms) due to the plateau phase of its action potential.

What does an electrocardiogram (ECG) measure?

Electrical activity of cardiac muscle recorded from the body surface.

What does a first-degree AV block indicate?

Prolonged PR interval reflecting slowed conduction between atria and ventricles.

Describe ventricular fibrillation.

Chaotic ventricular electrical activity causing pump failure; requires defibrillation.

Define systole and diastole.

Systole = contraction; diastole = relaxation of heart chambers.

During which phase are all valves closed while ventricles contract but no blood is ejected?

Isovolumic contraction.

What is stroke volume (SV)?

The volume of blood ejected by a ventricle in one contraction.

How is end-systolic volume (ESV) defined?

Blood remaining in a ventricle after it contracts.

What causes the first heart sound (S1)?

Closure of the atrioventricular valves.

What is a heart murmur?

An abnormal sound from turbulent blood flow through the heart.

What is cardiac output (CO)?

The amount of blood pumped by one ventricle in one minute.

Provide the equation for cardiac output.

CO = Heart Rate (HR) × Stroke Volume (SV).

What is cardiac reserve?

The difference between maximal and resting cardiac output.

What are chronotropic agents?

Factors that change heart rate by influencing SA or AV node activity.

How do beta-blockers affect heart rate?

They act as negative chronotropic agents by blocking epinephrine/norepinephrine at beta receptors.

What is the atrial (Bainbridge) reflex?

A rise in heart rate triggered by stretch receptors in the atria when venous return increases.

Name three factors that influence stroke volume.

Venous return, inotropic agents (contractility), and afterload.

Explain the Frank-Starling law of the heart.

Greater ventricular filling leads to stronger contraction and higher stroke volume.

What is a positive inotropic agent?

A substance that increases contractility by elevating intracellular Ca²⁺.

Define afterload.

The pressure in arteries that ventricles must overcome to eject blood.

How does increased afterload affect stroke volume?

It decreases stroke volume by making ejection more difficult.

What is bradycardia?

A persistently low resting heart rate below 60 bpm in adults.

List two possible causes of tachycardia.

Heart disease, fever, anxiety (any two accepted).

At what embryonic day does the primitive heart tube begin to beat?

Around day 22 of development.

From which germ layer do the heart tubes develop?

Mesoderm.

What fetal opening allows blood to pass from right atrium to left atrium before birth?

The foramen ovale.

What is the adult remnant of the foramen ovale called?

The fossa ovalis.

Why is the left side of the heart stronger than the right?

It must pump blood through systemic circulation, requiring higher pressure.

What are the two main normal heart sounds and what do they represent?

"Lubb" (S1) is AV valve closure; "dupp" (S2) is semilunar valve closure.

What is the functional unit formed by electrically connected cardiac cells called?

A functional syncytium.

Which receptors provide the cardiac center with blood-pressure information?

Baroreceptors.

Which coronary veins return deoxygenated blood directly to the right atrium?

Cardiac veins (e.g., great, middle, small) via the coronary sinus.

What happens to coronary vessels during ventricular contraction?

They are compressed, temporarily reducing coronary blood flow.