BIOL 2251: QUIZ #3 HEART

Where is the heart located?

In the mediastinum, which is located in the thoracic cavity.

What are the three layers of the heart wall?

Epicardium, myocardium, and endocardium.

What is the function of the chordae tendineae?

They anchor the cusps of AV valves to papillary muscles and prevent valve inversion.

What is the purpose of the pericardial cavity?

It contains serous fluid to reduce friction during heartbeats.

What valve lies between the left atrium and left ventricle?

The mitral (bicuspid) valve.

Trace the path of blood from the right atrium to the lungs.

Right atrium → tricuspid valve → right ventricle → pulmonary semilunar valve → pulmonary trunk → pulmonary arteries → lungs.

What vessels bring oxygenated blood from the lungs to the heart?

Pulmonary veins.

Which chamber pumps blood into the systemic circulation?

Left ventricle.

What does the anterior interventricular artery supply?

The anterior surface of both ventricles.

What collects venous blood and returns it to the right atrium?

The coronary sinus.

What is the pacemaker of the heart?

The sinoatrial (SA) node.

What is the order of conduction in the heart?

SA node → AV node → AV bundle → bundle branches → Purkinje fibers.

What is the intrinsic rate of the SA node?

70–80 beats per minute.

What does the P wave represent on an ECG?

Atrial depolarization.

What causes rapid depolarization in cardiac muscle cells?

The opening of voltage-gated Na⁺ channels.

What condition is indicated when P waves and QRS complexes are not synchronized?

Atrioventricular block.

What is atrial systole?

Contraction of the atrial myocardium.

When are both sets of valves (AV and semilunar) closed?

During isovolumetric contraction and relaxation.

How is cardiac output calculated?

Heart rate × stroke volume.

What do heart sounds correspond to?

"Lub" is AV valves closing, "dup" is semilunar valves closing.

What is valvular stenosis?

A condition with stiff valve flaps that constrict blood flow.

What is pericarditis?

Inflammation of the pericardium, can cause fluid buildup and restrict heart function.

What is a unique feature of cardiac muscle compared to skeletal muscle?

Cardiac cells are branched and connected by intercalated discs.

What allows the heart to contract as a unit?

Gap junctions in intercalated discs enable functional syncytium.

Which nerve decreases heart rate?

The vagus nerve (parasympathetic).

What center in the brain regulates heart rate?

The cardiac center of the medulla oblongata.

Which system increases heart rate and contractility?

The sympathetic nervous system.

What is myocardial infarction?

A heart attack due to complete blockage of coronary arteries.

What is angina pectoris?

Chest pain due to reduced blood flow to the myocardium.

What triggers pacemaker cell depolarization?

Influx of Ca²⁺ through fast voltage-gated calcium channels.

What is the resting membrane potential of a nodal cell?

Approximately -60 mV.

What causes repolarization in pacemaker cells?

Efflux of K⁺ through voltage-gated potassium channels.

What event initiates ventricular systole?

Ventricular depolarization (QRS complex).

When does ventricular ejection occur?

When ventricular pressure exceeds arterial pressure and semilunar valves open.

What is the PR interval?

The time from atrial depolarization to ventricular depolarization.

When do AV valves close?

At the start of ventricular systole.

What prevents backflow from arteries into ventricles?

Semilunar valves.

What is the Frank-Starling Law?

Increased venous return increases stroke volume due to stretch of cardiac muscle.

What affects stroke volume?

Preload, afterload, and contractility.

What is congestive heart failure?

Impaired ability of the heart to pump blood effectively.

What side heart failure leads to pulmonary edema?

Left-sided heart failure.

What side heart failure leads to systemic edema?

Right-sided heart failure.

What is the function of the fibrous skeleton of the heart?

It anchors valves, provides structural support, and acts as an electrical insulator.

Which chamber has the thickest myocardium and why?

The left ventricle, because it must generate high pressure to pump blood through systemic circulation.

What causes the "lub" sound of the heartbeat?

The closing of AV valves during ventricular contraction.

What causes the "dup" sound of the heartbeat?

The closing of semilunar valves during ventricular relaxation.

What does the QRS complex represent?

Ventricular depolarization.

What does the T wave represent?

Ventricular repolarization.

What is the role of the AV node in conduction?

It delays the impulse to allow atrial contraction before ventricular contraction.

What is vagal tone?

Parasympathetic stimulation that slows the resting heart rate below the SA node's inherent rhythm.