Which structure is the tough outer sac that anchors the heart and keeps it from overfilling?
Fibrous pericardium
✓
Visceral pericardium
Endocardium
Myocardium
Correct Answer
Fibrous pericardium
The fibrous pericardium is a dense connective tissue sac that anchors the heart to surrounding structures and resists overexpansion. The visceral pericardium is the thin serous layer fused to the heart surface. Endocardium is the inner lining of the chambers. Myocardium is the muscular middle layer of the heart wall.
Category: Heart Anatomy
Question 2
Which vessel carries deoxygenated blood out of the heart toward the lungs?
Aorta
Pulmonary trunk
✓
Superior vena cava
Pulmonary veins
Correct Answer
Pulmonary trunk
The right ventricle ejects deoxygenated blood into the pulmonary trunk, which splits into the pulmonary arteries leading to the lungs. The aorta receives oxygenated blood from the left ventricle. The superior vena cava returns blood from the upper body to the right atrium. Pulmonary veins carry oxygenated blood from the lungs to the left atrium.
Category: Heart Anatomy
Question 3
Which valve keeps blood that has been ejected into the aorta from flowing back into the heart?
Mitral valve
Pulmonary valve
Aortic valve
✓
Tricuspid valve
Correct Answer
Aortic valve
The aortic semilunar valve sits at the exit of the left ventricle and closes when ventricular pressure falls below aortic pressure. The mitral valve separates the left atrium from the left ventricle. The pulmonary valve guards the exit of the right ventricle. The tricuspid valve separates the right atrium from the right ventricle.
Category: Heart Anatomy
Question 4
Which chamber of the heart has the thickest muscular wall?
Right atrium
Left atrium
Right ventricle
Left ventricle
✓
Correct Answer
Left ventricle
The left ventricle pumps blood through the entire systemic circuit against high resistance, so its myocardium is the thickest. The right atrium has a thin wall because it only moves blood into the right ventricle. The left atrium is also thin walled for the same reason. The right ventricle pumps only to the nearby, low-resistance pulmonary circuit, so its wall is thinner than the left.
Category: Heart Anatomy
Question 5
Into which chamber does the coronary sinus empty?
Right atrium
✓
Left atrium
Right ventricle
Left ventricle
Correct Answer
Right atrium
The coronary sinus collects deoxygenated blood from the cardiac veins and empties it into the right atrium, joining blood returned by the venae cavae. The left atrium receives oxygenated blood from the pulmonary veins. The right ventricle receives blood from the right atrium, not directly from the coronary sinus. The left ventricle receives blood from the left atrium.
Category: Heart Anatomy
Question 6
The anterior interventricular artery, often called the left anterior descending artery, branches from which vessel?
Right coronary artery
Left coronary artery
✓
Pulmonary trunk
Posterior interventricular artery
Correct Answer
Left coronary artery
The left coronary artery divides into the anterior interventricular artery and the circumflex artery. The right coronary artery gives rise to the marginal and posterior interventricular arteries. The pulmonary trunk carries blood to the lungs and supplies no coronary branches. The posterior interventricular artery runs on the back of the heart and is usually a branch of the right coronary artery.
Category: Heart Anatomy
Question 7
In the fetal heart, which structure connects the main pulmonary artery to the aorta so most blood bypasses the lungs?
Foramen ovale
Fossa ovalis
Ductus arteriosus
✓
Ligamentum arteriosum
Correct Answer
Ductus arteriosus
The ductus arteriosus connects the pulmonary trunk to the aorta so most blood bypasses the nonfunctional fetal lungs. The foramen ovale is an opening between the two atria. The fossa ovalis is the adult remnant of the foramen ovale. The ligamentum arteriosum is the fibrous adult remnant of the ductus arteriosus.
Category: Heart Development
Question 8
After an impulse leaves the AV node, which structure does it travel through next?
Purkinje fibers
Bundle branches
Internodal pathways
Atrioventricular bundle
✓
Correct Answer
Atrioventricular bundle
From the AV node the impulse enters the atrioventricular bundle, also called the bundle of His, which passes through the fibrous skeleton into the interventricular septum. Purkinje fibers are the last part of the pathway, spreading the impulse through the ventricular walls. Bundle branches come after the atrioventricular bundle. Internodal pathways carry the impulse from the SA node to the AV node, before it.
Category: Conduction System
Question 9
Which ECG feature represents depolarization of the ventricles?
QRS complex
✓
P wave
T wave
PR interval
Correct Answer
QRS complex
The QRS complex records the rapid depolarization of the ventricular muscle mass, which is why it is the largest deflection. The P wave represents atrial depolarization. The T wave represents ventricular repolarization. The PR interval spans from the start of atrial depolarization to the start of ventricular depolarization.
Category: Conduction System
Question 10
What does the brief delay of the impulse at the AV node accomplish?
It lets the ventricles repolarize first
It lets the atria finish contracting first
✓
It stops the SA node from firing again
It raises the force of ventricular contraction
Correct Answer
It lets the atria finish contracting first
Slow conduction through the AV node gives the atria time to finish contracting and push their blood into the ventricles before ventricular contraction begins. Ventricular repolarization happens later in the cycle and is not the purpose of the delay. The SA node keeps firing on its own schedule regardless of the delay. The delay affects timing, not the strength of ventricular contraction.
Category: Conduction System
Question 11
Which ion rushes in through fast channels to cause the rapid depolarization phase of a contractile cardiac muscle cell?
Potassium
Calcium
Sodium
✓
Chloride
Correct Answer
Sodium
Fast voltage-gated sodium channels open and sodium floods in, producing the sharp upstroke of the contractile cell action potential. Potassium leaving the cell drives repolarization. Calcium entering through slow channels sustains the plateau that follows. Chloride does not drive the cardiac action potential upstroke.
Category: Cardiac Muscle
Question 12
Which structure electrically insulates the atria from the ventricles so impulses pass only through the AV node and bundle?
Interatrial septum
Parietal pericardium
Chordae tendineae
Fibrous skeleton
✓
Correct Answer
Fibrous skeleton
The fibrous skeleton is dense connective tissue around the valves that does not conduct impulses, so the only electrical route from atria to ventricles is the AV node and bundle. The interatrial septum separates the two atria from each other. The parietal pericardium lines the inside of the pericardial sac. Chordae tendineae are tendinous cords that anchor the AV valve cusps.
Category: Conduction System
Question 13
Which describes the heart valves during isovolumic ventricular contraction?
All four valves are closed
✓
All four valves are open
AV valves open, semilunar valves closed
AV valves closed, semilunar valves open
Correct Answer
All four valves are closed
At the start of ventricular systole, pressure rises enough to close the AV valves but not yet enough to open the semilunar valves, so all four are closed and ventricular volume stays the same. All four valves are never open at once in a normal heart. AV valves open with semilunar valves closed describes ventricular filling. AV valves closed with semilunar valves open describes ventricular ejection.
Category: Cardiac Cycle
Question 14
The first heart sound is produced mainly by the closure of which valves?
Semilunar valves
Atrioventricular valves
✓
Venous valves
Lymphatic valves
Correct Answer
Atrioventricular valves
The first heart sound, the lub, occurs at the start of ventricular systole when rising ventricular pressure snaps the atrioventricular valves shut. Semilunar valve closure produces the second heart sound. Venous valves are in the limb veins and make no heart sound. Lymphatic valves are in lymph vessels and are unrelated to heart sounds.
Category: Cardiac Cycle
Question 15
During which phase does most filling of the ventricles take place?
Atrial systole
Isovolumic contraction
Ventricular diastole
✓
Ventricular ejection
Correct Answer
Ventricular diastole
Most ventricular filling happens passively during ventricular diastole, as blood flows from the atria through the open AV valves. Atrial systole only tops off the ventricles with a smaller additional volume. During isovolumic contraction all valves are closed, so no filling occurs. During ventricular ejection blood is leaving the ventricles, not entering them.
Category: Cardiac Cycle
Question 16
Using end-diastolic volume (EDV) and end-systolic volume (ESV), how is stroke volume calculated?
EDV plus ESV
ESV minus EDV
EDV divided by ESV
EDV minus ESV
✓
Correct Answer
EDV minus ESV
Stroke volume is the blood ejected per beat, which is the volume before contraction minus the volume left afterward. EDV plus ESV has no physiological meaning. ESV minus EDV gives a negative number because ESV is the smaller volume. EDV divided by ESV is a ratio, not a volume.
Category: Cardiac Physiology
Question 17
According to the Frank-Starling mechanism, what happens when venous return to the heart increases?
Stroke volume increases
✓
Heart rate decreases
Stroke volume decreases
Afterload decreases
Correct Answer
Stroke volume increases
Greater venous return stretches the ventricular muscle more, and stretched fibers contract more forcefully, so stroke volume rises. Heart rate decreases is not a direct result of the Frank-Starling mechanism. Stroke volume decreases is the opposite of what increased stretch produces. Afterload decreases describes a change in arterial resistance, not a response to venous return.
Category: Cardiac Physiology
Question 18
Which change increases the afterload on the heart?
Increased venous return
Elevated arterial blood pressure
✓
Increased parasympathetic stimulation
Decreased heart rate
Correct Answer
Elevated arterial blood pressure
Afterload is the pressure the ventricle must overcome to open the semilunar valve, so higher arterial blood pressure raises it. Increased venous return raises preload, not afterload. Increased parasympathetic stimulation slows the heart rate and does not raise the pressure opposing ejection. Decreased heart rate changes filling time but does not raise the pressure opposing ejection.
Category: Cardiac Physiology
Question 19
Where are the cardiovascular centers that adjust heart rate through autonomic nerves located?
Hypothalamus
Cerebellum
Medulla oblongata
✓
Pons
Correct Answer
Medulla oblongata
The cardioaccelerator and cardioinhibitory centers in the medulla oblongata send sympathetic and parasympathetic signals to the heart. The hypothalamus can influence these centers but does not house them. The cerebellum coordinates movement and balance. The pons contains respiratory and other nuclei, not the main cardiovascular centers.
Category: Cardiac Physiology
Question 20
During embryonic development, the bulbus cordis gives rise to which heart chamber?
Right atrium
Left atrium
Left ventricle
Right ventricle
✓
Correct Answer
Right ventricle
The bulbus cordis of the primitive heart tube develops into the right ventricle. The right atrium forms partly from the sinus venosus and partly from the primitive atrium. The left atrium forms from the primitive atrium along with incorporated pulmonary veins. The left ventricle develops from the primitive ventricle.
Category: Heart Development