Which valve lies between the left atrium and the left ventricle?
Mitral valve
✓
Tricuspid valve
Aortic valve
Pulmonary valve
Correct Answer
Mitral valve
The mitral valve is the atrioventricular valve on the left side, opening so blood can flow from the left atrium into the left ventricle. The tricuspid valve sits between the right atrium and right ventricle. The aortic valve sits between the left ventricle and the aorta. The pulmonary valve sits between the right ventricle and the pulmonary artery.
Category: Heart Anatomy
Question 2
Which layer of the heart wall lines the chambers and covers the valves?
Myocardium
Endocardium
✓
Epicardium
Parietal pericardium
Correct Answer
Endocardium
The endocardium is the thin inner lining of the chambers and valves. The myocardium is the thick middle layer of cardiac muscle that contracts. The epicardium is the outer layer of the heart wall, the same as the visceral pericardium. The parietal pericardium is part of the sac around the heart, not the heart wall itself.
Category: Heart Anatomy
Question 3
Which vessels return oxygenated blood from the lungs to the left atrium?
Pulmonary arteries
Superior vena cava
Pulmonary veins
✓
Coronary arteries
Correct Answer
Pulmonary veins
The pulmonary veins carry freshly oxygenated blood from the lungs to the left atrium, an exception to the rule that veins carry deoxygenated blood. The pulmonary arteries carry deoxygenated blood from the right ventricle to the lungs. The superior vena cava returns deoxygenated blood from the upper body to the right atrium. The coronary arteries supply the heart muscle itself.
Category: Blood Flow and Vessels
Question 4
Why is the wall of the left ventricle thicker than the wall of the right ventricle?
It receives blood directly from the venae cavae
It contracts well before the right ventricle
It ejects a larger volume per beat than the right
It pumps against much higher systemic pressure
✓
Correct Answer
It pumps against much higher systemic pressure
The left ventricle pushes blood into the high-pressure systemic circulation, while the right ventricle pumps into the low-pressure pulmonary circuit, so the left needs more muscle. The venae cavae empty into the right atrium, not the left ventricle. The two ventricles contract nearly at the same time. Over time both ventricles eject about the same volume, or blood would pool in one circuit.
Category: Heart Anatomy
Question 5
What is the "atrial kick" in the cardiac cycle?
Atrial contraction that tops off ventricular filling
✓
Recoil of the aorta after ventricular ejection
Closure of the valves at the start of systole
Spontaneous firing of the pacemaker at rest
Correct Answer
Atrial contraction that tops off ventricular filling
Near the end of ventricular diastole, the atria contract and push a final volume of blood into the ventricles, which is the atrial kick. Recoil of the aorta after ejection helps keep blood moving but is not the atrial kick. Closure of the valves at the start of systole produces a heart sound, not extra filling. Spontaneous firing of the pacemaker starts each beat but is an electrical event.
Category: Cardiac Output
Question 6
A patient has a heart rate of 80 beats per minute and a stroke volume of 70 mL. What is the cardiac output in liters per minute?
0.15 L/min
5.6 L/min
✓
56 L/min
1.1 L/min
Correct Answer
5.6 L/min
Cardiac output equals heart rate times stroke volume: 80 beats/min x 70 mL = 5,600 mL/min, which is 5.6 L/min. The value 0.15 L/min comes from adding 80 and 70 instead of multiplying. The value 56 L/min is a decimal error when converting milliliters to liters. The value 1.1 L/min comes from dividing heart rate by stroke volume.
Category: Cardiac Output
Question 7
By definition, a drug with a positive inotropic effect increases which property of the heart?
Heart rate
Speed of AV node conduction
Force of ventricular contraction
✓
Systemic vascular resistance
Correct Answer
Force of ventricular contraction
Inotropic effects change contractility, the strength of each contraction, which raises stroke volume. Changes in heart rate are chronotropic effects. Changes in conduction speed through the AV node are dromotropic effects. Systemic vascular resistance depends on blood vessel tone, which affects afterload rather than contractility.
Category: Cardiac Output
Question 8
A patient's blood pressure is 120/80 mm Hg. Using MAP = (2 x diastolic + systolic) / 3, what is the mean arterial pressure, rounded to the nearest whole number?
100 mm Hg
107 mm Hg
40 mm Hg
93 mm Hg
✓
Correct Answer
93 mm Hg
MAP = (2 x 80 + 120) / 3 = 280 / 3 = 93.3, which rounds to 93 mm Hg. Diastole is weighted double because the heart spends more of each cycle relaxing. The value 100 mm Hg is a simple average of the two numbers. The value 107 mm Hg comes from doubling the systolic instead of the diastolic pressure. The value 40 mm Hg is the pulse pressure, systolic minus diastolic.
Category: Blood Pressure Regulation
Question 9
Which substance in the hormonal pressure-regulating cascade is a potent vasoconstrictor that also stimulates release of aldosterone and antidiuretic hormone?
Angiotensin II
✓
Angiotensin I
Renin
Bradykinin
Correct Answer
Angiotensin II
Angiotensin II constricts arterioles, promotes sodium and water retention, and triggers aldosterone and ADH release, all of which raise blood pressure; ACE inhibitors and ARBs target this step. Angiotensin I is a largely inactive precursor. Renin is the kidney enzyme that starts the cascade by forming angiotensin I. Bradykinin is a vasodilator, not a vasoconstrictor.
Category: Blood Pressure Regulation
Question 10
In a cardiac muscle cell, which protein, once bound by the ion released from the sarcoplasmic reticulum, shifts tropomyosin aside so actin and myosin can interact?
Myoglobin
Troponin
✓
Titin
Calmodulin
Correct Answer
Troponin
When calcium binds troponin, the troponin-tropomyosin complex moves off the binding sites on actin, so myosin can attach and the cell contracts. Myoglobin stores oxygen in muscle. Titin is a large elastic protein that gives the sarcomere its stretch and recoil. Calmodulin is the calcium-binding protein that controls contraction in smooth muscle, not cardiac muscle.
Category: Cardiac Action Potential
Question 11
Which hormone, also given as a drug in septic shock, raises blood volume by making the kidney's collecting ducts more permeable to water?
Aldosterone
Epinephrine
Vasopressin
✓
Renin
Correct Answer
Vasopressin
Vasopressin, also called antidiuretic hormone, is released when blood pressure falls and increases water reabsorption in the collecting ducts; at higher levels it also constricts blood vessels. Aldosterone acts mainly by increasing sodium reabsorption and potassium excretion. Epinephrine is used in shock but acts on adrenergic receptors, not collecting duct water channels. Renin is an enzyme that starts the angiotensin cascade.
Category: Blood Pressure Regulation
Question 12
When a person stands up quickly and blood pressure drops, the baroreceptor reflex produces which response?
Baroreceptors sense the fall in pressure and quickly raise sympathetic activity, which constricts vessels and speeds the heart to restore pressure. Increased vagal output that slows the heart would lower pressure further. Decreased renin release would reduce angiotensin II when more is needed. Reduced antidiuretic hormone release would lose water when the body needs to hold it.
Category: Blood Pressure Regulation
Question 13
Why does the sinoatrial node normally set the heart rate?
It reaches threshold faster than other pacemaker cells
✓
It is the only tissue with automaticity
It lies in the wall of the left ventricle
It receives no autonomic nerve input
Correct Answer
It reaches threshold faster than other pacemaker cells
The sinoatrial node fires spontaneously at a faster rate than the AV node, bundle of His or Purkinje fibers, so it captures the heart and suppresses the slower sites. Other conduction tissues also have automaticity and can take over if it fails. It lies in the right atrium, not the left ventricle. It receives both sympathetic and parasympathetic input, which speed or slow its rate.
Category: Conduction System
Question 14
What does the brief delay of the impulse at the atrioventricular node allow?
The ventricles to repolarize before the atria contract
The atria to empty into the ventricles before they contract
✓
The pacemaker to recharge before firing again
The coronary arteries to fill during atrial systole
Correct Answer
The atria to empty into the ventricles before they contract
Slowing the impulse at the atrioventricular node gives the atria time to finish contracting and fill the ventricles before ventricular systole begins. The ventricles repolarize later, after they contract. The pacemaker cells recharge through their own spontaneous current, not because of this delay. Filling of the coronary arteries is not the purpose of the delay.
Category: Conduction System
Question 15
After leaving the bundle of His, the electrical impulse travels next through which structures?
Purkinje fibers
Internodal pathways
Right and left bundle branches
✓
Sinoatrial node
Correct Answer
Right and left bundle branches
The bundle of His divides into the right and left bundle branches, which run down the septum. Purkinje fibers come after the bundle branches and spread the impulse through the ventricular muscle. Internodal pathways carry the impulse through the atria before it reaches the AV node. The sinoatrial node is where the impulse begins.
Category: Conduction System
Question 16
Influx of which ion through L-type channels sustains the plateau phase of the cardiac muscle action potential?
Sodium
Chloride
Magnesium
Calcium
✓
Correct Answer
Calcium
During the plateau, calcium enters through L-type channels while potassium leaves, keeping the cell depolarized long enough for contraction; calcium channel blockers act on these channels. Sodium influx causes the rapid upstroke of depolarization, not the plateau. Chloride is not the main ion of the cardiac plateau. Magnesium does not carry the plateau current.
Category: Cardiac Action Potential
Question 17
Why can a cardiac muscle cell not be depolarized again immediately after it depolarizes?
Its sodium channels are temporarily inactive
✓
Its calcium stores are permanently depleted
Its gap junctions close after each beat
Its potassium channels are blocked by acetylcholine
Correct Answer
Its sodium channels are temporarily inactive
During the refractory period, the sodium channels that produced depolarization are inactivated and cannot reopen until the cell repolarizes, which prevents sustained contraction. The calcium stores are refilled after every beat, not permanently depleted. Gap junctions stay open to let current pass between cells. Acetylcholine does not block potassium channels to cause the refractory period.
Category: Cardiac Action Potential
Question 18
On an ECG, ventricular repolarization appears as which waveform?
P wave
T wave
✓
QRS complex
U wave
Correct Answer
T wave
The T wave records ventricular repolarization, the recovery of the ventricles before the next beat. The P wave records atrial depolarization. The QRS complex records ventricular depolarization. A U wave, when present, is a small wave after the T wave and is not the main sign of ventricular repolarization.
Category: ECG Basics
Question 19
How is the QT interval measured on an ECG?
From the start of the P wave to the start of the QRS complex
From the end of the QRS complex to the start of the T wave
From the start of the QRS complex to the end of the T wave
✓
From one R wave to the next R wave
Correct Answer
From the start of the QRS complex to the end of the T wave
The QT interval spans ventricular depolarization and repolarization, from the start of the QRS complex to the end of the T wave; many drugs can prolong it and raise the risk of torsades de pointes. From the start of the P wave to the start of the QRS complex is the PR interval. From the end of the QRS complex to the start of the T wave is the ST segment. From one R wave to the next is the R-R interval, used to find heart rate.
Category: ECG Basics
Question 20
Which change in the blood vessels increases systemic vascular resistance and so raises blood pressure?
Widening of the arterioles
Dilation of the large veins
Thinning of the capillary walls
Narrowing of the arterioles
✓
Correct Answer
Narrowing of the arterioles
Resistance depends on vessel diameter, and the arterioles are a major site of control, so constricting them raises systemic vascular resistance and blood pressure. Widening of the arterioles lowers resistance, which is how arterial vasodilators reduce pressure. Dilation of the large veins pools blood and reduces return to the heart rather than raising resistance. Thinning of the capillary walls affects exchange with tissues, not resistance.
Category: Blood Pressure Regulation