Cardiovascular Physiology

Question 1: Why is the sinoatrial node the normal pacemaker of the heart?

• Answer: C. It has a higher intrinsic rate of firing than other parts of the heart.

Question 2: Where is the normal conduction pathway located in the human heart?

• Answer: B. Sinoatrial node

Question 3: Which of the following channels is the largest during the early phase of ventricular depolarization?

• Answer: D. Ca+ conductance

Question 4: Where in the heart is the conduction velocity of the action potential the fastest?

• Answer: D. Purkinje fibers

Question 5: What causes the depolarization phase of the sinoatrial node cells?

• Answer: A. Increased Na+ influx into the cell

Question 6: Why can’t the heart undergo tetanic contractions?

• Answer: A. The refractory period is long.

Question 7: An electrocardiogram (ECG) is most useful in detecting abnormalities in which of the following?

• Answer: B. Heart rhythm

Question 8: An ECG is least effective in detecting abnormalities in which of the following?

• Answer: E. Coronary blood flow

Question 9: How is the P-R interval on an ECG measured?

• Answer: B. From the beginning of the P wave to the beginning of the QRS complex

Question 10: What is the normal duration of the P wave on an ECG?

• Answer: A. 0.08 – 0.11 seconds

Question 11: Which of the following is true about the P-R interval on an ECG?

• Answer: D. It reflects the time it takes for the impulse to travel from the atria to the ventricles

Question 12: What is the normal duration of the P-R interval?

• Answer: A. 0.12 – 0.20 seconds

Question 13: Which wave on the ECG represents ventricular repolarization?

• Answer: C. T wave

Question 14: Which of the following is the main determinant of preload?

• Answer: D. End-diastolic left ventricular volume

Question 15: Which of the following is the main determinant of afterload?

• Answer: B. Aortic pressure during ventricular ejection

Question 16: When does the aortic valve close?

• Answer: D. At the beginning of isovolumetric relaxation

Question 17: Which of the following is true about the rate of blood ejection from the ventricle during systole?

• Answer: A. It is highest in the first 1/3 of systole

Question 18: What triggers the closure of the atrioventricular valves?

• Answer: E. Pressure in the ventricle exceeds pressure in the atrium

Question 19: Does the second heart sound occur during which of the following phases?

• Answer: A. Isovolumetric contraction

Question 20: What occurs after the first heart sound and before the second heart sound?

• Answer: A. The period of ventricular ejection

Question 21: In an individual, the oxygen consumption is measured to be 700 mL/min, the pulmonary arterial oxygen content is 140 mL/L of blood, and the systemic arterial oxygen content is 210 mL/L of blood. What is the cardiac output?

• Answer: C. 10.0 L/min

Question 22: Which of the following can decrease the stroke volume?

• Answer: E. Decreased preload

Question 23: What will increase with increased parasympathetic stimulation?

• Answer: C. Acetylcholine release

Question 24: At rest, how many liters does a healthy male heart pump in a minute?

• Answer: C. 5 to 6

Question 25: Which of the following will increase during exercise?

• Answer: A. Cardiac output

Question 26: Increased stimulation of the vagus nerve will increase which of the following?

• Answer: D. Acetylcholine release

Question 27: Which of the following describes the effect of respiration on heart rate?

• Answer: B. Heart rate increases during inspiration and decreases during expiration

Question 28: What is the effect of the reflex initiated by receptors in the ventricle?

• Answer: A. Decreased heart rate and decreased peripheral resistance

Question 29: An increase in plasma epinephrine concentration will lead to which of the following?

• Answer: C. Increased cardiac output

Question 30: In a normal individual, stroke volume will increase under which of the following conditions?

• Answer: A. Increased sympathetic stimulation to the heart

Question 31: Which of the following is NOT a factor that determines blood flow?

• Answer: C. Blood pH

Question 32: If the resting diameter of a blood vessel is halved, how many times does the resistance to blood flow increase?

• Answer: E. 16

Question 33: Which of the following is blood viscosity dependent on?

• Answer: E. All of the above

Question 34: Which of the following characteristics of the vessel wall is LEAST important?

• Answer: E. Abundant nerve endings

Question 35: Which of the following will decrease the driving pressure (pressure gradient) across the arteries?

• Answer: C. Decreased blood volume

Question 36: All of the following will increase arterial blood pressure EXCEPT:

• Answer: D. Increased elasticity of the vessel wall

Question 37: Where does the exchange of nutrients and gases between the blood and tissues occur?

• Answer: D. Capillaries

Question 38: Where is the total cross-sectional area of blood vessels the largest?

• Answer: C. Capillaries

Question 39: Where is the greatest percentage of blood volume located?

• Answer: E. Venules and veins

Question 40: Which of the following is true about the phenomenon of autoregulation in the vascular system?

• Answer: A. When perfusion pressure increases, the vessels constrict, and vice versa

Question 41: Which of the following neuronal areas participate in the vasomotor reflex?

• Answer: E. All of the above

Question 42: What is the effect of the baroreceptor reflex?

• Answer: B. Decreased heart rate, vasodilation

Question 43: What is the effect of the chemoreceptor reflex?

• Answer: B. Vasoconstriction

Question 44: A decrease in carotid sinus pressure will lead to a decrease in which of the following?

• Answer: D. Inhibition of the cardioinhibitory center

Question 45: When baroreceptors are under-stimulated, all of the following will increase EXCEPT:

• Answer: E. Parasympathetic nerve activity

Question 46: Preload is increased primarily due to an increase in which of the following?

• Answer: B. Venous tone

Question 47: What generates the first heart sound?

• Answer: A. Closure of the atrioventricular valves

Question 48: Why is the left ventricle thicker than the right ventricle?

• Answer: D. The left ventricle pumps blood against a higher pressure

Question 49: What generates the second heart sound?

• Answer: D. Closure of the semilunar valves

Question 50: Stimulation of the heart muscle will only produce a response when?

• Answer: B. Stimulation reaches the threshold and occurs during the relative refractory period

Question 51: Which of the following is true about the ventricular contraction phase?

• Answer: C. It causes the closure of the atrioventricular valves and opening of the aortic valve

Question 52: Which chamber plays the dominant role in the cardiac cycle?

• Answer: D. The entire ventricle

Question 53: At the moment the second heart sound is heard, what is happening in the heart?

• Answer: B. The ventricle is relaxing, the atrium is relaxing

Question 54: At the moment the first heart sound is heard, what is happening in the heart?

• Answer: B. The atrium is relaxing, the ventricle is just starting to contract

Question 55: Which of the following characteristics is the heart muscle known for?

• Answer: E. Both A and B are correct

Question 56: What causes the closure of the mitral and tricuspid valves?

• Answer: D. The pressure difference between the atrium and ventricle

Question 57: During the cardiac cycle, the period from the beginning of the closure of the atrioventricular valve to the end of the closure of the semilunar valve corresponds to which phase?

• Answer: E. Both B and C are correct

Question 58: When does the closure of the aortic valve occur in the cardiac cycle?

• Answer: D. At the beginning of isovolumetric relaxation

Question 59: Where is the automaticity of the heart evident?

• Answer: E. The entire heart

Question 60: The fourth heart sound is caused by:

• Answer: C. Rapid ventricular filling

Question 61: Where does the heart receive its blood supply from?

• Answer: E. All of the above

Question 62: What is the conduction velocity of the action potential in ventricular muscle fibers?

• Answer: B. 0.3-1 m/s

Question 63: What is the conduction velocity of the action potential in the Purkinje system?

• Answer: C. 1.5-4 m/s

Question 64: What generates phase 4 of the sinoatrial node cell action potential?

• Answer: B. The decrease in potassium current out of the cell

Question 65: When do the L-type (long-lasting) calcium channels open in the cardiac muscle cell membrane?

• Answer: D. The plateau

Question 66: What does sympathetic stimulation cause the release of?

• Answer: E. Only C and D are incorrect

Question 67: What is the significance of the Frank-Starling law of the heart?

• Answer: C. It illustrates the intrinsic regulation of heart function

Question 68: Which of the following is true about arterial blood pressure?

• Answer: A. It is directly proportional to vascular resistance and cardiac output

Question 69: Which of the following is true about mean arterial pressure (MAP)?

• Answer: D. It is an average of blood pressure readings taken in the arteries to ensure proper perfusion

Question 70: What is the main mechanism of exchange across capillaries?

• Answer: D. Passive diffusion

Question 71: In a patient with a very fast heart rate, rubbing the carotid sinus area in the neck will slow the heart rate. Why?

• Answer: E. Increased pressure in the carotid sinus

Question 72: Opening of which ion channel underlies the repolarization phase of the ventricular muscle cell action potential?

• Answer: D. K+ channels

Question 73: Substances that regulate blood pressure by acting on blood vessels and also on renal tubular reabsorption are:

• Answer: C. Angiotensin II and aldosterone

Question 74: Frank-Starling law:

• Answer: C. Explains the intrinsic regulation of heart function

Question 75: Arterial blood pressure:

• Answer: A. Directly proportional to vascular resistance and cardiac output

Question 76: Arterial blood pressure tends to increase in overweight individuals because:

• Answer: C. Increased blood volume

Question 77: Regular exercise provides the following benefits:

• Answer: E. All of the above

Question 78: At rest, how many liters does a healthy male heart pump in a minute?

• Answer: C. 5 to 6

Question 79: Plasma colloid osmotic pressure:

• Answer: E. All of the above are incorrect

Question 80: What increases during exercise?

• Answer: A. Cardiac output

Question 81: The main factor in the intrinsic regulation of the arterial system is:

• Answer: A. Intraluminal pressure

Question 82: The mechanism of autoregulation in the vascular system is as follows:

• Answer: B. Increased perfusion pressure causes vessel constriction

Question 83: The notch on the arterial pressure waveform is caused by:

• Answer: C. Closure of the aortic valve

Question 84: Which of the following increases blood pressure?

• Answer: C. Inhibitors of NO synthase

Question 85: When carotid sinus pressure is increased:

• Answer: A. Vasoconstriction

Question 86: The baroreceptor reflex is mediated by which of the following nerves?

• Answer: B. IX and X

Question 87: The portion of the ECG that corresponds to atrial depolarization is:

• Answer: D. P wave

Question 88: How does the heart rate change during inspiration compared to before inspiration?

• Answer: D. Heart rate is faster at the beginning, slower later

Question 89: Under what conditions does the amount of blood pumped out by the heart with each beat normally increase?

• Answer: E. Increased sympathetic activity

Question 90: Which of the following causes vasoconstriction?

• Answer: D. Endothelin I

Question 91: In vascular regulation, when pressure receptors are stimulated, what effects are produced?

• Answer: A. Inhibition of vasoconstrictor regions

Question 92: The mechanism of ultrafiltration in capillaries is:

• Answer: E. 85% of the fluid filtered through the capillaries is reabsorbed back into the capillaries

Question 93: What blood vessel carries venous blood from the head and neck to the heart?

• Answer: E. Superior vena cava

Question 94: Where is the blood pressure the highest?

• Answer: A. Aortic arch

Question 95: In vascular regulation, autoregulation and myogenic regulation:

• Answer: C. This response is independent of endothelial cells

Question 96: All of the following increase arterial blood pressure EXCEPT:

• Answer: D. Increased elasticity of the vessel wall

Question 97: Changing the frequency of contractions affects the force generated by the heart muscle as follows:

• Answer: D. The force of contraction of an early systole is often weak because less calcium is released

Question 98: Chemical receptors are stimulated when blood pressure drops:

• Answer: D. Below 80 mmHg

Question 99: Preload is:

• Answer: B. The tension of the cardiac muscle fibers before contraction

Question 100: During the ejection phase, the pressure difference is smallest between which of the following?

• Answer: C. Left ventricle and aorta