ACSM-EP Cardiovascular Physiology 2 — Questions and Answers
Question 1: Which of the following best describes the Frank-Starling mechanism?
- Increased heart rate leads to increased stroke volume
- Greater ventricular end-diastolic volume results in a stronger contraction (Correct answer)
- Sympathetic stimulation decreases myocardial contractility
- Afterload reduction directly increases preload
Correct answer: Greater ventricular end-diastolic volume results in a stronger contraction
The Frank-Starling mechanism states that as ventricular filling (preload) increases, the force of contraction increases due to greater actin-myosin cross-bridge formation.
Question 2: During maximal aerobic exercise, which factor contributes MOST to the increase in cardiac output in trained individuals?
- Elevated resting heart rate
- Increased stroke volume due to enhanced ventricular filling and ejection (Correct answer)
- Reduced total peripheral resistance only
- Elevated diastolic blood pressure
Correct answer: Increased stroke volume due to enhanced ventricular filling and ejection
Trained individuals achieve higher cardiac output primarily through a larger stroke volume (augmented preload via plasma volume expansion and enhanced ejection fraction) rather than heart rate alone.
Question 3: What is the primary determinant of diastolic blood pressure?
- Stroke volume
- Heart rate
- Total peripheral resistance (Correct answer)
- Venous return
Correct answer: Total peripheral resistance
Diastolic blood pressure is primarily determined by total peripheral resistance, which reflects the degree of vasoconstriction in arterioles.
Question 4: A 45-year-old client has a resting cardiac output of 5 L/min and a heart rate of 70 bpm. What is the stroke volume?
- 50 mL
- 71 mL (Correct answer)
- 85 mL
- 100 mL
Correct answer: 71 mL
Stroke volume = Cardiac output / Heart rate = 5000 mL / 70 bpm ≈ 71 mL.
Question 5: Which physiological change explains the redistribution of blood flow to active muscles during exercise?
- Generalized vasoconstriction throughout the body
- Local metabolic vasodilation in active muscles with vasoconstriction in non-essential beds (Correct answer)
- Decreased cardiac output to the viscera
- Increased venous pressure in active limbs
Correct answer: Local metabolic vasodilation in active muscles with vasoconstriction in non-essential beds
Local metabolites (CO₂, lactate, adenosine, K⁺) cause vasodilation in active muscles, while sympathetic vasoconstriction reduces flow to splanchnic and renal beds.
Question 6: Which ECG change is a normal physiological response to aerobic endurance training?
- Prolonged QRS duration
- Resting sinus bradycardia (Correct answer)
- ST-segment depression at rest
- Increased P-wave amplitude
Correct answer: Resting sinus bradycardia
Endurance training increases vagal tone, lowering resting heart rate and producing sinus bradycardia, which is a normal adaptation.
Question 7: The oxygen pulse during a graded exercise test is calculated as VO₂ divided by heart rate. What does a plateau in oxygen pulse indicate?
- Maximal ventilatory capacity has been reached
- Stroke volume has plateaued and further VO₂ increases are heart-rate dependent (Correct answer)
- The subject has reached the ventilatory threshold
- Peripheral oxygen extraction has decreased
Correct answer: Stroke volume has plateaued and further VO₂ increases are heart-rate dependent
Oxygen pulse (VO₂/HR) is a surrogate for stroke volume × oxygen extraction; a plateau suggests stroke volume is no longer rising despite increasing workload.
ACSM-EP Cardiovascular Physiology 2
Which of the following best describes the Frank-Starling mechanism?