CCI Cardiac Anatomy and Physiology 5 — Questions and Answers
Question 1: Which cardiac structure is the primary determinant of afterload for the left ventricle?
- Pulmonary vascular resistance
- Left atrial pressure
- Systemic vascular resistance (Correct answer)
- Venous return volume
Correct answer: Systemic vascular resistance
Left ventricular afterload is primarily determined by systemic vascular resistance (SVR), which the LV must overcome to eject blood into the aorta.
Question 2: In a normal adult heart, the QRS complex duration should not exceed:
- 80 ms (0.08 sec)
- 120 ms (0.12 sec) (Correct answer)
- 160 ms (0.16 sec)
- 200 ms (0.20 sec)
Correct answer: 120 ms (0.12 sec)
Normal QRS duration is 60–100 ms; a QRS ≥120 ms indicates abnormal ventricular conduction (bundle branch block or ventricular origin).
Question 3: Which portion of the cardiac conduction system has the slowest conduction velocity, creating the PR interval delay?
- Sinoatrial node
- Bundle of His
- Purkinje fibers
- Atrioventricular node (Correct answer)
Correct answer: Atrioventricular node
The AV node conducts at only 0.02–0.05 m/s, the slowest of any conduction tissue, creating a physiological delay that allows atrial emptying before ventricular contraction.
Question 4: The term 'preload' in cardiac physiology is best equated with:
- Aortic diastolic pressure
- Ventricular wall tension during systole
- Left ventricular end-diastolic volume or pressure (Correct answer)
- Systemic vascular resistance
Correct answer: Left ventricular end-diastolic volume or pressure
Preload represents the degree of ventricular stretch at end-diastole, clinically approximated by end-diastolic volume (EDV) or filling pressure (EDP).
Question 5: Which of the following correctly describes the relationship between the parietal and visceral pericardium?
- The visceral pericardium is the outermost fibrous layer
- The pericardial cavity lies between the visceral and parietal layers (Correct answer)
- The parietal pericardium directly contacts the myocardium
- The visceral and parietal layers are fused at the cardiac apex
Correct answer: The pericardial cavity lies between the visceral and parietal layers
The pericardial cavity, containing 15–50 mL of serous fluid, is located between the inner visceral layer (epicardium) and the outer parietal pericardium.
Question 6: Ventricular compliance refers to:
- The rate of myocardial relaxation after systole
- The ventricle's ability to change volume in response to a change in pressure (Correct answer)
- The maximum pressure the ventricle can generate
- Stroke volume per unit of heart rate
Correct answer: The ventricle's ability to change volume in response to a change in pressure
Compliance (ΔV/ΔP) describes how easily the ventricle distends; a stiff (non-compliant) ventricle requires higher filling pressures to achieve the same end-diastolic volume.
Question 7: The Thebesian veins drain directly into which cardiac structures?
- Coronary sinus only
- All four cardiac chambers (Correct answer)
- Right atrium and right ventricle only
- Left ventricle and right ventricle only
Correct answer: All four cardiac chambers
Thebesian veins (venae cordis minimae) are small veins in the walls of all four chambers that drain a small amount of myocardial venous blood directly into the cardiac chambers.
CCI Cardiac Anatomy and Physiology 5
Which cardiac structure is the primary determinant of afterload for the left ventricle?