- What is the duration of a complete cardiac cycle in a healthy human heart at rest?
A) 0.5 seconds
B) 0.8 seconds
C) 1 second
D) 1.2 seconds
Answer: B) 0.8 seconds - Which phase of the cardiac cycle is longest?
A) Atrial systole
B) Ventricular systole
C) Ventricular diastole
D) Isovolumetric relaxation
Answer: C) Ventricular diastole - The closure of which valves causes the first heart sound (“lub”)?
A) Atrioventricular valves
B) Semilunar valves
C) Tricuspid valve only
D) Mitral valve only
Answer: A) Atrioventricular valves - The second heart sound (“dub”) is associated with the closure of which valves?
A) Atrioventricular valves
B) Semilunar valves
C) Tricuspid valve only
D) Pulmonary valve only
Answer: B) Semilunar valves - Which of the following occurs during ventricular systole?
A) Blood flows into the atria
B) Atrioventricular valves open
C) Semilunar valves open
D) Heart is in relaxation phase
Answer: C) Semilunar valves open - What is the function of the sinoatrial (SA) node in the cardiac cycle?
A) It acts as the pacemaker
B) It stimulates ventricular contraction
C) It closes the semilunar valves
D) It initiates diastole
Answer: A) It acts as the pacemaker - What is the phase of the cardiac cycle when all valves are closed and ventricular pressure increases?
A) Atrial systole
B) Ventricular systole
C) Isovolumetric contraction
D) Ventricular filling
Answer: C) Isovolumetric contraction - During which phase of the cardiac cycle does blood flow from the atria into the ventricles?
A) Atrial systole
B) Ventricular systole
C) Ventricular diastole
D) Isovolumetric relaxation
Answer: A) Atrial systole - Which ion is critical for cardiac muscle contraction?
A) Sodium
B) Calcium
C) Potassium
D) Chloride
Answer: B) Calcium - What is the role of the atrioventricular (AV) node?
A) Initiates the heartbeat
B) Delays the impulse to allow atrial contraction
C) Directly contracts the ventricles
D) Closes the AV valves
Answer: B) Delays the impulse to allow atrial contraction
- The P wave in an ECG corresponds to which event in the cardiac cycle?
A) Atrial depolarization
B) Ventricular depolarization
C) Ventricular repolarization
D) Atrial repolarization
Answer: A) Atrial depolarization - Which of the following events occurs last in the cardiac cycle?
A) Isovolumetric relaxation
B) Atrial systole
C) Ventricular systole
D) Ventricular diastole
Answer: D) Ventricular diastole - The T wave in an ECG indicates what event?
A) Atrial depolarization
B) Ventricular depolarization
C) Ventricular repolarization
D) Atrial systole
Answer: C) Ventricular repolarization - During the cardiac cycle, what happens to ventricular pressure during isovolumetric relaxation?
A) Increases
B) Decreases
C) Remains constant
D) Fluctuates
Answer: B) Decreases - Which phase is responsible for filling the coronary arteries with blood?
A) Atrial systole
B) Ventricular systole
C) Ventricular diastole
D) Isovolumetric contraction
Answer: C) Ventricular diastole
- The Frank-Starling law of the heart states that:
A) Greater preload increases stroke volume
B) Lower preload increases stroke volume
C) Heart rate determines stroke volume
D) Stroke volume is independent of preload
Answer: A) Greater preload increases stroke volume - What happens to the heart rate when the vagus nerve is stimulated?
A) Increases
B) Decreases
C) Remains constant
D) Becomes irregular
Answer: B) Decreases - Which neurotransmitter is released by the sympathetic nervous system to increase heart rate?
A) Acetylcholine
B) Dopamine
C) Norepinephrine
D) Serotonin
Answer: C) Norepinephrine - Cardiac output is the product of heart rate and:
A) Blood pressure
B) Stroke volume
C) Preload
D) Afterload
Answer: B) Stroke volume - What regulates the opening and closing of the heart valves?
A) Nerve impulses
B) Blood pressure changes
C) Muscle contraction
D) Hormonal signals
Answer: B) Blood pressure changes
- What effect does increased afterload have on the cardiac cycle?
A) Decreases cardiac output
B) Increases ventricular filling
C) Speeds up heart rate
D) Enhances stroke volume
Answer: A) Decreases cardiac output - Which component of the cardiac cycle ensures unidirectional blood flow?
A) Myocardium
B) Heart valves
C) Coronary arteries
D) Atria
Answer: B) Heart valves - What phase is skipped in rapid heartbeats (tachycardia)?
A) Atrial systole
B) Isovolumetric contraction
C) Ventricular diastole
D) Isovolumetric relaxation
Answer: C) Ventricular diastole - Which chamber of the heart generates the highest pressure during systole?
A) Right atrium
B) Right ventricle
C) Left atrium
D) Left ventricle
Answer: D) Left ventricle - The dicrotic notch in a pressure waveform represents:
A) Closure of AV valves
B) Opening of semilunar valves
C) Closure of semilunar valves
D) Isovolumetric contraction
Answer: C) Closure of semilunar valves
- Baroreceptors help regulate heart rate by:
A) Sensing oxygen levels
B) Detecting changes in blood pressure
C) Monitoring blood pH
D) Stimulating coronary circulation
Answer: B) Detecting changes in blood pressure - What part of the brain primarily regulates cardiac activity?
A) Cerebrum
B) Medulla oblongata
C) Hypothalamus
D) Cerebellum
Answer: B) Medulla oblongata - Atrial natriuretic peptide (ANP) decreases blood pressure by:
A) Increasing stroke volume
B) Reducing blood volume
C) Constricting blood vessels
D) Enhancing heart rate
Answer: B) Reducing blood volume - During exercise, the cardiac cycle changes mainly by:
A) Lengthening diastole
B) Shortening systole
C) Shortening diastole
D) Reducing stroke volume
Answer: C) Shortening diastole - Which factor directly increases stroke volume?
A) Increased heart rate
B) Increased preload
C) Increased afterload
D) Reduced contractility
Answer: B) Increased preload
