NEX Anatomy and Physiology: The Cardiovascular System 2 — Questions and Answers
Question 1: Which valve separates the left atrium from the left ventricle?
- Tricuspid valve
- Mitral (bicuspid) valve (Correct answer)
- Aortic valve
- Pulmonary valve
Correct answer: Mitral (bicuspid) valve
The mitral valve, also called the bicuspid valve, is positioned between the left atrium and left ventricle to prevent backflow of blood during ventricular contraction.
The heart contains four valves that regulate blood flow. The mitral valve (bicuspid valve) sits between the left atrium and left ventricle. It has two leaflets and opens to allow oxygenated blood from the lungs to flow into the left ventricle. During systole, it closes to prevent regurgitation back into the left atrium. The tricuspid valve is on the right side between the right atrium and ventricle. The aortic and pulmonary valves are semilunar valves at the exits of the ventricles.
Question 2: What is the normal resting cardiac output for an average adult?
- 2-3 liters per minute
- 5-6 liters per minute (Correct answer)
- 8-10 liters per minute
- 12-15 liters per minute
Correct answer: 5-6 liters per minute
Normal resting cardiac output is approximately 5-6 liters per minute, calculated as stroke volume multiplied by heart rate.
Cardiac output (CO) is the volume of blood pumped by the heart per minute, calculated as CO = Stroke Volume x Heart Rate. At rest, with a stroke volume of approximately 70 mL and a heart rate of about 75 bpm, the cardiac output is roughly 5.25 L/min. During exercise, cardiac output can increase to 20-25 L/min in healthy adults. This measurement is crucial in nursing for assessing cardiac function and detecting heart failure.
Question 3: The sinoatrial (SA) node is located in which chamber of the heart?
- Left atrium
- Right atrium (Correct answer)
- Left ventricle
- Right ventricle
Correct answer: Right atrium
The SA node, the heart's natural pacemaker, is located in the upper wall of the right atrium near the superior vena cava.
The sinoatrial (SA) node is a cluster of specialized cardiac cells located in the posterior wall of the right atrium, near the junction of the superior vena cava. It initiates the electrical impulse that triggers each heartbeat, generating 60-100 impulses per minute at rest. The signal travels through the atrial walls to the atrioventricular (AV) node, then through the Bundle of His, bundle branches, and Purkinje fibers to stimulate ventricular contraction. Dysfunction of the SA node can lead to arrhythmias requiring pacemaker intervention.
Question 4: Which blood vessel carries deoxygenated blood from the heart to the lungs?
- Aorta
- Pulmonary artery (Correct answer)
- Pulmonary vein
- Superior vena cava
Correct answer: Pulmonary artery
The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs for gas exchange, making it the only artery that carries deoxygenated blood.
The pulmonary artery is unique because it is the only artery in the body that carries deoxygenated blood. Blood flows from the right ventricle through the pulmonary valve into the pulmonary trunk, which divides into the left and right pulmonary arteries leading to each lung. In the pulmonary capillaries, carbon dioxide is exchanged for oxygen. Oxygenated blood then returns via the pulmonary veins to the left atrium. The aorta carries oxygenated blood from the left ventricle to the systemic circulation.
Question 5: What does an elevated troponin level in the blood most commonly indicate?
- Liver damage
- Myocardial injury (Correct answer)
- Kidney failure
- Pulmonary embolism
Correct answer: Myocardial injury
Elevated troponin levels are the most sensitive and specific biomarker for myocardial injury, commonly used to diagnose acute myocardial infarction.
Troponin (troponin I and troponin T) is a protein found in cardiac muscle cells that is released into the bloodstream when myocardial cells are damaged. It is the gold standard biomarker for diagnosing acute myocardial infarction (heart attack). Troponin levels begin rising 3-6 hours after myocardial injury, peak at 12-24 hours, and can remain elevated for 7-14 days. While primarily associated with heart attacks, elevated troponin can also occur in myocarditis, heart failure, and other conditions causing cardiac stress.
Question 6: During which phase of the cardiac cycle do the ventricles fill with blood?
- Systole
- Diastole (Correct answer)
- Isovolumetric contraction
- Ejection phase
Correct answer: Diastole
During diastole, the ventricles relax and fill with blood from the atria, preparing for the next contraction cycle.
The cardiac cycle consists of systole (contraction) and diastole (relaxation). During ventricular diastole, the ventricles relax and their pressure drops below atrial pressure, causing the AV valves (mitral and tricuspid) to open. Blood flows passively from the atria into the ventricles, accounting for about 80% of ventricular filling. Atrial contraction (atrial kick) contributes the remaining 20%. Diastole corresponds to the diastolic blood pressure reading. Adequate diastolic time is essential for coronary perfusion, as the coronary arteries primarily fill during diastole.
NEX Anatomy and Physiology: The Cardiovascular System 2
Which valve separates the left atrium from the left ventricle?