Quiz · Medium
Blood flow through the heart, valves, the conduction system, ECG waves and cardiac output calculations. Built for A&P 1–2 and pre-nursing students.
Deoxygenated blood returning from the body first enters which chamber?
Left atrium
Right ventricle
Left ventricle
Right atrium
The superior and inferior venae cavae empty into the right atrium. The left atrium receives oxygenated blood from the lungs through the pulmonary veins.
Which sequence is the correct path of blood through the right side of the heart?
Right atrium → mitral valve → right ventricle → aortic valve → aorta
Right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary trunk
Right ventricle → tricuspid valve → right atrium → pulmonary veins
Right atrium → pulmonary valve → right ventricle → tricuspid valve → lungs
Blood passes an AV valve (tricuspid on the right) between atrium and ventricle, then a semilunar valve (pulmonary) on the way out. The mitral and aortic valves are on the left side.
Which vessels carry oxygen-rich blood?
Pulmonary arteries
Venae cavae
Pulmonary veins
The coronary sinus
Arteries carry blood away from the heart and veins carry it toward the heart, whatever its oxygen level. The pulmonary veins bring oxygenated blood from the lungs to the left atrium; the pulmonary arteries carry deoxygenated blood to the lungs.
Which valve sits between the left atrium and the left ventricle?
Mitral (bicuspid) valve
Tricuspid valve
Aortic valve
Pulmonary valve
The mitral valve has two cusps and is the left AV valve. Memory aid: tri before you bi, meaning the tricuspid is on the right side, which blood reaches first.
Which chamber has the thickest muscular wall, and why?
Right ventricle, because it pumps blood to the lungs
Left atrium, because it receives blood from the lungs
Left ventricle, because it pumps blood through the whole systemic circulation
Right atrium, because it receives blood from the whole body
The left ventricle must generate much higher pressure (about 120 mmHg systolic) than the right ventricle, which only pushes blood through the short, low-resistance pulmonary circuit.
What is the correct order of the cardiac conduction system?
AV node → SA node → bundle of His → Purkinje fibers → bundle branches
SA node → bundle of His → AV node → Purkinje fibers → bundle branches
Purkinje fibers → bundle branches → bundle of His → AV node → SA node
SA node → AV node → bundle of His → bundle branches → Purkinje fibers
The SA node in the right atrium is the natural pacemaker. The impulse is delayed at the AV node, then races down the bundle of His and bundle branches to the Purkinje fibers in the ventricular walls.
Why does the AV node delay the electrical impulse by about 0.1 second?
To let the SA node recharge
To stop the ventricles from ever contracting
To allow the valves to open during systole
To let the atria finish emptying into the ventricles before the ventricles contract
The delay keeps atrial and ventricular contraction in sequence so the ventricles fill fully. On an ECG this delay is part of the PR interval.
A patient's heart rate is 70 beats/min and stroke volume is 70 mL/beat. What is the cardiac output?
4.9 L/min
140 mL/min
1.0 L/min
49 L/min
Cardiac output = heart rate × stroke volume = 70 × 70 mL = 4,900 mL/min = 4.9 L/min, close to the typical resting value of about 5 L/min. Adding the numbers (140) is a common slip.
End-diastolic volume is 120 mL and end-systolic volume is 50 mL. What is the ejection fraction?
About 42%
About 58%
70%
About 240%
Stroke volume = EDV − ESV = 120 − 50 = 70 mL. Ejection fraction = SV / EDV = 70 / 120 ≈ 0.58, or 58%, within the normal range of about 55–70%. 42% would be ESV / EDV.
On an ECG, the QRS complex represents:
Atrial depolarization
Ventricular depolarization
Ventricular repolarization
Atrial repolarization only
P wave = atrial depolarization, QRS complex = ventricular depolarization, T wave = ventricular repolarization. Atrial repolarization happens at the same time as the QRS and is hidden by it.
The first heart sound (S1, the lub) is caused by:
Closure of the aortic and pulmonary valves
Closure of the AV (mitral and tricuspid) valves
Opening of the AV valves
Blood hitting the walls of the aorta
S1 marks the start of ventricular systole, when rising ventricular pressure snaps the AV valves shut. S2 (dub) is the closure of the semilunar valves at the start of diastole.
A patient's blood pressure is 120/80 mmHg. What is the approximate mean arterial pressure (MAP)?
100 mmHg
80 mmHg
93 mmHg
40 mmHg
MAP ≈ diastolic + 1/3 (systolic − diastolic) = 80 + 1/3 (40) ≈ 93 mmHg. It is not the simple average (100) because the heart spends about two-thirds of each cycle in diastole.
Gas and nutrient exchange between blood and tissues happens across which vessels?
Arterioles
Capillaries
Venules
Elastic arteries
Capillary walls are a single layer of endothelial cells, thin enough for diffusion. Arterioles mainly control resistance and blood flow into capillary beds.
Which features help return blood from the legs to the heart against gravity?
Thick muscular walls in the veins
High blood pressure in the veins
Valves in the arteries of the legs
One-way valves in veins plus the squeezing of skeletal muscles
Veins have thin walls and low pressure, so they depend on valves and the skeletal muscle pump (plus breathing movements). Valve failure leads to varicose veins.
Which arteries are the first branches of the aorta, and what do they supply?
The coronary arteries, which supply the heart muscle
The carotid arteries, which supply the brain
The pulmonary arteries, which supply the lungs
The renal arteries, which supply the kidneys
The left and right coronary arteries branch from the base of the aorta just above the aortic valve. A blockage in them causes a myocardial infarction (heart attack).
According to the Frank-Starling law, if venous return increases, then:
Heart rate decreases to compensate
Stroke volume increases because the stretched ventricle contracts more forcefully
Stroke volume decreases because the ventricle is overfilled
The SA node stops firing
More filling stretches the cardiac muscle fibers toward their optimal length, so they contract harder. This keeps the output of the two ventricles matched beat by beat.
Which change shifts the oxygen-hemoglobin dissociation curve to the right (the Bohr effect), so more O₂ is released to tissues?
Lower temperature
Higher pH
Lower CO₂
Higher CO₂ and lower pH, as in active muscle
Active tissue is warmer, more acidic and higher in CO₂ (and 2,3-BPG), and each of these lowers hemoglobin's affinity for oxygen. Cold, alkaline conditions shift the curve to the left.
In fetal circulation, the foramen ovale allows blood to:
Pass from the right atrium to the left atrium, bypassing the lungs
Pass from the pulmonary trunk to the aorta
Flow from the placenta to the liver
Move from the left ventricle to the right ventricle
Fetal lungs are not used for gas exchange, so blood skips them through the foramen ovale (between the atria) and the ductus arteriosus (pulmonary trunk to aorta). Both normally close after birth.
Baroreceptors in the carotid sinus detect a sudden drop in blood pressure. What is the response?
More parasympathetic activity: slower heart rate
Vasodilation of arterioles throughout the body
Lower cardiac output to protect the heart
More sympathetic activity: faster heart rate and vasoconstriction
The baroreceptor reflex is negative feedback. Low pressure means fewer baroreceptor signals, so the brainstem raises sympathetic output to increase heart rate, contractility and vascular resistance and bring pressure back up.
