Chapter 7: The Cardiovascular System
🎯 Diagnostic: Test Your Starting Level 24 questions (~2 per section). No prior reading required, see what you already know.
Aim to answer every question before checking. Missed questions point you to the sections you need most.
1. (7.1) The right side of the heart receives:
B. The right heart is the pulmonary pump: venous blood in via SVC/IVC, then out the pulmonary artery to the lungs. The left heart is the systemic pump.
2. (7.1) The mitral (bicuspid) valve sits between:
D. Mitral = left AV valve (2 cusps). Tricuspid = right AV valve (3 cusps). Aortic and pulmonic are semilunar valves at the outflow tracts.
3. (7.2) During ventricular systole:
A. Ventricular contraction raises pressure; AV valves slam shut (S1 "lub"), then semilunars pop open and blood ejects.
4. (7.2) The S2 ("dub") heart sound corresponds to:
C. S1 = AV valves shut at the start of systole. S2 = semilunar valves shut at the start of diastole.
5. (7.3) The pacemaker of the heart is the:
D. The SA node fires at the highest intrinsic rate (~70-80 bpm) and sets the sinus rhythm. If it fails, the AV node (40-60 bpm) or ventricular pacemakers (20-40 bpm) take over.
6. (7.3) The AV node delays conduction to:
B. The ~0.1 s AV delay prevents simultaneous atrial/ventricular contraction and maximizes ventricular filling.
7. (7.4) The QRS complex on an ECG represents:
C. QRS reflects the rapid ventricular depolarization. Atrial repolarization is buried inside the QRS. T wave = ventricular repolarization.
8. (7.4) The P wave on an ECG represents:
A. The P wave is the small bump before QRS, produced as the wave spreads across the atria from the SA node.
9. (7.5) Cardiac output equals:
D. CO = SV × HR. A typical resting value is about 5 L/min (70 mL × 70 bpm). Exercise can raise CO to 20+ L/min.
10. (7.5) The Frank-Starling law states that:
B. More preload stretches sarcomeres toward their optimal length, yielding stronger contraction. This helps match output of the right and left ventricles beat-to-beat.
11. (7.6) The baroreceptor reflex responds to a sudden drop in blood pressure by:
A. Carotid/aortic baroreceptors detect reduced stretch; fewer inhibitory signals reach the medulla, sympathetic outflow rises, and BP is restored.
12. (7.6) The renin-angiotensin-aldosterone system (RAAS) responds to low blood pressure by ultimately:
C. Renin from the JG apparatus cleaves angiotensinogen to ANG I; ACE converts it to ANG II, which vasoconstricts and triggers aldosterone (Na⁺/water retention) and ADH.
13. (7.7) Arteries, compared with veins:
B. Arteries withstand high pulsatile pressure with thick tunica media (smooth muscle + elastin). Veins are low-pressure reservoirs with thinner walls and valves. The pulmonary artery is an arterial exception: it carries deoxygenated blood.
14. (7.7) Elastic recoil of the aorta during diastole is important because it:
A. The aorta acts as a pressure reservoir (Windkessel effect). Its elastin stores energy during systole and releases it in diastole, maintaining continuous perfusion.
15. (7.8) Net fluid exchange at capillaries is governed by:
D. Filtration out at the arterial end (hydrostatic wins); reabsorption at the venous end (oncotic wins). Net leftover fluid is cleared by lymphatics.
16. (7.8) Capillaries exchange materials with tissues primarily through:
C. Thin endothelium plus short distances make diffusion highly effective. Fenestrated and sinusoidal capillaries also allow bulk flow of fluid and some macromolecules.
17. (7.9) Mature erythrocytes (red blood cells) lack:
A. Mature RBCs extrude their nucleus and organelles to maximize hemoglobin content. They rely on anaerobic glycolysis and live about 120 days.
18. (7.9) Platelets are:
D. Megakaryocytes in the bone marrow shed cytoplasmic fragments that become platelets. Thrombopoietin regulates their production.
19. (7.10) The coagulation cascade ultimately produces:
B. Thrombin cleaves fibrinogen to fibrin monomers, which polymerize; Factor XIIIa crosslinks them into a stable mesh that traps platelets and RBCs.
20. (7.10) Vitamin K is required for:
C. Without vitamin-K-dependent γ-carboxylation, these factors cannot bind Ca²⁺ and assemble on membranes. Warfarin blocks vitamin K recycling, producing anticoagulation.
21. (7.11) The lymphatic system functions to:
D. Lymph capillaries pick up excess interstitial filtrate (plus fats via lacteals). Lymph nodes screen the fluid for pathogens using lymphocytes.
22. (7.11) Lymph ultimately empties into:
A. Lymph rejoins venous blood at the junction of the internal jugular and subclavian veins, closing the fluid loop.
23. (7.5) Ejection fraction is calculated as:
C. Normal EF is about 55-70%. Low EF (<40%) is a hallmark of systolic heart failure.
24. (7.1) The pulmonary artery carries:
B. The pulmonary artery is the only artery that carries deoxygenated blood. The pulmonary veins are the only veins that carry oxygenated blood.
You are standing in the kitchen when a spider drops from the ceiling onto your arm. Before you even identify what it is, your heart is already pounding. You did not decide to increase your heart rate. You did not consciously redirect blood flow to your muscles. Your cardiovascular system made that call on its own - within a single heartbeat.
Your heart beats roughly 100,000 times a day, pumping about 7,500 liters of blood through a network of vessels that, laid end to end, would circle the Earth more than twice. Every organ in your body depends on this continuous delivery service. Stop it for five minutes, and brain cells start dying. And yet, most of the time, you never think about it at all.
The cardiovascular system is one of the most heavily tested systems on the MCAT - and for good reason. It sits at the intersection of anatomy, physiology, physics (fluid dynamics, pressure gradients), and biochemistry (gas exchange, hemoglobin binding). If you understand how the heart pumps, how blood flows, and how the body regulates pressure, you can reason through almost any cardiovascular passage the MCAT throws at you.
In This Chapter
- 7.1 Heart Anatomy
- 7.2 The Cardiac Cycle
- 7.3 Cardiac Conduction System
- 7.4 Electrocardiogram (ECG) Basics
- 7.5 Cardiac Output, Stroke Volume, and Heart Rate
- 7.6 Blood Pressure and Its Regulation
- 7.7 Blood Vessel Types
- 7.8 Capillary Exchange and Starling Forces
- 7.9 Blood Composition
- 7.10 Coagulation Cascade
- 7.11 Lymphatic System Overview
- Section Test