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Cardiovascular & Respiratory Systems
The heart and lungs work as one delivery system for oxygen and removal of carbon dioxide. You will follow blood through the heart, read pressure curves, connect flow to resistance, and predict how the oxygen-hemoglobin curve and breathing respond to physiology.
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What this chapter covers
- Heart Anatomy & the Cardiac Cycle. Valve timing and pressure curves are favorite exam material. Know which valves are open at each point in the cycle.
- Cardiac Output, Blood Pressure & Vessels. Pressure, flow, and resistance link every cardiovascular question. Poiseuille's r⁴ rule and the baroreflex show up often.
- Blood Components. Know what each cell type does, how the clotting cascade ends, and how ABO and Rh compatibility works.
- Gas Exchange & the Oxygen-Hemoglobin Curve. Expect the dissociation curve on nearly every MCAT. Know what shifts it, in which direction, and why the shift matters.
- Breathing Mechanics & Control. Pressure changes drive airflow, volumes come from a spirometer trace, and the brainstem controls breathing mostly through CO₂.
Key points to know
- SA node sets the pace; the AV node adds a 0.1 s delay
- Isovolumetric phases have all four valves closed
- CO = HR × SV; Frank-Starling: more stretch, more force
- MAP = CO × TPR
- Mature RBCs have no nucleus or mitochondria and rely on glycolysis
- Thrombin converts fibrinogen to fibrin; plasmin dissolves clots
- P50 ≈ 26 mmHg; right shift = higher P50 = easier unloading
- Right shift: ↑CO₂, ↑H⁺, ↑temperature, ↑2,3-BPG
Try a practice question
Which valve prevents blood from flowing back from the left ventricle into the left atrium?
- Tricuspid valve
- Mitral (bicuspid) valve
- Pulmonic valve
- Aortic valve
Show the answer
B. The mitral valve sits between the left atrium and left ventricle. The tricuspid is its right-sided counterpart, and the aortic and pulmonic valves guard the exits of the ventricles.
Common questions
What does this chapter cover?
Cardiovascular & Respiratory Systems covers Heart Anatomy & the Cardiac Cycle, Cardiac Output, Blood Pressure & Vessels, Blood Components, Gas Exchange & the Oxygen-Hemoglobin Curve, Breathing Mechanics & Control.
What should I know first?
SA node sets the pace; the AV node adds a 0.1 s delay Isovolumetric phases have all four valves closed CO = HR × SV; Frank-Starling: more stretch, more force
24 original practice questions accompany this chapter in the app. Spaced review brings missed ideas back at the right time; it helps memory but cannot promise you will not miss an idea again.