What is the Cardiovascular System?
The cardiovascular system is the network of the heart, blood vessels, and blood that transports oxygen, nutrients, hormones, and waste throughout the body. It runs two connected circuits — pulmonary and systemic — powered by the rhythmic pumping of the heart.
The cardiovascular system circulates blood using the heart as a pump, arteries carrying blood away from the heart, veins returning it, and capillaries exchanging gases and nutrients with tissues; its output is measured as cardiac output (CO = HR × SV).
- 1.Right atrium — Receives deoxygenated blood from the body via the vena cava.
- 2.Right ventricle — Pumps blood through the pulmonary valve into the pulmonary artery.
- 3.Lungs (pulmonary circuit) — Blood releases CO₂ and picks up O₂ in the alveolar capillaries.
- 4.Left atrium — Receives oxygenated blood from the pulmonary veins.
- 5.Left ventricle — Pumps oxygenated blood through the aortic valve into the aorta.
- 6.Body tissues (systemic circuit) — Capillary beds deliver O₂ and nutrients, collecting CO₂ and waste, returning via veins to the right atrium.
Try it: interactive calculator
Step-by-step worked examples
A resting adult has a heart rate of 70 bpm and a stroke volume of 70 mL. Find cardiac output.
CO = HR × SV CO = 70 × 70 = 4900 mL/min CO = 4900/1000 = 4.9 L/min
During exercise, heart rate rises to 150 bpm and stroke volume to 100 mL. What is the new cardiac output?
CO = HR × SV CO = 150 × 100 = 15000 mL/min CO = 15000/1000 = 15 L/min
A patient's cardiac output is 5.4 L/min at a heart rate of 90 bpm. Find the stroke volume.
CO = HR × SV → SV = CO/HR SV = 5400 mL / 90 = 60 mL/beat
Flashcards
Quick quiz
Q1.A person has HR = 80 bpm and SV = 65 mL. What is their cardiac output?
Q2.Which vessel carries deoxygenated blood away from the heart?
Q3.Which chamber pumps blood into the systemic circuit?
Q4.If heart rate increases but stroke volume stays constant, cardiac output will…
The full card deck, worked steps and AI-tutor support for “What is the Cardiovascular System?” are in Notek — study by hand before your exam.
Common mistakes
Thinking all arteries carry oxygenated blood. — Correct: The pulmonary artery carries deoxygenated blood to the lungs — the rule is about direction (away from heart), not oxygen content.
Confusing cardiac output with heart rate alone. — Correct: Cardiac output depends on both heart rate AND stroke volume: CO = HR × SV.
Assuming blood in systemic veins is always oxygenated. — Correct: Systemic veins carry deoxygenated blood back to the heart; only the pulmonary vein carries oxygenated blood.
Believing the heart has only one circuit. — Correct: It runs two circuits simultaneously: pulmonary (to the lungs) and systemic (to the body).
FAQ
What is the cardiovascular system?
It's the heart, blood vessels, and blood that together transport oxygen, nutrients, and waste through the pulmonary and systemic circuits.
What is the cardiac output formula?
CO = HR × SV — cardiac output equals heart rate multiplied by stroke volume, typically expressed in L/min.
What are examples of cardiovascular system function?
A resting heart pumping ~5 L/min, or cardiac output rising to 15-20 L/min during intense exercise.
How do you calculate cardiac output?
Multiply heart rate (beats/min) by stroke volume (mL/beat), then divide by 1000 to convert to L/min.