[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Physiology](https://durgical.com/en/physiology/) › Cardiovascular # Cardiovascular The heart as a pump, the ECG, hemodynamics and how blood pressure is controlled. 55 pages ## Exam priority: high - [**Cardiac output and what sets it** Regulation · Cardiac output is how much blood the heart pumps each minute: beats per minute times the volume…](https://durgical.com/en/physiology/cardiac-output-and-what-sets-it/) - [**ECG basics: waves, intervals and leads** Measurement · The ECG records the heart's electrical activity from the skin; each wave shows a part of the…](https://durgical.com/en/physiology/ecg-basics-waves-intervals-and-leads/) - [**Heart sounds and where they come from** Mechanism · The 'lub-dub' you hear is the sound of heart valves snapping shut; extra sounds can mean the…](https://durgical.com/en/physiology/heart-sounds-and-where-they-come-from/) - [**How edema forms** Mechanism · Swelling appears when more fluid leaves the blood vessels than the lymph can carry back](https://durgical.com/en/physiology/how-edema-forms/) - [**Shock physiology** Mechanism · Shock is when the circulation cannot deliver enough oxygen to the organs; cells switch to…](https://durgical.com/en/physiology/shock-physiology/) - [**Starling forces at the capillary** Mechanism · Blood pressure pushes fluid out of capillaries and blood proteins pull it back in; the lymph…](https://durgical.com/en/physiology/starling-forces-at-the-capillary/) - [**Systolic, diastolic, mean and pulse pressure** Measurement · Blood pressure has a top number when the heart pushes, a bottom number when it rests, and an…](https://durgical.com/en/physiology/systolic-diastolic-mean-and-pulse-pressure/) - [**The baroreceptor reflex** Regulation · Pressure sensors in the neck and aorta tell the brain about blood pressure each second, and the…](https://durgical.com/en/physiology/the-baroreceptor-reflex/) - [**The cardiac conduction system** Concept · A wiring path carries each beat from the top of the heart to the bottom, with a short pause so…](https://durgical.com/en/physiology/the-cardiac-conduction-system/) - [**The cardiac cycle** Mechanism · One heartbeat is a fixed sequence: the heart fills, squeezes with closed valves, ejects…](https://durgical.com/en/physiology/the-cardiac-cycle/) - [**The Frank–Starling mechanism** Mechanism · The more the heart is filled, the harder it squeezes, so it pumps out whatever blood comes back…](https://durgical.com/en/physiology/the-frank-starling-mechanism/) - [**The renin–angiotensin–aldosterone system** Regulation · When blood pressure or salt falls, the kidney releases renin, starting a chain of hormones that…](https://durgical.com/en/physiology/the-renin-angiotensin-aldosterone-system/) - [**The SA node pacemaker potential** Mechanism · Cells in the sinus node slowly charge themselves up until they fire, which sets the heart rate…](https://durgical.com/en/physiology/the-sa-node-pacemaker-potential/) - [**The ventricular action potential** Mechanism · Each ventricular muscle cell fires a long electrical signal with a plateau, so the heart…](https://durgical.com/en/physiology/the-ventricular-action-potential/) - [**The ventricular pressure–volume loop** Measurement · Plotting the ventricle's pressure against its volume in one beat draws a loop whose shape shows…](https://durgical.com/en/physiology/the-ventricular-pressure-volume-loop/) ## Exam priority: medium - [**Blood pressure control on three time scales: seconds, minutes and days** Table to know · Nerves fix blood pressure in seconds, hormones and fluid shifts in minutes to hours, and the…](https://durgical.com/en/physiology/blood-pressure-control-on-three-time-scales-seconds-minutes-and-days/) - [**Bundle branch and fascicular blocks** Measurement · When one branch of the heart's wiring is cut, that side is reached slowly through muscle, so the…](https://durgical.com/en/physiology/bundle-branch-and-fascicular-blocks/) - [**Cardiac excitation–contraction coupling** Mechanism · How each beat's electrical signal becomes force: a small calcium influx triggers a much larger…](https://durgical.com/en/physiology/cardiac-excitation-contraction-coupling/) - [**Central venous pressure and the jugular pulse** Measurement · Central venous pressure is the pressure of blood entering the right heart; the internal jugular…](https://durgical.com/en/physiology/central-venous-pressure-and-the-jugular-pulse/) - [**Coronary circulation and myocardial ischemia** Concept · The heart feeds mostly in diastole and already extracts almost all its oxygen at rest: if it…](https://durgical.com/en/physiology/coronary-circulation-and-myocardial-ischemia/) - [**ECG leads: Einthoven's triangle, augmented and chest leads** Concept · Each ECG lead looks at the heart's electricity from one angle](https://durgical.com/en/physiology/ecg-leads-einthoven-s-triangle-augmented-and-chest-leads/) - [**Flow, pressure and resistance: Poiseuille and turbulent flow** Concept · Blood flows from high to low pressure; narrow vessels resist flow enormously, and fast…](https://durgical.com/en/physiology/flow-pressure-and-resistance-poiseuille-and-turbulent-flow/) - [**Heart failure over time: acute, compensated, decompensated and high-output failure on the curves** Mechanism · After the heart is damaged, nerves act at once and the kidneys add fluid over days](https://durgical.com/en/physiology/heart-failure-over-time-acute-compensated-decompensated-and-high-output-failure/) - [**Heart failure physiology** Mechanism · In heart failure the heart cannot pump enough at normal filling pressures; the body's rescue…](https://durgical.com/en/physiology/heart-failure-physiology/) - [**Hemorrhagic shock: compensation, vicious cycles and irreversibility** Mechanism · After bleeding, the body squeezes vessels and holds fluid](https://durgical.com/en/physiology/hemorrhagic-shock-compensation-vicious-cycles-and-irreversibility/) - [**How arrhythmias arise** Mechanism · Abnormal heart rhythms come from cells that fire on their own, beats that trigger extra beats…](https://durgical.com/en/physiology/how-arrhythmias-arise/) - [**How ECG waves are built: the vectors of the QRS, T and P** Mechanism · At each instant the heart's current has one main direction and size, an arrow](https://durgical.com/en/physiology/how-ecg-waves-are-built-the-vectors-of-the-qrs-t-and-p/) - [**How the circulation adapts to valve disease: aortic and mitral lesions at rest and in exercise** Mechanism · A narrow or leaky valve makes the heart work harder](https://durgical.com/en/physiology/how-the-circulation-adapts-to-valve-disease-aortic-and-mitral-lesions-at-rest-an/) - [**Local and humoral control of blood flow** Regulation · Each tissue adjusts its own arterioles to get the blood it needs, even when arterial pressure…](https://durgical.com/en/physiology/local-and-humoral-control-of-blood-flow/) - [**Long-term blood pressure control by the kidney** Regulation · In the long run, blood pressure is set by the kidneys: if pressure rises, they excrete more salt…](https://durgical.com/en/physiology/long-term-blood-pressure-control-by-the-kidney/) - [**Measuring cardiac output: Fick, indicator and thermodilution, Doppler** Measurement · Cardiac output is measured from how much oxygen the body takes up, how fast an injected marker…](https://durgical.com/en/physiology/measuring-cardiac-output-fick-indicator-and-thermodilution-doppler/) - [**Murmurs and the hemodynamics of valve disease** Mechanism · A murmur is the sound of blood flowing turbulently through a narrow valve, a valve that does not…](https://durgical.com/en/physiology/murmurs-and-the-hemodynamics-of-valve-disease/) - [**Muscle blood flow and the cardiovascular response to exercise** Regulation · During exercise the heart pumps up to four or five times more blood and the working muscles take…](https://durgical.com/en/physiology/muscle-blood-flow-and-the-cardiovascular-response-to-exercise/) - [**Nervous control of the circulation and the CNS ischemic response** Regulation · The brain raises or lowers blood pressure within seconds through the sympathetic nerves and the…](https://durgical.com/en/physiology/nervous-control-of-the-circulation-and-the-cns-ischemic-response/) - [**Other cardiovascular reflexes: chemoreceptor, atrial (Bainbridge), muscle and pressure waves** Regulation · Besides the baroreflex, sensors of blood gases, atrial stretch and brain signals also steer…](https://durgical.com/en/physiology/other-cardiovascular-reflexes-chemoreceptor-atrial-muscle-and-pressure-waves/) - [**Physiology of congenital shunts** Mechanism · A hole between the two halves of the heart or the great vessels lets blood flow from the…](https://durgical.com/en/physiology/physiology-of-congenital-shunts/) - [**Physiology of hypertension** Mechanism · Hypertension is sustained high blood pressure; almost always, a kidney needs more pressure to…](https://durgical.com/en/physiology/physiology-of-hypertension/) - [**Preload, afterload and contractility** Concept · How much each beat pumps depends on how full the heart is, how hard it must push, and how strong…](https://durgical.com/en/physiology/preload-afterload-and-contractility/) - [**Sinus, junctional and escape rhythms** Regulation · The sinus node sets the pace and speeds up or slows down with need](https://durgical.com/en/physiology/sinus-junctional-and-escape-rhythms/) - [**The cardiac electrical axis** Measurement · The axis is the average direction in which ventricular depolarization travels; you work it out…](https://durgical.com/en/physiology/the-cardiac-electrical-axis/) - [**The ECG in chamber hypertrophy and low-voltage states** Measurement · More heart muscle makes bigger ECG waves; fluid, air, fat or scar between heart and skin makes…](https://durgical.com/en/physiology/the-ecg-in-chamber-hypertrophy-and-low-voltage-states/) - [**The ECG in ischemia and infarction** Measurement · When heart muscle runs short of blood, the ST segment, T wave and Q wave change, and point to…](https://durgical.com/en/physiology/the-ecg-in-ischemia-and-infarction/) - [**The ECG in potassium and calcium disorders** Measurement · Potassium and calcium reshape the cardiac action potential, and it shows in the T wave, the QRS…](https://durgical.com/en/physiology/the-ecg-in-potassium-and-calcium-disorders/) - [**The layout of the circulation: vessel segments, pressures and how flow is measured** Concept · Blood runs through two circuits in series](https://durgical.com/en/physiology/the-layout-of-the-circulation-vessel-segments-pressures-and-how-flow-is-measured/) - [**The microcirculation: capillary types, vasomotion, diffusion and the interstitium** Concept · Capillaries are thin tubes where blood swaps gases, nutrients and water with the tissue](https://durgical.com/en/physiology/the-microcirculation-capillary-types-vasomotion-diffusion-and-the-interstitium/) - [**The response to standing up** Regulation · When you stand, blood drops into the legs; fast reflexes speed the heart and tighten the vessels…](https://durgical.com/en/physiology/the-response-to-standing-up/) - [**Vascular compliance and capacitance** Concept · Arteries are elastic and cushion each beat; veins are so stretchy that they hold most of the…](https://durgical.com/en/physiology/vascular-compliance-and-capacitance/) - [**Venous return and the Guyton curves** Mechanism · The heart can only pump the blood that reaches it](https://durgical.com/en/physiology/venous-return-and-the-guyton-curves/) ## For completeness - [**Cardiac work, oxygen use and efficiency** Concept · The heart spends energy to push blood against pressure](https://durgical.com/en/physiology/cardiac-work-oxygen-use-and-efficiency/) - [**How specific hypertensions arise: volume loading, Goldblatt kidney, obesity, neurogenic and monogenic** Mechanism · Each kind of high blood pressure ends the same way: the kidney needs a higher pressure to…](https://durgical.com/en/physiology/how-specific-hypertensions-arise-volume-loading-goldblatt-kidney-obesity-neuroge/) - [**How the lymphatic system works** Concept · Lymphatics collect the fluid and proteins that leak out of capillaries and return them to the…](https://durgical.com/en/physiology/how-the-lymphatic-system-works/) - [**Long-term flow control: angiogenesis, collaterals and vascular remodelling** Regulation · Over days to months, tissues grow new vessels when short of oxygen, open side channels around…](https://durgical.com/en/physiology/long-term-flow-control-angiogenesis-collaterals-and-vascular-remodelling/) - [**Myocardial metabolism and the neural control of coronary vessels** Concept · The heart runs mostly on fat and needs oxygen every beat](https://durgical.com/en/physiology/myocardial-metabolism-and-the-neural-control-of-coronary-vessels/) - [**Peripheral venous pressure, gravity and the blood reservoirs** Concept · Standing makes the weight of blood push hard on leg veins](https://durgical.com/en/physiology/peripheral-venous-pressure-gravity-and-the-blood-reservoirs/) - [**Skin blood flow** Regulation · Skin gets far more blood than it needs for its own nutrition, because its flow is mostly used to…](https://durgical.com/en/physiology/skin-blood-flow/) ## A to Z - [A](https://durgical.com/en/physiology/a-z/a/) - [B](https://durgical.com/en/physiology/a-z/b/) - [C](https://durgical.com/en/physiology/a-z/c/) - [D](https://durgical.com/en/physiology/a-z/d/) - [E](https://durgical.com/en/physiology/a-z/e/) - [F](https://durgical.com/en/physiology/a-z/f/) - [G](https://durgical.com/en/physiology/a-z/g/) - [H](https://durgical.com/en/physiology/a-z/h/) - [I](https://durgical.com/en/physiology/a-z/i/) - [L](https://durgical.com/en/physiology/a-z/l/) - [M](https://durgical.com/en/physiology/a-z/m/) - [N](https://durgical.com/en/physiology/a-z/n/) - [O](https://durgical.com/en/physiology/a-z/o/) - [P](https://durgical.com/en/physiology/a-z/p/) - [R](https://durgical.com/en/physiology/a-z/r/) - [S](https://durgical.com/en/physiology/a-z/s/) - [T](https://durgical.com/en/physiology/a-z/t/) - [U](https://durgical.com/en/physiology/a-z/u/) - [V](https://durgical.com/en/physiology/a-z/v/) - [W](https://durgical.com/en/physiology/a-z/w/) [← Physiology](https://durgical.com/en/physiology/) Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given. Representative model, for educational purposes only. --- Source: https://durgical.com/en/physiology/areas/cardio/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/physiology/areas/cardio/