Cardiac cycle physiology

[ "article:topic", "authorname:openstax", "ventricular ejection phase", "systole", "preload", "murmur", "isovolumic ventricular relaxation phase", "isovolumic contraction", "heart sounds", "end systolic volume (ESV)", "end diastolic volume (EDV)", "diastole", "cardiac cycle", "license:ccby", "showtoc:no", "transcluded:yes", "source[1]-med-756", "program:openstax", "licenseversion:40", "source@https://openstax.org/details/books/anatomy-and-physiology" ] Learning Objectives By the end of this section, you will be able to: • Describe the relationship between blood pressure and blood flow • Summarize the events of the cardiac cycle • Compare atrial and ventricular systole and diastole • Relate heart sounds detected by auscultation to action of heart’s valves The period of time that begins with contraction of the atria and ends with ventricular relaxation is known as the cardiac cycle (Figure \(\PageIndex\) ). The period of contraction that the heart undergoes while it pumps blood into circulation is called systole. The period of relaxation that occurs as the chambers fill with blood is called diastole. Both the atria and ventricles undergo systole and diastole, and it is essential that these components be carefully regulated and coordinated to ensure blood is pumped efficiently to the body. Pressures and Flow Fluids, whether gases or liquids, are materials that flow according to pressure gradients—that is, they move from regions that are higher in pressure to regions that are ...

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Learning Objectives By the end of this section, you will be able to: • Describe the relationship between blood pressure and blood flow • Summarize the events of the cardiac cycle • Compare atrial and ventricular systole and diastole • Relate heart sounds detected by auscultation to action of heart’s valves The period of time that begins with contraction of the atria and ends with ventricular relaxation is known as the cardiac cycle. The period of contraction that the heart undergoes while it pumps blood into circulation is called systole. The period of relaxation that occurs as the chambers fill with blood is called diastole. Both the atria and ventricles undergo systole and diastole, and it is essential that these components be carefully regulated and coordinated to ensure blood is pumped efficiently to the body. Figure 1. The cardiac cycle begins with atrial systole and progresses to ventricular systole, atrial diastole, and ventricular diastole, when the cycle begins again. Correlations to the ECG are highlighted. Pressures and Flow Fluids, whether gases or liquids, are materials that flow according to pressure gradients—that is, they move from regions that are higher in pressure to regions that are lower in pressure. Accordingly, when the heart chambers are relaxed (diastole), blood will flow into the atria from the veins, which are higher in pressure. As blood flows into the atria, the pressure will rise, so the blood will initially move passively from the atria into ...

https://med.libretexts.org/@app/auth/3/login?returnto=https%3A%2F%2Fmed.libretexts.org%2FBookshelves%2FAnatomy_and_Physiology%2FAnatomy_and_Physiology_(Boundless)%2F17%253A_Cardiovascular_System%253A_The_Heart%2F17.4%253A_Physiology_of_the_Heart%2F17.4B%253A_Electrocardiogram_and_Correlation_of_ECG_Waves_with_Systole \( \newcommand\) • • • • • • • An electrocardiogram, or ECG, is a recording of the heart’s electrical activity as a graph over a period of time. Key Points • An ECG is used to measure the rate and regularity of heartbeats as well as the size and position of the chambers, the presence of damage to the heart, and the effects of drugs or devices used to regulate the heart, such as a pacemaker. • The ECG device detects and amplifies the tiny electrical changes on the skin that are caused when the heart muscle depolarizes during each heartbeat, and then translates the electrical pulses of the heart into a graphic representation. • A typical ECG tracing of the cardiac cycle (heartbeat) consists of a P wave (atrial depolarization ), a QRS complex (ventricular depolarization), and a T wave (ventricular repolarization). An additional wave, the U wave ( Purkinje repolarization), is often visible, but not always. • The ST complex is usually elevated during a myocardial infarction. • Atrial fibrillation occurs when the P wave is missing and represents irregular, rapid, and inefficient atrial contraction, but is generally not fatal on its own. • Ventricular fibrillation oc...

The cardiac cycle refers to the sequence of events that takes place from one heart beat to the next. A full understanding of the cardiac cycle requires thorough examination of atrial systole, atrial diastole, ventricular systole, ventricular diastole, atrial and ventricular volume changes during the cycle, electrical events (depolarization and repolarization) of atria and ventricular myocytes, heart sounds associated with turbulent blood flow caused by the closure of semilunar valves, as well as hydrostatic blood pressure changes within the atria, ventricles, and the aorta. Test you basic understanding of the cardiac cycle by taking this simple quiz. (1) During ventricular systole of the cardiac cycle, the period of time immediately after the start of ventricular contraction when the atrioventricular valves close (when ventricular pressure exceeds atrial pressure) until just before the opening of the semilunar valves is referred to as the __________ __________ period. Your response should contain two words.