Fases del Ciclo Cardiaco y el Esquema de Wiggers, Animación. Alila Medical Media Español.

Phases of the Cardiac Cycle and the Wiggers Diagram. This video and other related images/videos (in high definition) are available for instant licensed download here: https://www.alilamedicalmedia.com/-/g... Narrated by: Laura Mejia Translated from English by: Daniel Perez ©Alila Medical Media. All rights reserved. All images/videos by Alila Medical Media are for informational purposes ONLY and are NOT intended to substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified healthcare professional with any questions you may have regarding a medical condition. The cardiac cycle refers to the sequence of events that occur and repeat with each heartbeat. It can be divided into two main phases: systole and diastole, each of which is subdivided into several shorter phases. Systole and diastole, when not otherwise specified, refer to ventricular contraction and relaxation, respectively. Reminders: Blood flows from higher to lower pressure. Contraction increases the pressure within a chamber, while relaxation decreases pressure. The AV valves OPEN when atrial pressures are GREATER than ventricular pressures and CLOSE when the pressure gradient REVERSES. Similarly, the semilunar valves OPEN when ventricular pressures are GREATER than aortic/pulmonary pressures, and close when the reverse occurs. The cycle begins with the firing of the SA node, which stimulates the atria to depolarize. This is represented by the P wave on the ECG. Atrial contraction begins shortly after the P wave begins and causes the pressure within the atria to increase, forcing blood into the ventricles. Atrial contraction, however, is only responsible for a fraction of ventricular filling because at this point the ventricles are already nearly full due to passive blood flow into the ventricles through the open AV valves. As atrial contraction ends, atrial pressure begins to fall, reversing the pressure gradient across the AV valves, causing them to close. The closure of the AV valves produces the first heart sound, S1, and marks the beginning of systole. At this point, ventricular depolarization, represented by the QRS complex, is halfway complete, and the ventricles begin to contract, rapidly increasing the pressures within the ventricles. For a moment, however, the semilunar valves remain closed and the ventricles contract into a closed space. This phase is called isovolumic contraction because NO blood is ejected and ventricular volume DOES NOT change. Ventricular ejection begins when ventricular pressures EXCEED the pressures within the aorta and pulmonary artery; the aortic and pulmonary valves OPEN and blood is EJECTED out of the ventricles. This is the RAPID ejection phase. As ventricular repolarization, represented by the T wave, begins, ventricular pressure begins to fall and the force of ejection decreases. When ventricular pressure falls BELOW aortic and pulmonary pressures, the semilunar valves CLOSE, marking the end of systole and the beginning of diastole. The closure of the semilunar valves produces the second heart sound, S2. The first part of diastole is, again, isovolumetric, meaning the ventricles relax with ALL valves CLOSED. Ventricular pressures drop RAPIDLY, but their volumes remain the same. Meanwhile, the atria fill with blood, and atrial pressure slowly increases. Ventricular filling begins when ventricular pressures fall BELOW atrial pressures, causing the AV valves to open, allowing blood to flow PASSIVELY into the ventricles. The atria contract to complete the filling phase, and the cycle repeats.