CICLO CARDÍACO ¡fácil explicación! | Mentes Médicas

Understanding the Cardiac Cycle

Introduction to the Cardiac Cycle

• The cardiac cycle is introduced as a series of physiological events occurring from one heartbeat to the next, lasting approximately 0.8 seconds.

• Four key aspects are highlighted for understanding: names of each phase, pressure dynamics in atria and ventricles, blood flow direction, and valve states (open or closed).

Phases of the Cardiac Cycle

Systole and Diastole

• The cardiac cycle consists of two main phases: systole (contraction phase) and diastole (relaxation phase).

• Systole includes isovolumetric contraction and ejection phases; diastole involves isovolumetric relaxation, passive filling, and active filling.

Atrial Filling Phase

• The cycle begins with fully filled atria; atrial pressure exceeds ventricular pressure, causing atrioventricular valves to open.

• Blood flows passively from atria to ventricles during this phase, accounting for 80% of ventricular filling.

Active Filling Phase

• The active filling phase occurs when the atria contract, pushing an additional 20% of blood into the ventricles.

• This process is driven by increased atrial pressure due to atrial systole while maintaining open AV valves.

Ventricular Contraction Phases

Isovolumetric Contraction

• During isovolumetric contraction, ventricles are filled with approximately 120 milliliters of blood at end-diastolic volume.

• Ventricular pressure rises above atrial pressure leading to closure of AV valves; this closure produces the first heart sound (S1).

Ejection Phase

• With all valves closed during isovolumetric contraction, ventricular contraction increases pressure until it surpasses arterial pressure.

• Semilunar valves open allowing approximately 70 milliliters of blood (stroke volume) to be ejected into arteries.

Relaxation Phase

Isovolumetric Relaxation

• In this phase, the heart relaxes preparing for another cycle; arterial pressure exceeds ventricular pressure preventing backflow into the heart.

Understanding the Cardiac Cycle

The Role of Valves in Heart Function

• The concept of "valvular incompetence" is introduced, explaining how valves close to prevent blood from returning to the ventricles. This closure creates the second heart sound, known as S2.

• Valves function like small pouches that seal off when necessary, ensuring proper blood flow direction and maintaining efficient cardiac cycles.

Constant Volume and Cardiac Sounds

• The term "volumetric" is explained; it refers to a state where blood volume remains constant due to valve closures, which also produce distinct heart sounds during the cardiac cycle.

• Each time a valve closes, it signifies an important moment in the cardiac cycle, contributing to our understanding of heart sounds and their implications for health.

Sharing Knowledge on Cardiac Health

• The speaker encourages viewers to share this information with peers who may benefit from understanding the cardiac cycle better, emphasizing community learning.