isovolumic

Isovolumic refers to a process or condition in which volume remains constant. This term is commonly used in physics, engineering, and physiology, particularly in the context of thermodynamic cycles and cardiac function.

In thermodynamics, an isovolumic process is one that occurs within a closed system where the volume does not change. This is one of the four basic processes in thermodynamics, alongside isobaric (constant pressure), isothermal (constant temperature), and adiabatic (no heat exchange). Isovolumic processes are often depicted on pressure-volume diagrams as vertical lines, indicating that the volume remains constant while the pressure may vary.

In the context of the cardiac cycle, isovolumic phases refer to periods when the heart's ventricles are either contracting or relaxing, but the valves are closed, resulting in no change in volume. The two main isovolumic phases are isovolumic contraction and isovolumic relaxation. During isovolumic contraction, the ventricles contract, increasing the pressure inside them, but the volume remains constant until the pressure exceeds that in the arteries, at which point the aortic and pulmonary valves open, allowing blood to be ejected. Conversely, during isovolumic relaxation, the ventricles relax and the pressure within them drops, but the volume remains constant until the pressure falls below that in the atria, causing the mitral and tricuspid valves to open, allowing the ventricles to fill with blood.

Understanding isovolumic processes is crucial in various fields, including engine design, refrigeration cycles, and cardiovascular physiology.