Table of Contents
What is the relaxation of the heart muscle?
Relaxation is the process by which heart muscle actively returns, after contraction, to its initial conditions of load and length. Over the past 25 years, physiologists, clinicians, and pharmacologists have shown increasing interest in trying to understand the regulation of myocardial relaxation.
What reflects the relaxation of the heart?
The P-V relation during early diastole reflects the lusitropic (relaxation) state of the heart, analogous to the inotropic (contraction) state measured during systole.
What is the term for myocardial relaxation?
Lusitropy is the rate of myocardial relaxation. The increase in cytosolic calcium of cardiomyocytes via increased uptake leads to increased myocardial contractility (positive inotropic effect), but the myocardial relaxation, or lusitropy, decreases.
How is the relaxation of cardiac muscle achieved?
Intracellular calcium is then removed by the sarcoplasmic reticulum, dropping intracellular calcium concentration, returning the troponin complex to its inhibiting position on the active site of actin, and effectively ending contraction as the actin filaments return to their initial position, relaxing the muscle.
What is the muscle layer of the heart called?
The muscles of the heart, termed the myocardium, make up the middle and thickest layer of the heart wall. This layer lies between the single-cell endocardium layer, which lines the inner chambers, and the outer epicardium, which makes up part of the pericardium that surrounds and protects the heart.
How do cardiomyocytes relax?
Pathway of Cardiac Muscle Contraction The actual mechanical contraction response in cardiac muscle occurs via the sliding filament model of contraction. In the sliding filament model, myosin filaments slide along actin filaments to shorten or lengthen the muscle fiber for contraction and relaxation.
What causes relaxation of heart?
The rate of relaxation is determined mainly by active Ca2+ pumping by the sarcoplasmic reticulum Ca2+ ATPase. Phosphorylation of phospholamban, a membrane-bound protein, removes its inhibitory effect on sarcoplasmic Ca2+ ATPase, thereby accelerating Ca2+ uptake and relaxation rate, especially under isotonic conditions.
What is muscle contraction and relaxation?
Muscle contraction is the activation of tension-generating sites within muscle cells. The termination of muscle contraction is followed by muscle relaxation, which is a return of the muscle fibers to their low tension-generating state.