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One of the explanations for an increase in the intracellular calcium concentration is the inability of the Na + /K +-ATPase to keep up with influx of sodium at higher heart rates. When a higher heart rate occurs, for example due to adrenergic stimulation, the L-type calcium channel has increased activity.
These calcium ions bind to and open more calcium channels (called ryanodine receptors) located on the sarcoplasmic reticulum within the cell, allowing the flow of calcium out of the SR. These calcium ions are responsible for the contraction of the heart. Calcium also activates chloride channels called I to2, which allow Cl − to enter the cell ...
Myocardial contractility represents the innate ability of the heart muscle (cardiac muscle or myocardium) to contract.It is the maximum attainable value for the force of contraction of a given heart.
It employs pacemaker cells that produce electrical impulses, known as cardiac action potentials, which control the rate of contraction of the cardiac muscle, that is, the heart rate. In most humans, these cells are concentrated in the sinoatrial (SA) node , the primary pacemaker, which regulates the heart’s sinus rhythm .
Cardiac excitation-contraction coupling (Cardiac EC coupling) describes the series of events, from the production of an electrical impulse (action potential) to the contraction of muscles in the heart. [1] This process is of vital importance as it allows for the heart to beat in a
The rapid influx of calcium into the cell signals for the cells to contract. When the calcium intake travels through an entire muscle, it will trigger a united muscular contraction. This process is known as excitation-contraction coupling. [2] This contraction pushes blood inside the heart and from the heart to other regions of the body.
Calcium is a vital element for regulating the contraction and relaxation of the heart muscle. [6] Calcium sensitizers are medications that increase the responsiveness of heart muscle cells to calcium, enabling more forceful contractions while conserving energy. [49] Contraction of the heart muscle relies on electrical signals that trigger the ...
In other words, a quicker reduction in cytosolic calcium levels (because the calcium enters the sarcoplasmic reticulum) causes an increased rate of relaxation (a positive lusitropy), however, this also enables a greater degree of calcium efflux, back into the cytosol, when the next action potential arrives, thereby increasing inotropy as well.