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A coronary CT calcium scan is a computed tomography (CT) scan of the heart for the assessment of severity of coronary artery disease. Specifically, it looks for calcium deposits in atherosclerotic plaques in the coronary arteries that can narrow arteries and increase the risk of heart attack. [ 1 ]
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 ...
Positive Bowditch effect causes an increase in cardiac output due to the increased force of contraction of heart muscles. [7]This phenomenon is usually absent or even reversed (negative Bowditch effect) in heart failure and other diseases of heart, such as cardiomyopathy and coronary artery disease.
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.
Increase the amount of calcium in the sarcoplasm. More calcium available for Troponin to use will increase the force developed. Decreasing contractility is done primarily by decreasing the influx of calcium or maintaining lower calcium levels in the cytosol of cardiac myocytes during an action potential.
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 ...
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 .
Increased contraction increases the total peripheral resistance (TPR) and this further increases the mean arterial pressure (MAP). This is explained by the following equation: M A P = C O ∗ T P R {\displaystyle MAP=CO*TPR} , where CO is the cardiac output , which is the volume of blood pumped by the heart in one minute.