Craig C. Freudenrich
Discovery Fit & Health
Like all muscles, your heart cells have two sets of protein filaments that slide past each other, shorten (contract), and generate force. This is how your heart beats and pumps blood. And the trigger for the contractions is calcium. Here’s how it works:
1. Electrical signals generated in the heart travel across the heart muscle cells. They open tunnels in the cell membrane that let calcium ions flow inside the heart muscle cells from the outside.
2. Calcium ions enter the cell and cause the release of calcium from internal stores as well. The calcium levels inside the heart cell rise.
3. The calcium ions act as a switch. They “turn on” the interactions between the muscle filaments, thereby causing them to contract and generate force. The higher the calcium levels, the more force generated by the heart cells.
4. Once the electrical signals pass, the calcium channels close. Pumps on the cell membrane and internal stores pump calcium ions out of the cell and into the internal stores. The calcium levels around the filaments decrease.
5. Once the calcium levels decrease, the muscle filaments are “turned off.” The filaments slide back to their normal positions and the heart cells relax.
This process repeats itself every second.
So, as you can see, calcium regulates the strength of your heart beat. Your body can increase the strength of your heartbeat naturally by secreting hormones called epinephrine and norepinephrine. These hormones increase the levels of calcium in your heart cells and strengthen your heartbeats. Besides hormones, certain drugs can increase the calcium levels inside your heart. These drugs include digoxin and calcium channel blockers. They are useful in treating weakened hearts, such as those in congestive heart failure.
The strength of your heartbeat is greatly influenced by the amount of calcium that's found inside the cells of the heart's muscle. Calcium is an electrolyte, just like magnesium, potassium, sodium and chloride. These electrolytes are vital for ensuring that the kidneys, muscles, nerves and heart all function the way they're supposed to. Electrolytes are minerals that are derived from the foods and liquids we consume. These charged electrolytes generate the electrical impulses that cause muscles to contract. Calcium is particularly important to keeping your heartbeat strong.
When the heart begins to fail, doctors may prescribe digitalis compounds. Digoxin is one of these positive inotropic drugs that have proven effective in treating patients with severe cases of heart failure. The drug causes some side effects. For example, Digoxin can cause the heart to beat abnormally. This tends to occur when a patient's Digoxin dosage is increased significantly and suddenly. Digoxin poisoning also can result from high dosages of the drug. In extreme cases, when the level of toxicity exceeds a certain acceptable level, a patient will have to be taken off Digoxin. In some cases, the administration of anti-arrhythmic drugs and potassium supplements can alleviate some of these side effects. In the most severe cases, antibody fragments can be used to specifically counter the Digoxin.
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