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Heart Structure and Function 101:

The Plumbing and Wiring Systems of Your Heart

The heart is the most important muscle in the body. Yes, it is a striated muscle that functions and contracts similarly to an arm muscle, or a leg muscle. However, as we know, it has the very unique ability to contract tirelessly at a constant beat, pushing blood, oxygen and nutrients to the rest of our muscles, tissues and cells so that the body can function as a whole unit. The heart is made up of two very important systems: these can be thought of as an electrical system and a plumbing system. The electrical system is comprised of various nodes, or “switches,” and fibres, or “wires.” When activated, the switches or nodes send an electrical current down the wires or fibres; these fibres then affect the electrolyte concentrations in the tissues, resulting in a muscular contraction.

The Electrical System of the Heart

There is a small nerve-rich area just above the right atrium called the sinoatrial (SA) node (see Figure 1). This node is the original pacemaker, initiating its own electrical impulse that causes both atria to contract.


Figure 1. The “plumbing” and the electrical systems of the heart muscle.

This “electrical shock” squeezes the atria, forcing blood through the one-way valves into the ventricles. The electrical impulse then travels to another node called the atrioventricular (AV) node, where the impulse is briefly delayed while the atria finish emptying into the ventricles. Then the AV node quickly transmits the signal to another bundle of nerve fibres called the Bundle of His, and subsequently into fibres that surround the right and left ventricles called bundle branches and Purkinje fibres, causing the ventricles to squeeze blood out into each of the coronary arteries, the pulmonary artery and the aorta. Then, the same process begins all over again, occurring an average of 60-80 times per minute at rest in a healthy person.The electrical system is a complicated but fascinating phenomenon. It is governed by the exchange of minerals called electrolytes into and out of the cell. The main electrolytes in the body include sodium, potassium, chloride, calcium and magnesium. With the exception of the SA node, a nerve impulse is generated when a hormone stimulates a nerve cell, activating the exchange process of these electrolytes from one end of the nerve cell to the other and then into the next cell in a chain reaction.Electrolyte availability can heavily influence nerve signals and muscular effects. Sodium, potassium and chloride regulate nerve signal transmission. Calcium and magnesium regulate the resulting contraction and relaxation of a muscle. Too much or too little of any of these electrolytes can cause erratic signals and contractions, either directly in the heart or in the blood vessels.

The Plumbing System of the Heart

Now that we basically understand what initiates heart contractions, let’s look at where and how blood moves. When blood is forced by pressure from the pumping of the heart through the arterial system of the body, it delivers oxygen and nutrients to tissues. The blood accepts carbon dioxide and cellular waste from the tissues and then enters the venous system to dispose of this waste through the liver, kidneys and lungs and then return to the heart. The veins have a one-way valve system to prevent blood from flowing backward with the pull of gravity because they are not under pressure as the arteries are. Muscular contractions also help to “pump” blood in the veins back to the heart. This is why some people experience swollen feet if they sit too long, or faint if they stop immediately after a bout of physical exertion: the blood is pooling in the legs and is not being pumped back to the heart with the help of muscle contractions.Used blood that is devoid of oxygen and nutrients but rich in carbon dioxide returns from the body to the right side of the heart, is pumped through the arteries that bypass the lungs where it picks up oxygen, returns to the left side of the heart, and is then pumped back out to the body once again, and to the heart muscle itself.

Blood Vessels are Muscles, But They’re Part of the Plumbing System Too

There are several types of muscles. It was already mentioned that the heart is a striated muscle, just like the main arm and leg muscles that help us move. Blood vessels, however, are also made up of a type of muscle tissue called smooth muscle. These muscles also contract and relax, which in part helps regulate blood pressure. However, they can get blocked up by accumulating plaque or by a clot, just like a plumbing system can get clogged due to an accumulation of junk on the tube walls or due to a blockage. Plaque in the arteries is like a scab on the skin that results in a scar. It is an aggregation of immune cells, calcium and fatty substances like cholesterol that rush to the site of injury in an attempt to heal the tissue. If the site is reinjured, the scab gets bigger, blocking the artery, or a scar may form, making the tissue less flexible and therefore less functional.

What Does Nutrition Have To Do With It All?

Endothelial Health The fact is that more and more evidence is pointing toward healthy blood vessels being first and foremost in cardiovascular health. Blood vessel damage can cause plaque build-up, reduced vessel flexibility, reduced energy production by endothelial cells, and a compromised ability to heal. Getting the right nutrients ensures that blood vessels remain healthy and able to function and recover from injury appropriately. Some of these nutrients include vitamin C, nitric oxide, amino acids and antioxidants.

Blood Clotting The ability of the blood to clot normally is a huge health factor. Abnormal blood clotting can lead to either thickening or thinning of the blood, both of which are dangerous. Most clotting factors are immune cells of some sort. By modulating the production and activity of these clotting factors, certain well-known nutrients like vitamin K encourage healthy blood clotting, while others like omega-3 fatty acids and vitamin E promote thinning of the blood, and still many other nutrients have less well-known effects on the blood.


Figure 2. The importance of B-vitamins and branched-chain amino acids (BCAAs) in the energy production cycle. An example showing how nutrient deficiencies can affect energy production and cellular metabolism. Adapted from Ward D. Mitochondrial Restoration, Part I: Dysfunction, Nutrition, and Aging.

Electrical ActivityIons and minerals are vital to healthy nerve signal transmission and muscle contraction and relaxation. Deficiencies, overloads or imbalances of any of these minerals can lead to erratic nerve impulses, which can cause arrhythmias, and modifying arterial tension. As previously discussed, such minerals include magnesium, potassium, sodium, and calcium.

Cellular Metabolism General cellular metabolism depends on nutrition. Not only is getting sufficient energy important, but getting sufficient nutrition is equally if not more important! Getting the right nutrients gives cells what they need to make what the body requires to operate normally. Many vitamins and minerals and amino acids, for example the B-complex or magnesium, serve as co-enzymes for various metabolic reactions including energy breakdown or synthesis, methylation, homocysteine metabolism, and countless others (see Figure 2).

The Right Nutrients in the Right Amounts at the Right Time True Orthomolecular Medicine

Of course, we all know that eating the right foods is an integral part of keeping the cardiovascular system healthy. However, it is even more beneficial to get the optimal forms of nutrients when they’re needed the most in adequate quantities to best support the body.

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