Smorgasbord Health Column – Major Organs and Systems of the Body – The Heart and how it works – Sally Cronin

It is over two years since I focused on the heart, and in that time the statistics for heart health and deaths from heart disease have not improved dramatically. In fact recent research is indicating the increase in obesity rates is resulting in an increased risk of heart disease

We often refer to the heart as our emotional centre. When in fact our heart works in response to stimuli from our brains and the amount of blood that is pulsing through it via the circulatory system.

We can feel and hear our heart beating and it is perhaps only when we hear it miss a beat of have palpitations that we give it much thought. We can speed our heart rate, buy strenuous exercise for example, and also slow down (with practice) by using relaxing techniques and breathing exercises. However, the rest of the time it is on automatic pilot.

It is important to have some understanding of how the heart works, before moving on to working on strategies to keep it pumping for as long as possible.

The Heart.

The heart is the pump that powers the circulatory or cardiovascular system formed by a network of arteries, veins and smaller blood vessels. Blood is continuously pumped out from the heart around the venal and arterial circuits carrying oxygen and vital nutrients to all parts of the body. The arteries take the blood away from the heart and the veins bring the blood back.

Chest x-ray showing heart positionThe heart itself is a muscle, approximately the size of a clenched fist, and is shaped like a large upside down pear, located just to the left of the centre of the chest.

The heart weighs around 11 ounces or 310 grams and rests in a moist chamber, called the pericardial cavity, between the lungs and surrounded by the rib cage.

The muscle is called the myocardium and forms a shell around four cavities or spaces inside the heart that fill with blood. The two upper cavities are called atria and the bottom two spaces are called ventricles. Each side of the heart is separated by a wall called the septum and a valve connects each atrium to the ventricle below it. The valve on the left side of the body is called the mitral valve and the right side connection is called the tricuspid valve. The Endocardium lines the inside of the heart, and the heart valves, and the pericardium is a fibrous sac surrounding the heart.

Heart labelledThe top of the heart is connected to some major blood vessels – the largest being the aorta, or main artery, which carries the nutrient rich blood away from the heart to the rest of the body. Another important blood vessel is the pulmonary artery, which connects the heart to the lungs.

The two largest veins that carry blood back to the heart are called the superior vena cava and the inferior vena cava. The superior vena cava takes de-oxygenated blood from the head and the arms to the right atrium, and the inferior vena cava brings de-oxygenated blood back up from the legs and lower body also into the right atrium.

The cardiac muscle contracts between 70 and 80 beats per minute and if it is to last the normal life-span it will beat over 3 billion times. This means that the muscle has to be incredibly strong and healthy.

De-oxygenated blood always returns to the body through the right side of the heart into the atrium and then onto the lungs to pick up the oxygen. It is then returned to the heart where it enters the left side into the atrium and ventricle to be pumped to all the other parts of the body in a continuous cycle.

How does the heart beat?

The heart beats automatically without our thought or intervention and the number of beats is maintained by an electrical impulse that originates from the body’s own natural pacemaker called the sinoatrial node. The electrical impulse is sent through the atria which stimulates a contraction then through to the atrioventricular node where it will pause for a fraction of a second before continuing down special conducting fibres to the ventricles, causing them to contract.

Specific nerves called autonomic nerves, the main one being the vagus nerve, regulate the amount of times our heart beats. The ideal rate is maintained at around 70 beats at rest but is then speeded up during exercise or stress. The cardiac nerves react to messages sent from the hypothalamus, in the medulla part of the brain, and the beat rate will also increase when the “fight or flight” hormone, adrenaline, is released. This increases the amount of blood and therefore oxygen that is made available to the heart and the rest of the body.

Risk factors for heart disease and stroke are largely similar for men and women.

  • Factors such as age and family history play a role, but it is estimated that the majority of CVD deaths are due to modifiable risk factors such as smoking, high cholesterol, unhealthy diet, high blood pressure, obesity, stress or diabetes
  • Heart disease was associated with men until the last twenty years and now cardiovascular disease (CVD) – heart disease and stroke – is the biggest killer of women globally, killing more women than all cancers, tuberculosis, HIV/AIDS and malaria combined.

Next time I will be covering Angina and other common heart health conditions.

©Sally Cronin Just Food for Health 1998 – 2019

My nutritional background

I am a qualified nutritional therapist with twenty years experience working with clients in Ireland and the UK as well as being a health consultant on radio in Spain. Although I write a lot of fiction, I actually wrote my first two books on health, the first one, Size Matters, a weight loss programme 20 years ago, based on my own weight loss of 154lbs. My first clinic was in Ireland, the Cronin Diet Advisory Centre and my second book, Just Food for Health was written as my client’s workbook. Since then I have written a men’s health manual, and anti-aging programme, articles for magazines and posts here on Smorgasbord.

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