Lymphatic & Blood Systems
31st August 2017
Metabolic Syndrome
31st August 2017

The Human Heart


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The human heart is the engine that keeps you alive; just like the engine in your car, your heart needs looking after. If you don’t maintain the engine in your car, it could let you down. Equally, if you don’t look after and maintain your heart, that could let you down too.
If you put the wrong fuel in your car, the pipes taking fuel to the engine can cause things to clog up; and if you don’t maintain a healthy blood supply, your arteries can start to get blocked, leading to heart problems.

The heart is a muscle. To be medically correct, the muscle tissue is called the myocardium, more commonly referred to as the cardiac muscle. There are three types of muscle in the human body: skeletal muscles, smooth muscles and one cardiac muscle.
Skeletal muscles are used (along with many other muscles) in walking, lifting weights and many more functions; every movement of these muscles is voluntary. Smooth muscles, on the other hand, involve involuntary movements, and are found in organs such as the stomach, lungs, and intestines.
You can read more on skeletal muscles in other sections.

The Cardiac Muscle works totally differently from the other muscles in your body.
The brain can speed up or slow down your heart rate through the release of hormones and other factors, providing there is a supply of oxygenated blood from the lungs.
But the heart muscle can also continue to beat without any connection to the brain. The heart will beat on its own, at a set rate called the intrinsic heart rate, of around 100 beats per minute. This is referred to as automaticity.

The Heart is able to function as its own pacemaker, totally independent of the brain, which is why it's possible for the human body to still have a heartbeat even if the brain has died.


The heart is located between the lungs. Around 80% of the heart is close to the left lung, sitting just above the stomach and liver behind the breast bone. The adult heart is roughly the size of a large grapefruit and weighs around 10 ounces (or 283 grams)


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Interactive Heart Diagram

1. If you hover your mouse over a section in the diagram of the heart, it will highlight that section.

2. When the area is highlighted, you can click on it to reveal that part of the heart's function.

NOTE: If you do this in alphabetical order (A to P), the process of a single heartbeat is described step-by-step.

THIS DIAGRAM abbreviates what I’ve detailed earlier. It shows how blood travels through the arteries around your body and then returns via the veins to the Right Atrium, to receive a fresh supply of oxygen.

(A) Right Atrium

Deoxygenated blood from the upper body enters the Right Atrium (A).

(B) Superior Vena Cava

The deoxygenated blood from the upper body comes in from through the Superior Vena Cava (B).

(C) Inferior Vena Cava

Blood from the lower body enters the right atrium through the Inferior Vena Cava (C).

(D) Triscupid Valve & (E) Right Ventricle

As the heart contracts, a valve opens (D) and forces blood into the Right Ventricle (E).

(F) Pulmonary Valve

All the valves in the heart only allow blood to pass in one direction. Valve (F) opens and blood is ejected into the Pulmonary Artery, which then divides into the Left Pulmonary Artery (G) and Right Pulmonary Artery (H).

(G) Left Pulmonary Artery

When valve (F) opens it forces blood out into the Left Pulmonary Artery (G) and to the left lung, where the blood expels the Carbon Dioxide and receives freshly oxygenated blood.

(H) Right Pulmonary Artery

When valve (F) opens it forces blood out into the Right Pulmonary Artery (G) and to the Right lung, where the blood expels the Carbon Dioxide and receives freshly oxygenated blood.

(J) Left Pulmonary Veins

The oxygenated blood returns to the heart via the two Left Pulmonary Veins (J) entering the ...

(K) Left Atrium

... the Left Atrium (K) ...

(L) Right Pulmonary Veins

... and the two Right Pulmonary Veins (L) also entering the Left Atrium (K).

(M) Mitral Valve

Oxygenated blood from the Left Atrium (K) is then passed through the Mitral Valve (M) ...

(N) Left Ventricle

... to the Left Ventricle (N).

(O) Aortic Valve

Freshly oxygenated blood from the Left Ventricle is then pumped out through valve (O) into the Aorta (P) to start its journey round the body again.

(P) Aorta

... via the Aorta (P) to start its journey again at the Right Atrium (A).

It’s hard to believe that all of what I’ve described above happens in one heartbeat!


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A heart attack, medically referred to as a myocardial infarction, is a serious medical emergency. In simple terms the heart will start to fail if there is a blockage in the arteries, stopping oxygen rich blood reaching the heart, and causing the heart muscle to start dying. Should this happen immediate treatment is required; a fast response is required to stop or minimise damage to heart muscle, otherwise scar tissue will form.

Sudden Cardiac Arrest is a heart condition, sometimes referred to as a heart attack; this is wrong. Sudden Cardiac Arrest (SCA), is not a heart attack. SCA starts when the electrical system inside the heart becomes faulty.
The human heart has its own built-in pacemaker called the SA Node. This node sends out electrical impulses in a continuous rhythm to the AV Node, which conducts the impulses to the ventricles, causing the heart muscle to contract; this results in your heart beating around 70 beats per minute.
It’s worth mentioning that the human brain is not responsible for the beat of your heart; however the brain together with hormones do influence the heart rate.

When the rhythm of the heart becomes abnormal, medically called an arrhythmia, this causes the heart either to beat too fast (called tachycardia) or too slow (called bradycardia).
The most common side effect of an arrhythmia, which is life threatening, is referred to as ventricular fibrillation. When this happens it can stop the ventricles in the heart from pumping blood, and blood pressure drops, resulting in loss of consciousness to the brain and organs. Without immediate treatment of CPR and a defibrillator, the brain dies.

Some research indicates that a high proportion of sudden cardiac arrest cases occur in the age bracket between mid-thirties and fifty, often with no history of heart disease.
It’s worth remembering:
Heart conditions can cause high blood pressure.
High blood pressure can cause heart disease.





Medically referred to as angina pectoris, Angina is a chest pain due to the lack of oxygen to the heart muscle. This condition can feel like pressure on your chest, due to the lack of oxygen, or feel like being suffocated. Any of these symptoms should be checked, as it’s possible it could lead to a heart attack. Angina is also related to blood pressure; the higher the blood pressure the more symptoms it will cause. Higher than normal blood pressure puts a strain on the heart wall requiring more oxygen.

All our organs, which include the kidneys, liver, gall bladder, stomach, and others, require oxygenated blood to function correctly. However people with Coronary Heart Disease (CHD) have arteries which have plaque within them; the plaque can be caused by fatty deposits, and can cause narrowing of the arteries.
When arteries become partially blocked, exercise or anything that increases the heart rate means that the arteries can’t get enough fresh oxygenated blood to the organs. The medical term for this condition is ‘Cardiac Ischemia.’ When the volume of blood flowing through the arteries is reduced, the heart in turn doesn't receive enough oxygen; this condition is referred to as Angina. When resting, the heart rate goes down and the pain can subside.


Although there are many obvious causes of high blood pressure and heart disease, heart problems can also be caused by stress. If you are someone who has occasional stressful situations, then this section is possibly not so important....
However, it’s possible to become stressed to a level that it affects your health, for instance if you’re someone who leads a busy life at work, spends time driving to work and encountering traffic jams, maybe has personal problems or money worries, or you’re a Mum looking after children but still must work, cook and manage the house.

There is a lot of information on stress in section 19, but below I’ve included some information on hormones and the effect they have on the body.
Linking Stress to high blood pressure and heart disease is not straight forward. From research, there is no evidence that stress alone causes long term high blood pressure and in-turn heart disease. However, when the human body gets into a stressful situation it produces different hormones, below are a few examples:

Adrenaline, Norepinephrine, Cortisol

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Cortisol is a steroid hormone, when it’s used for medication it’s called hydrocortisone, this has many uses including, inflammation, arthritis, immune disorders and a lot more.
Cortisol is released into the blood stream under stressful situations, this hormone increases blood sugar but suppresses the body’s immune system. Cortisol is always present in the blood stream, the level of cortisol is higher in the morning, lower towards the end of the day, reducing even lower when we sleep.
More on sleep in section 25.

The levels of cortisol in the body shouldn’t be too low nor should they be too high, it’s when the levels are outside accepted levels the may kick in.
Cortisol plays an important part when the body is stressed, managing stress in the body by shutting down functions such as the reproduction and immune system; this assists our bodies to direct our energy and cope with stressful situations.
So far so good, the body is coping with the stressful situation; blood pressure will have risen and should reduce once the stressful situation is resolved and you are relaxed and in control.

However, should stress levels continue, even at a lower level day in day, cortisol can start to cause many problems, some of which are:
  • Cortisol causes ‘Gluconeogenesis‘, which is responsible for making glucose in your liver.
  • Cortisol can stop insulin from getting into the cells in your body, this results in glucose remaining in the blood stream, not good.
  • Cortisol can also shut down parts of the immune system which can leave your body open to infection.
  • Cortisol can cause the body to retain salt (Sodium) causing blood pressure to rise.
  • Cortisol can cause problems with the supply of thyroid hormones.
  • Cortisol can cause an increase in gastric acid which in turn can give problems with the intestines.
  • Cortisol in levels higher than normal can cause you to feel hungry and binge eat.
Cortisol is regulated by the Pituitary Gland which is located behind the eyes and is part of the Endocrine system; it is responsible for producing the hormones that control our bodies.

The objective of this web site

The objective of this web site is to provide information allowing people to understand in simple terms what happens to our bodies when things go wrong. This allows you to make informed decisions, and try and identify the possible causes of hypertension, heart disease and other conditions, as well as what can cause the body to retain fat and increase body weight. If the cause can be identified, then changing lifestyle can be a better solution than taking supplements and other medication.

Always remember

Always remember, if you experience chest pain you should seek urgent medical assistance. The good news is that in some cases, bypass surgery, stents and other procedures may help treat conditions relating to the heart. Should you have any concerns or questions about any information on this website, you should talk to your doctor or medical professional.

This web site will try and explain more about blood pressure and stress, explaining the possible damage to your heart. There is also a lot of information that may help in bringing down blood pressure and stress to acceptable levels and may also have an impact on your quality of life.
Stress seems to be part of our lives even when we try to remain calm. In the Members Section 19, there are suggestions how stress can be managed.
This whole website is all about keeping you informed and how you live your Life2Moro ®

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