THE HUMAN HEART
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.
WHERE IS THE HEART LOCATED?
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)
HOW DOES THE HEART WORK?
The walls of the heart are muscle and like other muscles in your body it needs to be exercised to keep it strong and healthy. A sedentary life style and no physical activity may double your chances of heart disease.
People don’t need to be super athletes to keep the heart muscle exercised; just 30 minutes a day of brisk walking, maybe running up the stairs instead of taking the lift, can make a difference.
Exercise helps to strengthen the heart muscle, this can make it more efficient and able to pump more blood to the organs in your body. When the brain senses that more blood than is needed is reaching the body’s organs, the brain tells the heart to beat slower, which also reduces blood pressure.
HEART, LUNGS AND CIRCULATORY SYSTEM
The cardiac muscle (or Heart) has four sections and two pumps that squeeze and pump blood around the Circulatory System. The right atrium receives blood from the veins, people call this ‘Blue Blood’ meaning that it is deoxygenated; the blue blood from the lower body enters the right atrium of the heart via the Inferior Vena Cava, while the blue blood from the blue blood from the upper body enters the right atrium of theheart via the Superior Vena Cava.
This blue blood passes through a one-way valve into the right ventricle, the heart then pumps blood in need of oxygen through another one-way valve to the pulmonary artery, which in turn divides into the right and left pulmonary arteries that connect to the left and right side of your lungs.
The lungs then remove the carbon dioxide when you breathe out; when you breathe in again, fresh air comes into the lungs and is then taken via the left and right pulmonary veins into the left atrium of the heart.
The heart pumps fresh blood via a one way valve into the left ventricle of the heart, which in turn pumps fresh oxygenated blood via another one way valve into the main artery, called the aorta, supplying fresh blood to your brain and every organ in your body.
If you have a normal heart beat around 70 beats per minute, every action detailed above happens in less than a second, that’s 100,800 times every day, around 3.7 Billion times a year, and even more when your heart rate increases.
Life2Moro ®'s INTERACTIVE HEART DIAGRAM
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.
... 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!
WHAT IS A HEART ATTACK?
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.
SYMPTOMS OF A HEART ATTACK
Unfortunately people can mistake a heart attack for indigestion; some symptoms can be similar, especially a chest pain or a discomfort in the chest. Chest pain appertaining to the heart normally affects the centre and left side of the chest, however indigestion can also cause similar symptoms.
Another indication of a heart attack is discomfort in the left arm, or possibly both arms, a tight feeling in the jaw; other areas affected can be the neck and shoulder.
Other types of common symptoms include a cold sweat, possibly a shortness of breath, a feeling of nausea or feeling dizzy.
NOTE: If chest pain is accompanied by any of these common symptoms, medical assistance should be your first priority.
WHAT IS ANGINA?
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.
DANGER OF STRESS!
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
Adrenaline, also known as Epinephrine, is often referred to as the “Fight or Flight Hormone”. As a point of interest, the word Adrenalin without an ‘e’ was originally the trade mark of the Parke Davis & Co a pharmaceutical company founded in 1860 in Detroit USA.
Adrenaline is produced in the Adrenal Glands when a message is received from the brain that the body is under stress in some way.
When adrenaline gets into the bloodstream, people have been known to be able to lift weights far heavier than they can normally. Adrenaline also gives you the energy to run away from danger, and will raise your blood pressure while a stressful situation remains.
There is more about Adrenaline in Section 26.
Norepinephrine, is a hormone that reacts in a similar way to adrenaline, should the body become stressed or threatened, the brain releases norepinephrine into the blood stream, this hormone focuses your mind, makes you alert and ready to react to whatever stressful situation you’re faced with.
And like adrenaline your heart rate increases, glucose is released into the blood stream and again your blood pressure rises.
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.