How much is the weight of the heart
Two separate circuits
The average heart is about the size of a fist and weighs around 300 grams, and when at rest it beats 70 to 80 times a minute. Protected from bumps and injuries, the heart sits a little to the left of the middle of the body, directly behind the sternum and ribs.
With two large and two small chambers each, the heart supplies two circuits: The right part of the heart pumps oxygen-poor, so-called venous blood into the lungs, where it releases the carbon dioxide it has brought with it and absorbs oxygen. This little circulation is called the pulmonary circulation.
The left partial heart pumps the oxygen-rich blood that comes from the lungs to the other organs, to the head, arms and legs. Each half of the heart consists of an atrium and a chamber (ventricle). The blood flow is regulated through the heart valves. They work like valves.
When the large chambers of the heart contract, the pressure in them exceeds the pressure in the pulmonary or body arteries. This opens the valves to these blood vessels and closes the valves to the atria. If the ventricles are then emptied, the pocket flaps prevent blood from flowing back into the ventricles.
Now the blood can flow from the atria into the heart chambers. Due to the different tasks, the two halves of the heart are different in size. The left half of the heart, which supplies the body's circulation, is significantly larger.
The sinus node determines the heartbeat
If you look for your heartbeat with a stethoscope, you will find that you can actually hear two tones that follow each other quickly. During the so-called systole, which lasts about a third of a second, the large chambers of the heart contract and pump blood into the circulation.
When they are empty, the atria contract in the subsequent diastole. This phase lasts about two thirds of a second. The atria and ventricles always fill and empty themselves alternately.
The heart muscles receive the impulses for this from a plexus of nerves in the right atrium, the sinus node. From the sinus node, they are further distributed into the individual chambers. The weak currents that flow can be derived from the skin and can be made visible on the screen with an electrocardiogram (EKG).
An experienced doctor can draw conclusions from this as to whether a heart is healthy and working smoothly, but can also identify past heart attacks.
Pacemakers help with a disturbed heart rhythm
The heart is controlled - in constant interaction with the brain - by the vegetative nervous system, which we cannot consciously or willingly influence.
The electrical impulses that cause the heart to beat, however, arise in the heart itself, so that even a heart detached from the body during a heart transplant will continue to beat as long as the oxygen supply is available.
If the heart rhythm is permanently disturbed, an electrical pacemaker can help. Pacemakers have been around since the late 1950s. Modern devices consist of a slightly oval disc the size of a two euro coin. They are implanted in the body below the collarbone and have a battery that lasts for several years.
Controlled by a computer, they only start when the natural heartbeat stops. You can also adapt your pace to the current power requirement.
How fast our heart beats depends on nerve stimuli, hormones and the heart's own control mechanism. If we are under stress or are afraid, our adrenal glands release the hormones adrenaline and noradrenaline.
Stimulated in this way, the heart can increase its performance from the usual five to six liters per minute to more than 20 liters in order to supply organs and muscles with oxygen and nutrients more quickly. Conversely, the pumping power and frequency are reduced at night.
Stress is poison for the heart
Is it perhaps also due to the old myths that cardiac surgeons enjoy a special reputation? Cardiac surgeons and cardiologists often have to deal with particularly grateful patients. Some people then take to heart what the doctor recommends: "Avoid unnecessary stress."
The heart is an extremely robust muscle, but it can also be damaged. Continuous psychological stress, for example, makes the heart sick. Stress is a natural reaction. It ensures that the heart muscle increases the blood supply. The body is then ready to flee.
However, if someone is constantly energized, the finely balanced system of messenger substances and receptors, which ensures the regular flow of the pumping heart, gets mixed up.
In stressful conditions, the body releases the hormones noradrenaline and adrenaline. These messenger substances reach the muscle cells via ion channels and influence the metabolism there.
Scientists assume that the potassium exchange, which is particularly important for the heart rhythm, can be disrupted. Potassium flowing into and out of the cell plays an important role in the contraction and relaxation of the heart muscle cell.
If the metabolism changes under stress conditions, this can lead to electrical overheating of the muscle cells and, as a result, to cardiac arrhythmias.
Occasionally there is an effect that scientists refer to as "broken heart syndrome". The symptoms are initially similar to those of a heart attack. However, the suspected infarction is not confirmed in the electrocardiogram (EKG).
An atypical, squid-like deformed heart is only revealed during a cardiac catheter examination. Scientists suspect that, for example, shock and the sudden release of stress hormones trigger something like muscle rigidity or cardiac stiffness. Once recognized, such stress-related cardiomyopathy can be treated with medication.
Cultural history of the heart
Even our ancestors knew about the importance of the heart. For us it has always been more than just a muscle made of flesh and blood. Countless myths and legends entwine around the heart. Our Christian view of the world says it is in the heart that the human soul lives.
We "take something to heart", greet each other "warmly" and are considered bad people who are "heartless". On the other hand, those who "have an open heart" show tolerance and are ready for dialogue. With the heart we associate feelings such as love and sadness, but also envy and hate.
The cultural history of the heart is ancient. The first clues can be found in the 5,000 year old traditions from Mesopotamia. We know from the ancient Egyptians that they removed all organs from their dead before embalming, only the heart remained in the chest cavity.
Many still see the Aztecs as particularly cruel today. With stone knives they cut the hearts of people alive from the breasts, so that they could be sacrificed to the gods while still warm and beating. Over the millennia, countless artistic and, above all, literary works were created in which the heart occupies a prominent place.
This does not only apply to the Christian culture of the West. In Islam, too, the heart is an organ of sensation, intuition and knowledge, but above all it is a place of the revelation of the divine will.
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