Blood is carried in blood vessels. These are arteries and veins. Blood going to the heart is carried in veins. Blood going away from the heart is carried in arteries. The main artery going out of the right ventricle is the "pulmonary artery". (Pulmonary means about lungs.) The main artery going out of the left ventricle is the "aorta".
The veins going into the right atrium are the "superior vena cava" and "inferior vena cava". These bring blood from the body to the right heart. The veins going into the left atrium are the "pulmonary veins". These bring blood from the lungs to the left heart.
When the blood goes from the atria to the ventricles it goes through heart "valves". When blood goes out of the ventricles it goes through valves. The valves make sure that blood only goes one way in or out.
The four valves of the heart are:
The heart has three layers. The outer covering is the pericardium. This is a tough sack that surrounds the heart. The middle layer is the myocardium. This is the heart muscle. The inner layer is the endocardium. This is the thin smooth lining of the chambers of the heart.
A "heart beat" is when the heart muscle "contracts". This means the heart pushes in and this makes the chambers smaller. This pushes blood out of the heart and into the blood vessels. After the heart contracts and pushes in, the muscle "relaxes" or stops pushing in. The chambers get bigger and blood coming back to the heart fills them.
When the heart muscle contracts (pushes in) it is called "systole". When the heart muscle relaxes (stops pushing in), this is called "diastole". Both atria do systole together. Both ventricles do systole together. But the atria do systole "before" the ventricles. Even though the "atrial systole" comes before "ventricular systole", all four chambers do diastole at the same time. This is called "cardiac diastole"
The order is: atrial systole → ventricular systole → cardiac diastole. When this happens one time, it is called a "cardiac cycle".
Systole (when the heart squeezes) happens because the muscle cells of the heart gets smaller in size. When they get smaller we also say they "contract". Electricity going through the heart makes the cells contract. The electricity starts in the "sino-atrial node" (acronym SA Node) The SA Node is a group of cells in the right atria. These cells start an "electrical impulse". This electrical impulse sets the rate and timing at which all cardiac muscle cells contract. This motion is called 'atrial systole'. Once electrical impulse goes through the "atrio-ventricular node" (AV Node). The AV Node makes the impulse slow down. Slowing down makes the electrical impulses get to the ventricles later. That is what makes the ventricular systole occur "after" atrial systole, and lets all the blood leave the atria before ventricle contracts ("meaning squeeze").
After the electrical impulse goes through the AV Node, the electrical impulse will go through the "conduction system" of the ventricle. Conduction means heat or electricity traveling through something. This brings the electrical impulse to the ventricles. The first part of the conduction system is the "bundle of His". "His" is named for the doctor (Wilhelm His, Jr) who discovered it. Bundle means strings or wires grouped together in parallel. Once the bundle ("meaning a group of strings or wires going in parallel directions") goes through the ventricle muscle, it divides into two "bundle branches", the left bundle branch and the right bundle branch. The left bundle branch travels to the left ventricle and the right bundle branch travels to the right ventricle. At the end of the bundle branches, the electrical impulse goes into the ventricular muscle through the Purkinje Fibers. This is what makes ventricle contraction take place and makes ventricular systole.
The order is:
Sino-Atrial Node → Atria (systole) → Atrio-Ventricular Node → Bundle of His → Bundle branches → Purkinje Fibers → Ventricles (systole)
ECG is an acronym for ElectroCardioGram. It is also written EKG for ElectroKardioGram in German. The ECG shows what the electricity in the heart is doing. An ECG is done by putting electrodes on a person's skin. The electrodes see the electricity going through the heart. This is written on paper by a machine. This writing on the paper is the ECG.
Doctors learn about the person's heart by looking at the ECG. The ECG shows some diseases of the heart like heart attacks or problems with the "rhythm" of the heart (how the electricity goes through the heart's conduction system.)
The ECG shows atrial systole. This is called a P-wave. Then ventricular systole happens. This is called the QRS or QRS-complex. It is called a complex because there are three different waves in it. The Q-wave, R-wave, and S-wave. Then the ECG shows ventricular diastole. This is called the T-wave. Atrial diastole happens then too. But it is not seen separate from ventricular diastole.
The PR-Interval is the space between atrial systole (P) and ventricular systole (QRS). The QT-Interval is from when the QRS starts to when the T ends. The ST-segment is the space between the QRS and T.
Heart disease
Heart disease is a general term that means that the heart is not working normally. Babies can be born with heart disease. This is called congenital heart disease. If people get heart disease later, it is called acquired heart disease. Most heart disease is acquired.
The three most common types of acquired heart disease are:
A person can have heart disease and not feel sick. Some people with heart disease have symptoms. This is when there are changes or pain in the body to show a disease is there. Some symptoms of heart disease are:
Heart disease is the biggest killer of both men and women in the United States, England, Wales, and Canada. For example, heart disease causes 4 out of every 10 deaths in the United States. This is more than all kinds of cancer put together. Also, one person dies of heart disease about every minute in the United States alone.
Congenital heart disease refers to a form of heart problem that starts before birth (congenital). Congenital heart disease includes a large number of conditions. The formation of the heart before birth is very complex and is sometimes abnormal. For example, if a part of the main artery that comes from the heart is narrowed, that is called coarctation of the aorta. There may be holes inside the heart which keep the blood from flowing normally inside the heart. Other congenital heart problems are caused by abnormal heart valves. In some cases, congenital heart problems are discovered at birth. Other times the problems may not be detected until the person is an adult
North Dakota
North Dakota is a state in the United States. 672,591 people lived in North Dakota in the year 2010. The capital and seat of government is Bismarck.
North Dakota is south of Manitoba and Saskatchewan, east of Montana, north of South Dakota, and west of Minnesota. Manitoba and Saskatchewan are provinces - part of Canada. Montana, South Dakota, and Minnesota are other states in the United States.
North Dakota is not close to any big bodies of water (oceans or seas). Because of this, temperatures in North Dakota are "very" hot in the summer and "very" cold in the winter. In the summer, there are sometimes "strong" thunderstorms. These storms can have tornadoes and hail.
Before European people came, Native American people lived in the area now called North Dakota. One important tribe was the Mandan.
North Dakota was one of the last US states to be "settled". (To have people go there to make homes and live.) On November 2, 1889, North Dakota (and South Dakota) became part of the United States.