B3: The Circulatory System 2

Heart Rate
1. Heart rate changes according to what you are doing. When you exercise, your heart rate increases as your muscles need more oxygen and the heart has to supply that via the blod,
2. The heart has a pacemaker
  1. The heart is told how fast to beat by a group of cells called the pacemakers. These cells produce a small electric current which spreads to the surrounding muscle cells making them contract.
  2. There are two clusters of these cells in the heart:
    1. The sino-atrial node (SAN)
    2. The atrio-ventricular node (AVN)
    3. The SAN always produces an electrical current first. This contracts the atria and pumps blood through the valve to the ventricles. The AVN then produces an electrical current and the ventricles contract, pumping blood out of the aorta or the pulmonary artery.
  3. Artificial pacemakers
    1. Sometimes if the AVN or SAN cells are not working properly, people will be given an artificial pacemaker. It is used to control the heartbeat, and is implanted under the skin and has a wire meeting with the heart. It produces an electric current and contracts the muscles.
3. You can measure heart rate using a variety of techniques:
  1. ECGs
    1. ECGs show the electrical activity of the heart, they can show heart attacks, or irregular heartbeats to conclude the general health of the heart.
      1. P = atrium contract.
        R = ventricles contract.
        T = ventricles relax.
        This is one heartbeat.
  2. Echocardiogram is an ulstrasound scan of the heart. They can show
    1. An enlarged heart:
      1. This could indicate heart failure.
    2. Decreased pumping ability
      1. This could indicate if you have any diseases affecting the pumping ability of the heart.
    3. Problems with valves
      1. torn or infected valves can cause problems with blood flow.
Blood pressure
1. The blood has the be at a high pressure as it has to travel a long way around the body. Your heart beats continuously to keep blood moving.
2. When your heart muscle contracts, blood is forced out of the heart and this increases the pressure of the blood.
  1. When the heart muscle relaxes the heart fills with blood and the blood pressure decreases.
3. You can measure your blood pressure by taking a reading of the pressure of the blood against the walls of an artery.
4. Blood pressure has two values. One's can be wrriten as 135 over 85. The higher value is the pressure of the blood when the heart contracts, and the lower value is the pressure of the blood when the heart relaxes.
5. A person's heart rate and blood pressure can be taken to see how healthy their heart is. A normal heart rate is about 60-100bpm as everyone is different.
6. The inner lining of an artery is smooth, but high blood pressure can damage it. High blood pressure can damage the artery and let fatty deposits build up. If this happens to a coronary artery (an artery that supplies the heart muscle with blood), then the muscles will not receive oxygen and will stop functioning. This stops an area of the heart from working and causes a heart attack.
Heart Disease
1. Heart disease can be caused by a variety of lifestyle factors and genetic factors. Epidemiological studies is the study of patterns of diseases and the factors that affect them.
2. Poor diets are a lifestyle factor of heart disease. If you eat lots of fatty foods or foods high in cholesterol, they could block arteries and cause problems. A poor diet increases the chance of heart disease
3. Stress increases blood pressure. If someone is stressing over a long period of time this risen blood pressure can damage arteries and allow fatty deposits to build up. This increases the chance of heart disease.
4. Cigarettes contain carbon monoxide and nicotine. Carbon monoxide reduces the amount of oxygen the red blood cells can carry, this means if the heart muscle doesn't get enough oxygen, it can lead to a hart attack. Nicotin
5. Misuse of illegal drugs like ecstasy and cannabis increase your heart rate making your blood pressure risen, meaning there is an increase of risk of heart disease. This is the same with alcohol which also risens the blood pressure.
6. Epidermologists study diseases and their causing factors. They can take genetic studies of all people with heart disease and ses if a gene causes the disease or contributes to it, or they can look at the similarities in lifestyle and diet between people with heart disease too to see the common cause of a disease.
Circulatory aids
1. If you lose a large volume of blood, you can be injected with a salt solution to add that volume for the heart to keep pumping the red blood cells around your body. This will give you time to regenerate the cells without the need of a transfusion. If not, a transfusion may be needed. An ideal artificial blood product would be ones that could replace red blood cells, but right now there are many side effects to it.
2. Artifical hearts are also mechanical fixes for faulty hearts and are used a temporary solution until a donor is found. Or sometimes they are permanent, meaning a donor is not needed.
  1. Pros:
    1. The mechanical heart is not rejected by the body's immune system.
  2. Cons:
    1. The mechanical heart could fail with an electric motor.
      1. Blood doesn't flow as well as in the real heart, so drugs need to be taken to thin it. This is dangerous if you get cut.
  3. Mechanical valves are easier to change, but there are still infectious problems with surgery and drugs need to be taken.
  4. Using stents:
    1. Stents are small tubes that are placed into the body to open up an artery.
    2. Sometimes, if there is a high deposit of fats in an artery, the blood pressure will increase and there will be a bigger chance of heart disease. If the fatty deposit is in the coronary artery, it could be very dangerous. So, a stent is placed in the artery which squashes the fat deposit and opens up the vein again for more blood flow.
      1. It's good because it lowers the chance of heart disease and could stop a heart attack.
        But it is bad as the stent could irritate the artery and make scar tissue grow. Also, blood flow may be slowed down so drugs need to be taken to thin the blood.

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B3: The Circulatory System 2

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	Created by Nikita Sitinikovs about 7 years ago