Read the summary and the most important questions on H18: Het cardiovasculaire systeem

• 1 Cardiac function

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• Name all the components of the human heart

  • 2 upper chambers, atria (receive blood) and 2 lower chambers, ventricles (pump away blood).
  • Septum is the wall that separates the left and right halves.
  • Pulmonary arteries and veins connect with the lungs.
  • Left AV valve (mitralis) and right AV valve (tricuspidalis).
  • Chordae tendineae connect the papilllary muscles to the AV valves. 
  • Wide upper pole of the heart is the base and he narrow lower pole is the apex.

• Of what 2 divisions does the circulatory system consist? Explain how the blood flows through both systems.

  • The pulmonary circuit: consists of all blood vessels in the lungs and all those that connect the lungs to the heart,
  • The systemic circuit: encompasses the rest of the blood vessels in the body. 

  
  
  

  1. Blood flows from the lungs through the pulmonary veins to the left atrium and then the left ventricle.
     
  2. Blood flows from the left ventricle through the aorta to the body and then through the venae cavae (superior and inferior) to the right atrium and then the right ventricle.
  3. Blood flows from the right ventricle through the pulmonary arteries to the lungs. 

• How does the heart obtain its nourishment?

  • The blood within the hearts chambers do not provide enough oxygen and nutrients. 
  • It obtains most nourishment from the coronary arteries, which branch off near the aorta base and run through the aorta muscle. 
    
  • Also the circumflex artery and the left anterior descending artery.
    

  
  Decrease in blood flow through the coronary arteries can cause a heart attack.

• Which 2 organs are not in parallel but in series in the cardiovascular system?

  The intestines and the liver both have a portal circulation. This means that blood flows from one capillary bed to another before returning to the heart.

• Where is the heart located?

  The heart is located in the thoracic cavity, just above the diaphragm. It is surrounded by a membranous sac called the pericardium, which contains pericardial fluid that lubricates the heart as it beats.

• 2 Cardiac function

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• How are the AV valves connected/anchored?

  They are connected to the papillary muscles by chordae tendineae and they are anchored at their bases to rings of connective tissue formed by the fibrous skeleton.

• What are conduction fibers?

  • They are specialized to quickly conduct the action potentials generated by the pacemaker cells from place to place throughout the myocardium, thereby triggering heart muscle contractions. 
    
  • They are larger in diameter and can conduct APs more quickly than ordinary fibers. 

• Explain the sequence of electrical events that normally triggers the heartbeat.

  1. AP is initiated in the SA node. From the SA node the AP travels through internodal and interatrial pathways.
  2. Impulse arrives at AV node. Impulse is delayed because the AV node is slower (AV nodal delay). 
  3. Impulse travels through the bundle of His.
  4. It then splits into left and right bundle branches.
  5. Impulse then travels through Purkinje fibers and from here through the rest of the myocardial cells.

• Why is the heartbeat almost always triggered by the SA node and not the AV node?

  Because:
  

  1. APs originating in the SA travel through the VA, causing the cells in the AV to go into the refractory period.
  2. SA has a higher "beat frequency" than the AV.
     

• Where are the electrodes placed for an ECG? Which leads does this create?

  On the corners of Einthoven's triangle:
  

  • Right arm
  • Left arm
  • Left leg

  You then have:
  

  1. Lead I: LA-RA
  2. Lead II: LL-RA
  3. Lead III: LL-LA