questions 2

Spread of Excitation

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Topic updated on 08/10/17 5:27pm

Overview
 

 
Spread of Excitation
  • Spread of Excitation 
    • SA node → atria → AV node → bundle of His → purkinje fibers → ventricle
  • cardiac action potential is initiated in myocardial cells in SA node 
    • spreads via gap junctions to myocardial cells of atria
  • a layer of fibrous, non-conducting tissue separates the atria and ventricles
    • consequently, cardiac action potential cannot spread directly from atria to ventricles
  • cardiac action potential spreads from atria to myocardial cells in AV node
  • cardiac action potential then spreads to bundle of His 
    • finally spreads to purkinje fibers that distribute action potential to ventricles
Conduction Velocity
  • Conduction velocity
    • bundle of His, purkinje fibers > atria > ventricles > AV node
  • slow conduction through AV node 
    • ensures that ventricles have sufficient time to fill with blood by contraction of atria 
    • before excitation and contraction to pump blood into systemic circulation

 



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Qbank (2 Questions)

TAG
(M1.CV.13) A researcher measures action potential propagation velocity in various regions of the heart in a 42-year-old Caucasian female. Which of the following set of measurements corresponds to the velocities found in the atrial muscle, AV Node, Purkinje system, and venticular muscle, respectively?

Topic Review Topic

1. 2.2 m/s, 0.3 m/s, 0.05 m/s, 1.1 m/s
2. 1.1 m/s, 0.05 m/s, 2.2 m/s, 0.3 m/s
3. 0.5 m/s, 1.1 m/s, 2.2 m/s, 3 m/s
4. 0.3 m/s, 2.2 m/s, 0.05 m/s, 1.1 m/s
5. 0.05 m/s, 1.1 m/s, 2.2 m/s, 3.3 m/s

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TAG
(M1.CV.118) A 32-year-old woman presents complaining of dyspnea, chest pain and fatigue. Her history is notable for an atrial septal defect at birth. On exam, she has a wide, fixed splitting of S2. Which part of pulmonary and cardiac systems has undergone irreversible changes? Topic Review Topic

1. Right atrium
2. Right ventricle
3. Pulmonary vessels
4. Aorta
5. Vena cavae

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