Physiology MCQ Answer 100

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  That’s the first phase defined as starting with the P wave.
  
  
  
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  As the electrical activity spreads over the atrium we have atrial contraction and a slight bump up of atrial pressure. This is the A wave (atrial contraction). We’ll talk about three different waves in atrial pressure during this cycle. First is the A wave during atrial systole. Then the atrial pressure curve when atrial contraction pushes blood into the ventricle and increases the pressure in the ventricle slightly during atrial systole. Sometime this is referred to as the atrial kick in the ventricular pressure, both during atrial systole.
  
  
  
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  Also the entrance of blood during atrial systole produces a heart sound not normally audible. It is the 4th heart sound.
  
  
  
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  At the end of this we have valve closure. AV valves close. This is the end of atrial systole.
  
  
  
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  Then we have the 1st heart sound again. There are some audible heart sounds such as the closure of the AV valves. There are other parts to this first heart sound that are inaudible, but can be measured. This is when you have ventricular contraction you reverse of blood flow from the atrium can cause turbulence and sound that are normally inaudible but considered part of the 1st heart sound. The audible part is produced by valve closure.
  
  
  
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  When the valve closes we are at our end diastolic volume. We know that a normal value for end diastolic volume (EDV) is 120 mL of blood.
  
  
  

Category: Physiology MCQs