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  PHYSIOLOGY OF THE HEART NOTES
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Cardiac Conduction System

• SA node - (pacemaker) sinoatrial
• AV node atrioventricular
• AV bundle

Initiate and distribute impulses throughout the
myocardium
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SA node - (pacemaker) sinoatrial

• Initiates impulses that contract the heart
  without brain or nerve signals.
• Located at the right atrium
• Impulse travels to left atrium and contracts it.

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AV node - atrioventricular

• Impulse slowly moves through this node in right
  atrium.

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AV bundle

• Located in septum
• End in purkinje fibers - in both ventricles
• Ventricles are stimulated to contract.

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Contractions

• Normal average 70-75 beats/min.
• Emotions, exercise, hormones, pain, anxiety,
  fear, and anger can affect this.

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Electrocardiogram (ECG)

• Graphic record of the hearts action currents.

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Electrocardiogram (ECG)

• An ECG is printed on paper covered with a grid of
  squares. Notice that five small squares on the
  paper form a larger square. The width of a single
  small square on ECG paper represents 0.04
  seconds. To successfully interpret ECGs, you must
  have this value committed to memory.

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Electrocardiogram (ECG)

• If each small square represents 0.04 seconds,
  then a second will be 25 small squares across. If
  you print out a minute's worth of your heart's
  electrical activity, the paper would be 1500
  small squares wide. If something on an ECG is,
  let's say, 12 small squares in width, that means
  that it lasted 12 x 0.04, or almost half a
  second. A common length of an ECG printout is 6
  seconds this is known as a "six second strip."

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Electrocardiogram Waves

• P-wave
• Depolarization (contraction) of atria.
• QRS-wave
• Depolarization (contraction) of ventricle
• T-wave
• Repolarization (relaxation) of ventricles

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Cardiac cycle

• Atrial systole - contracting atria forces blood
  into ventricle. P-wave of ECG
• Isovolumetric contraction - blood volume in
  ventricles remains constant. QRS-wave of ECG
  (1st heart sound)
• Ejection - blood ejected into pulmonary artery
  and aorta. T-wave

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Cardiac cycle continued

• Isovolumetric relaxation - relaxation of
  ventricles (second heart sound)
• Rapid ventricular filling - return of venous
  blood
• Increases atrial pressure until av valves
  (tricuspid and bicuspid) open and blood rushes
  into ventricles.
• Reduced ventricular filling - increase in
  ventricular pressure and volume will slow blood
  filling.

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Blood Pressure

• Sphygmomanometer - measures air pressure to
  blood pressure

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Blood Pressure

• Systolic pressure - 1st sound
• blood pushing against artery walls when
  ventricles contract.
• Diastolic pressure - 2nd sound
• closing of valves, short sharp sound

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Directions for Taking Blood Pressure

• Pump pressure until no pulse is heard
• Release air until a spurt of blood is heard
  coming through. (systolic)
• Continue until sound stops (diastolic)

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Video Clip

• http//health.howstuffworks.com/heart4.htm
• http//video.about.com/heartdisease/Congestive-Hea
  rt-Failure.htm
• Congestive Heart Failure
• Heart Attack
• ECG