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Transcript
PHYSIOLOGY OF THE HEART
NOTES
Cardiac Conduction System
• SA node - (pacemaker) sinoatrial
• AV node – atrioventricular
• AV bundle
Initiate and distribute impulses
throughout the myocardium
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.
AV node - atrioventricular
• Impulse
slowly moves
through this
node in right
atrium.
AV bundle
•
•
•
Located in
septum
End in purkinje
fibers - in both
ventricles
Ventricles are
stimulated to
contract.
Contractions
• Normal average 70-75
beats/min.
• Emotions, exercise, hormones,
pain, anxiety, fear, and anger
can affect this.
Electrocardiogram (ECG)
• Graphic record of the heart’s
action currents.
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.
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."
Electrocardiogram Waves
•
P-wave
– Depolarization
(contraction) of atria.
• QRS-wave
– Depolarization
(contraction) of
ventricle
• T-wave
– Repolarization
(relaxation) of
ventricles
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
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.
Blood Pressure
•
Sphygmomanometer measures air pressure
= to blood pressure
Blood Pressure
• Systolic pressure - 1st sound
– blood pushing against artery walls
when ventricles contract.
• Diastolic pressure - 2nd sound
– closing of valves, short sharp sound
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)
Video Clip
http://health.howstuffworks.com/heart4.htm
http://video.about.com/heartdisease/Congestive-Heart-Failure.htm
Congestive Heart Failure
Heart Attack
ECG