Electrical Activity of
Heart
Presentation by:
Tarique Ahmad
John Frost
Grant Post
Ian Osborne
Introduction Video
Cardiac Conduction System:
http://www.youtube.com/watch?v=zdoSreUAt
hA
Conducting System
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also known as cardiac conducting system or
the nodal system
its a network of specialized cardiac muscle
cells that initiates and distributes electrical
impulses
includes:
Sinoatrial (SA) Node
o Atrioventricular (AV) Node
o Conducting Cells
 Bundle of his (hiss )/ Atrioventricular (AV) Bundle
 Purkinje Fibers
o
Continued...
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conducting system allows heart to be
automaticity, or autorhythmicity
o
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it contracts on its own, in absence of neural and
hormonal stimulation
actual contraction lags behind the
electrical pulse
o
due to time is takes calcium ions to enter the
sarcoplasm
http://www.ceufast.com/courses/239/04_Cardiac_Conduction_System.jpg
Sinoatrial (SA) Node
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In the upper part of the right atrium
specialized bundle of neurons known as the
sinoatrial node (SA node)
Acting as the heart's natural pacemaker,
o
"fires" at regular intervals to cause the heart to
beat at a rhythm of 60 to 70 beats per minute
AV / Atrioventricular Node
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Specialized Cardiocytes relay the
contractile stimulus to the AV bundle, the
bundle branches, the Purkinje fibers, and
the ventricular myocardium
Located between the atria and the
ventricles
There's a 100 millisecond delay once signal
is received at AV node
= 100
millisecond
long delay
Lasts a total of
225
Milliseconds
http://washingtonhra.com/16.html
Conducting Cells: Bundle of His
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Also known as the AV
bundle
Carry the contracting
stimulus from the AV
node to the Purkinje
Fibers
Separates into left and
right bundle branches,
which are spread across
the inner surfaces of the
left and right
http://www.ambulancetechnicianstudy.co.uk/card.html#.UXHG16KsiSo
Conducting Cells: Purkinje Fibers
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Located in the inner ventricle walls of the heart just
below the epicardium
Assist the conduction system in the synchronization of
contractions
Carry the electrical impulses from the Sinoatrial Node
to the Myocardium
Conduct action potentials
Electrocardiogram (ECG/EKG)
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graphic record of heart, monitored by
electrical activity of heart at certain
locations
Electrical events of heart are powerful
enough to be detected by electrodes on
body surface
http://smartmedicalindo.com/product_images/w/452/Schiller_Cardiovit_AT-
Continued...
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comparing information from different
locations to monitor and check performance
of heart
o
specific components can be checked as well
tracing varies on placement of electrodes,
also called leads
used to detect cardiac arrhythmias
o abnormal cardiac activity
Understanding an ECG/EKG
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P Wave- small wave that accompanies
depolarization of atria
QRS Complex- wave that appears after
contraction of ventricles
o
ventricles begin contraction at peak of R wave
T Wave- small wave that indicates
ventricular repolarization
http://www.usfca.edu/fac-staff/ritter/Image20.gif
Analyzing an EKG
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involves measuring size of voltage changes
determining temporal relations between
components
focus on amount depolarization during P
wave and QRS complex
POP QUIZ!!!
1. What is the pacemaker of the heart?
a.
Where is it located?
2. What does AV stand for?
a.
Where is the node located?
3. What does the bundle of hiss do?
4. Where are the Purkinje Fibers located?
5. What does ECG/EKG stand for?
Works Cited
Martini, Frederic H., and Edwin F. Bartholomew. Essentials of
Anatomy and Physiology. 4th ed. San Francisco: Pearson,
2007. Print.
Martini, Frederic H., and Judi L. Nath. Fundamentals of Anatomy and
Physiology. 8th ed. San Francisco: Prentice Hall, 2009. Print.