Download The Conducting System and EKG

The
Conducting
System and
EKG
Danny Golinskiy, Joel Levy,
Emily Brames
The Conducting System
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Cardiac muscle contracts
regardless of neural input
(autorythmicity)
All cardiac contractions are
coordinated by the heart’s
conducting system
The conducting system is a network
of specialized cells that initiate and
distribute electrical impulses in the
heart
The network is comprised of two
cells that do not contract: nodal
and conducting cells
The Conducting System
 Nodal
cells establish the rate
of cardiac contraction
(located at the sinoatrial
and atrioventricular nodes)
 Conducting cells distribute
the contractile stimulus to
the general myocardium
 Major cardiac sites for the
conducting cells include the
AV bundle, bundle
branches, and Purkinje fibers
The Conducting System
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Nodal cells depolarize spontaneously and
generate action potentials at regular intervals
Nodal cells determine the heart rate by
sweeping the cardiac tissue
The normal rate of contraction is established
by pacemaker cells, which reach the action
potential threshold first, and are located in
the sinoatrial node, referred to as the cardiac
pacemaker
The Conducting System
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Pacemaker cells generate 70-80
action potentials a minute
through spontaneous and rapid
depolarization
The cells of the SA node, which
houses the pacemaker cells, are
connected to the larger
antrioventricular node (AV node)
AV nodal cells generate only 4060 action potentials per minute
and can become the primary
pacemaker cells if they do not
receive input from the SA node
The Conducting System
 From
the AV node action potential travels
to the AV bundle, which divides into left
and right bundle branches that radiate
across the inner surfaces of the ventricles
 It takes an action potential about 50
milliseconds to travel from the SA node to
the AV node
 The action potential travels through cell to
cell contact
The Conducting System
 Bradycardia:
the heart rate is slower than
normal (60bpm or less)
 Tachycardia: the heart rate is faster than
normal (100bpm or more)
 Ectopic pacemaker: the origin of
abnormal signals
Electrocardiogram (EKG or ECG)
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An EKG is a device that records the electrical
events of the heart.
Each time the heart beats a wave of
depolarization passes through the heart muscle &
this activity is recorded on the EKG.
Leads are placed on the chest & limbs to obtain
an EKG.
Electrocardiogram (EKG or ECG)
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EKG is “read” by medical personnel
to monitor the electrical activity of
a patient’s heart.
Each heart beat has the following
major components:
P-Wave – represents the
depolarization of the atria.
QRS Complex - results when the
ventricles depolarize.
T-Wave – indicates repolarization of
the ventricles , the ventricles are
returning to a resting state.
Electrocardiogram (EKG or ECG)
 When
analyzing an EKG, the
clinician measures voltage & size of
the different components of the
EKG.
 Electrocardiograms are also used to
diagnose cardiac arrhythmias.
Arrhythmias are abnormal patterns
of cardiac activity.
EKG and the Conducting
System
 The
image created
by the EKG depicts
the electrical cycle
of the heart.
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The electrical signals
are derived from a
release of electrical
potential from high
to low across the
heart.
EKG and the Conducting
System
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The 3 parts of the EKG:
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P-wave: electrical discharge
across the atriums
QRS-complex: this relates to
the electrical discharge or
depolarization of electrical
potential across the
ventricles.
T-wave: Repolarization of
heart, or restoring of the
electrical potential in the
membrane tissues of the
heart.
EKG and the Conducting
System
 In
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the atrium:
During the electrical
discharge
(depolarization),
discharged from the
SA node to the AV
node and spreads
from the right atrium
to the left atrium.
EKG and the Conducting
System
 The
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Ventricles:
QRS Complex: Electrical
discharge of potential
(depolarization) of the right
and left ventricles.
T-wave: Restores the
electrical potential
(repolarization) across the
ventricles through the heart.
Work Cited
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Bartholomew, Edwin F., and Frederic
Martini. Essentials of Anatomy & Physiology.
San Francisco, CA: Benjamin Cummings, 2007.
Print.
McDowell, Julie. Encyclopedia of Human
Body Systems. Santa Barbara: Greenwood,
2010. Print.
Whittemore, Susan, and Denton A.
Cooley. The Circulatory System. Philadelphia
[Pa.: Chelsea House, 2004. Print.
Work Cited (Images)
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