Download Cardiac Conduction System

Cardiac Conduction System
The Cardiac Cycle
• Made up of events that are required to
produce a single heartbeat
• Include periods of synchronized
contraction (systole) and relaxation
(diastole)
• What’s happening during each of the
following: atrial systole, atrial diastole,
ventricular systole, and ventricular
diastole?
General Info – Conduction
System
• Cardiac muscle tissue is specialized to
contract
• Once a rhythm is established, these cells
have the ability to continue to contract and
relax at the same rate until signaled to
change
• There is a cardiac center in the medulla
which monitors and makes changes to
heart rhythm, but once changed, the heart
maintains its own pace
Conduction System
Conduction System
• Sinoatrial Node (SA Node) – this is the heart’s
“natural pacemaker;” each contraction of the
heart is initiated here; an action potential
spreads through the atria causing contraction of
the myocardial walls
• Atrioventricular Node (AV Node) – the impulse
from the SA node travels here in about .04
seconds, this allows for the atria to contract and
fill the ventricles with blood, then the AV node
“fires” an impulse to the myocardium of the
ventricles
Conduction System
• Bundle of His and Perkinje fibers – these
are specialized cardiac muscle cells that
propagate the action potential through the
remainder of the heart
• Any region of the heart may function as a
pacemaker due to the interconnectivity of
the muscle fibers by way of intercalated
discs, but the SA node responds to
commands to changes sent from the brain
• Animation
Electrocardiogram (ECG)
• All of this electrical activity from action
potentials being spread throughout the
heart can be measured using an ECG
• ECGs come in many different varieties but
all detect and record electrical activity in
the heart
12 lead (sensor) Placement
Parts of a ECG Cardiac Cycle
Sample ECG Data
• The P-wave coincides with the beginning of
atrial systole
• The QRS complex coincides with ventricular
systole
• The T-wave coincides with ventricular
repolarization (recovery)
Defibrillation
• If there is a problem with
the heart rhythm it can
be “reset” by using a
defibrillator Fibrillation
• A defibrillator uses a
therapeutic dose of
electrical energy to
depolarize a critical
mass of heart tissue,
normal heart rhythm can
then be established by
the SA Node.
Artificial Pacemakers
• An artificial
pacemaker is
an electronic
device that can
substitute for a
SA Node when
areas of the
conduction
system don’t
function
properly