2. Conduction System
• To pump blood efficiently, both atria need to
contract at the same time, followed by
contraction of both ventricles (the cardiac
cycle)
3. Conduction System
• To pump blood efficiently, both atria need to
contract at the same time, followed by
contraction of both ventricles (the cardiac
cycle)
• Contraction is coordinated by the conduction
system, which carries the signal to contract
throughout the heart
4. Conduction System
• To pump blood efficiently, both atria need to
contract at the same time, followed by
contraction of both ventricles (the cardiac
cycle)
• Contraction is coordinated by the conduction
system, which carries the signal to contract
throughout the heart
• Intercalated disks allow signal to travel rapidly
between adjacent cells
5. Components of the Conduction System
1. Sinoatrial node: located on the posterior wall
of the right atrium, near the entrance of the
superior vena cava. Initiates impulses 70-80
times per minute. Pacemaker of the heart.
Impulses travel rapidly throughout the atrial
myocardium and cause the two atria to
contract simultaneously
6. Components of the Conduction System
1. Sinoatrial node: located on the posterior wall
of the right atrium, near the entrance of the
superior vena cava. Initiates impulses 70-80
times per minute. Pacemaker of the heart.
Impulses travel rapidly throughout the atrial
myocardium and cause the two atria to
contract simultaneously
2. Atrioventricular (AV) node: Located on the
floor of the right atrium. Cells in the AV node
conduct impulses slowly. This allows time for
the atria to finish contracting before the
ventricles begin contracting
7. 3. AV bundle (bundle of His): Conducts impulses
from atria to ventricles
8. 3. AV bundle (bundle of His): Conducts impulses
from atria to ventricles
4. Right and left bundle branches: extend down
the sides of the interventricular septum.
Branch profusely to form the conduction
myofibers
9. 3. AV bundle (bundle of His): Conducts impulses
from atria to ventricles
4. Right and left bundle branches: extend down
the sides of the interventricular septum.
Branch profusely to form the conduction
myofibers
5. Conduction myofibers (Purkinje fibers):
Transmit impulses throughout the ventricular
myocardium so that both ventricles contract
at the same time
11. Electrocardiograms (ECG or EKG)
• Impulses conducted through the heart during
a cardiac cycle produce electric currents that
can be measured on the surface of the body
to produce an electrocardiogram
12. Electrocardiograms (ECG or EKG)
• Impulses conducted through the heart during
a cardiac cycle produce electric currents that
can be measured on the surface of the body
to produce an electrocardiogram
• Diagram
13. Electrocardiograms (ECG or EKG)
• Impulses conducted through the heart during
a cardiac cycle produce electric currents that
can be measured on the surface of the body
to produce an electrocardiogram
• Diagram
• Useful in evaluating heart function. For
example, a heightened p wave indicates an
enlarged atrium
16. Cardiac Output
• Volume of blood pumped by a ventricle in 1
minute
• = Stroke volume (ml/cycle) x Heart Rate
(cycles/minute)
17. Cardiac Output
• Volume of blood pumped by a ventricle in 1
minute
• = Stroke volume (ml/cycle) x Heart Rate
(cycles/minute)
• Heart rate: SA node sets basic rate, but it can be
changed by the cardiac center in the medulla
oblongata. Rate increases in response to
epinephrine, low blood pressure, high CO2, low
pH, high temperature, emotions (fear, anxiety,
excitement, anger)
