Download The Cardiac Conduction System

The Cardiac Conduction
System
The Cardiac Conduction System
Definition: Specialized cardiac muscle tissue
with fibers that initiate and distribute impulses
throughout the myocardium.
(muscle layer of the heart)
Purpose: Coordinates the events of the
cardiac cycle
Review: What is the cardiac cycle?
The rhythmic contraction (systole) and
relaxation (diastole) of the chambers of the
heart that corresponds to one heartbeat.
During the cardiac cycle, blood is pumped
out of the heart into the aorta and the
pulmonary artery, and blood reenters the
heart from the venae cavae and the
pulmonary veins.
Link
Parts of the cardiac conduction system
Function of parts
• S-A node- “Pacemaker”
-bundle of cardiac muscle tissue
-sends impulses that cause the atria to
contract
-Passes impulses to the A-V node/A-V
bundle
Did you know the heart can beat outside of the
body because of the S-A node?
Click on the heart to watch.
• A-V node, Junctional fibers, A-V bundle
-slow impulses until atria are done
contracting
-send impulses on to Purkinje fibers
• Purkinje fibers
-Deliver impulses to muscle tissue of
ventricles, causing ventricles to contract
and blood to be forced through pulmonary
artery and aorta
Electrocardiogram (ECG)
• Recording of the electrical changes that
occur in the myocardium during a cardiac
cycle.
When do the
atria relax?
During the
QRS wave.
Relating the cardiac conduction
system to the cardiac cycle
Click on the heart to
watch a video on the
cardiac conduction
system.
Are the cells that create
heart beats part of the
nervous system?
Regulation of the Cardiac Cycle
• One cardiac cycle takes .85 seconds
which results in a heart rate of 70 beats
per minute.
• However, the volume of blood pumped
must change to accommodate cellular
requirements.
-So… although the S-A node can work on
it’s own, the autonomic nervous system
plays a role in the rate of the cardiac cycle.
An example of how the nervous system overrides the cardiac conduction system
What other sensory receptors will the autonomic
nervous system use to monitor and adjust heart
rate?
•Chemoreceptors- can you give an example?
High levels of carbon dioxide increase heart rateWhy? It is a waste product that must be pumped to
the lungs for removal.
•Thermoreceptors- can you give an example?
When the body is overheated the heart beats fasterWhy? To increase the rate at which heat is move
through the body to the surface of the skin for
cooling.
Play the EKG game:
1. The goal of the game is to perform an EKG in
order to diagnose 4 patients heart health.
2. Follow the directions and show your score to your
teacher.
3. Click on the heart to link to the game.