CV III Flashcards
What is the conducting system of the heart
SA node - internodal pathways - AV node - AV bundle - left and right bundle branches - purkunje fibers
What is the bundle of His
AV bundle
What part of the conducting system passes into the ventricles
AV bundle/bundle of His
What are the 4 special conducting bundles
Backman’s bundle
Anterior, middle, posterior internodal pathways
What does the backman’s bundle do
Conducts APs front the SA pacemaker into the LA causing contraction
What do the anterior, middle, and posterior internodal pathways do
Conduct AP from SA node to AV node, depolarizing right atrial muscle along way
What is speed of atrial conduction
Relatively Slow
80-100ms
What prevents conduction directly from atria to ventricle
Layer of connective tissue
Why does conduction slow through AV node
Allows blood from atria to empty into ventricles, allows atrial contraction to pump little more blood in
What way does depolarization spread through heart
Through septum to apex then up the walls of ventricles from apex to base
What is speed of ventricular contraction
More rapid
60–100ms
How are ventricular muscles arranged and what does it ensure
Spiral arrangement
Ensures blood is squeezed upward from apex of heart
What is ventricular muscle attached to
Insertion and origin on AV ring
Start and come around to attach to AV ring on other side
What happens if electrical activity cannot be transferred from atria to ventricles (damage to AV bundle)
Complete conduction block
SA node continues as pacemaker for atria
Purkinje fibers must take over as pacemaker for ventricles but much slower
Requires artificial pacemaker
What does electrocardiography (ECG, EKG) measure
Records summed electrical activity generated by all cells of the heart
How is electrocardiogram work
Salt solutions lie NaCl based ECF are good conductors of electricity
What is Einthoven’s triangle
Triangle created around heart
Electrodes pairs attached to both arms and one leg
What are leads
Pairs of electrodes
How is ECG recorded using triangle
One electrode acts as positive and one negative
How many leads in modern ECG
12
Electrical activity of heart moving towards positive electrode
Upward deflection is recorded
Electrical activity moving away from positive electrode
Recorded as downward deflection
A vector moving perpendicular to axis of electrodes
Causes no deflection
What are ECGs a combination of
Waves and segments
