17.5 Chapter Human Structure and Function

Autorhythmic cells

have special ability to depolarize

Intrinsic cardiac conduction system

non-contractile cardiac cells specialized to initiate and distribute impulses throughout heart, allows depolarization and contraction in correct manner

Cardiac pacemaker cells

Have ability to depolarize to pace the heart

Sinoatrial node/ SA node

In right atrial wall, sets pace for heart as a whole, fastest depolarization rate

Sinus rhythm

Rhythm of SA node that determines heart rate

Atrioventricular node/ AV node

In inferior interatrial septum, Depolarization from SA node moves by gap junctions to AV node, Impulse is delayed allowing atria to respond and complete their contraction before the ventricles contract

Atrioventricular bundle/ AV bundle

Impulse moves from AV node to AV bundle, in superior interventricular septum, AV bundle only electrical connection between atria and ventricles

Cardioacceleratory center

In medulla, sends signals to sympathetic branch, speed up by SA node

Cardioinhibitory center

In medulla, sends signals to parasympathetic branch, slowed down by SA node

Electrocardiogram (ECG)

graphical recording of heart activity

Electrical depolarization

leads to cardiac muscle contraction

Electrical repolarization

leads to cardiac muscle relaxation

P wave

first, atrial depolarization inited by SA node

QRS complex

After delay post P wave from atrial depolarization ending, largest wave caused by ventricular depolarization

T wave

After delay post QRS complex from ventricular depolarization ending, T wave caused by ventricular repolarization