Identify the component of the heart’s electrical conduction system that fits each description below: Establishes the basic heartrate: Delays action potential, letting the atria and ventricles contract...

Identify the component of the heart’s electrical conduction system that fits each description below:

1. 
   
   Establishes the basic heartrate:


2. 
   Delays action potential, letting the atria and ventricles contract separately:
   


3. 
   Conduct action potential through interventricular septum:
   


4. 
   Directly brings action potential to contractile cells of the heart: