The Human Heart

What are 3 types of tissue in the heart?

1) Nervous Tissue

2) Muscle Tissue

3) Fibrous Tissue (non-conductive)

The cardiac conduction system is formed by what type of tissue?

Nervous tissue

Functions of cardiac muscle tissue?

• contracts/ pumps blood

• conducts signal (slow)

  • that’s why we need the cardiac conduction system to conduct the signals very quickly

3 function of fibrous tissue in the heart?

• forms cardiac skeleton

• anchors heart valves

• separates atria from ventricles: prevents them from mixing electrically and mechanically

  • important: we don’t want atria and ventricles contracting at the same time

  • only way signal can pass through here is via the cardiac conduction system

What are the two sections separated by fibrous tissue called?

• atrial syncytium

• ventricular syncytium

What is a syncytium?

• syncytium: group of cells electrically connected to each other

• e.g. all of the cardiac muscle in the atrial syncytium are connected electrically, so if one cell depolarizes it depolarizes the next cardiac muscle cell and so on until entire atrial syncytium depolarizes

Image of heart (types of tissue)

What are the 2 nodes and where are they located?

1) Sinoatrial (SA) node (top of right atrium)

2) Atrioventricular (AV) node (bottom of right atrium)

Which node is the pacemaker of the heart?

• autorhythmic, generates own electrical impulses setting heart’s normal rhythm

• can be regulated by brain but doesn’t need that input to send signals and maintain a rhythm aka autorhythmic 

What is the pathway of the Cardiac Conduction System?

1) Signal generated in SA node

2) Travels to AV node (delays the signal)

3) Travels through the bundle of His 

4) Goes down left and right bundle branches

5) going through the Purkinje fibers

What is the delay of signal by AV node important?

gives a chance for the atria to fully contract before ventricles

Importance of Purkinje fibers?

it spreads the signal through the muscle of the right and left ventricles

In which step of the conduction pathway do the ventricles contract?

when the signal moves up the bundle branches from the sides, this allows for a good solid contraction to occur from the apex of the heart

Image of Conduction system of heart