33.3g Cardiac Conductive System

cardiac conductive system

The (?) stimulates the ventricles to depolarize in the proper direction.

superior to inferior, inferior to superior

As mentioned earlier, the atria contract from (?) and the ventricles from (?).

depolarize from superior to inferior

If the depolarization impulse originated in the atria and spread passively to the ventricles, the ventricles would (?) and would be ineffective.

initiate an impulse, spread it through the atria, transmit it quickly to the apex of the heart, stimulate the ventricles to depolarize from inferior to superior

The cardiac conduction system, therefore, must (?), (?), (?), and then (?).

specialized conductive fibers

To do this, the conduction system relies on (?) comprising muscle cells that transmit the depolarization potential through the heart much faster than can regular myocardial cells.

Excitability

(?) is the ability of the cells to respond to an electrical stimulus.

Conductivity

(?) is the ability of cells to propagate an electrical impulse from one cell to another.

Automaticity

(?) is the cardiac pacemaker cells’ capability of self-depolarization.

fastest rate of discharge, or automaticity

Generally, the cell in the cardiac conductive system with the (?) becomes the heart’s pacemaker.

highest cell in the conductive system

As a rule, the (?) has the fastest rate of automaticity.

sinoatrial (SA) node

Normally, this cell is in the (?), high in the right atrium; however, if one pacemaker cell fails to discharge and depolarize, then the cell with the next fastest rate becomes the pacemaker.

Contractility

(?) is the ability of muscle cells to contract, or shorten.

Internodal atrial pathways

(?) connect the SA node to the AV node (Figure 33-16).

depolarization impulse

These internodal pathways conduct the (?) to the atrial muscle mass and through the atria to the AV junction.

AV junction

The (?) (the “gatekeeper”) slows the impulse and allows the ventricles time to fill.

AV node, AV fibers

After the impulse passes through the (?) and on to the (?), the impulse is then conducted to the ventricles.

AV bundle, bundle of His

In the ventricles, the AV fibers form the (?)—also called the (?).

right and left bundle branches

The bundle of His subsequently divides into the (?) and (?).

right bundle branch

The (?) delivers the impulse to the apex of the right ventricle.

Purkinje system

From there, the (?) spreads it across the myocardium.

anterior and posterior fascicles

The left bundle branch divides into (?) that also ultimately terminate in the Purkinje system.

Purkinje system

At the same time that the impulse is transmitted to the right ventricle, the (?) spreads it across the mass of the myocardium.

opposite direction

Repolarization occurs predominantly in the (?).

intrinsic rate of self-excitation

Each component of the conductive system has its own (?).

SA node = 60 - 100 beats per minute

(?).

AV node = 40 - 60 beats per minute

(?).

Purkinje system = 15 - 40 beats per minute

(?).