CARDIAC CONDUCTION SYSTEM

Question 1

cardiac conduction system

Answer 1

a system of specialized tissues located in the heart responsible for initiating and distributing nerve impulses to contract cardiac muscle cells.

functions to coordinate the events of the cardiac cycle.

• Heart initiates and distributes nerve impulses to contact its muscle cells through this system of specialized cells
• Stimulation of a fiber sends the signal to one branched fibers

QRS complex blood is being pushed to body or lungs (reason why it is much larger)
- athletes have a stronger qrs complex

Question 2

Structures of the Cardiac Conduction System

Answer 2

Sinoatrial node (S-A node) 
Atrial syncytium 
Junctional fibers 
Atrioventricular node (A-V node)
A-V bundle 
Bundle branches 
Purkinje fibers 
Ventricular syncytium

Question 3

Sinoatrial node (S-A node)

Answer 3

• pace maker

Located in the right atrium near the opening of the superior venacava; just beneath the epicardium. Fibers are continuous with thoseof the atrial syncytium

Question 4

Cardiac impulse

Answer 4

travels from the S-A node into the atrial syncytium (mass of cardiac muscle fibers along the atrial wall) resulting in almost simultaneous contraction of the left and right atria.

The impulse passes along fibers of the conduction system that are continuous with atrial muscle fibers.
These conducting fibers lead to a mass of specialized cardiac muscle tissue called the atrioventricular node (A-V node).

Question 5

Atrioventricular node (A-V node)

Answer 5

• pauses the electrical signal briefly
• we want to make sure the blood is all in the ventricles before it contracts

Located in the inferior portion of the interatrial septum; just beneath the epicardium

functions to slow the spread of impulse to the ventricles

**can also function as a secondary pacemaker if the S-A node should fail. (temporarily only)

Question 6

Junctional fibers

Answer 6

conduct the impulse into the A-V node.

These fibers have very small diameters, therefore, conduction is slow… allowing more time for the atria to completely empty and the ventricles to fill with blood prior to ventricular contraction

Once the impulse reaches the distal side of the A-V node, it passes quickly through a group of large fibers that make up the A-V bundle - Bundle of His.

Question 7

A-V bundle

Answer 7

enters the upper part of the interventricular septum and divides into left and right bundle branches

• goes through branches of the myocardium (speeds up the signal)

Question 8

Purkinje fibers

Answer 8

which spread from the interventricular septum into papillary muscles

( papillary muscles pull on the chordae tendineae when contracting keeping the A-v valves from protruding back into the atria during ventricular contraction)

give off many small branches, which becomes continuous with cardiac muscle fibers

Question 9

Muscle fibers in ventricular walls

Answer 9

occur in irregular whirls - when impulses from Purkinje fibers stimulate them, the ventricular walls contract with a twisting motion.

This action squeezes blood out of the ventricular chambers and into the aorta and pulmonary trunk.