conducting system of the heart

long __ period prevents tetanic contractions

long refractory period prevents tetanic contractions

1. action potentials originate in the __ (SA) node (the pacemaker) and travel across the wall of the atrium (arrows) from the SA node to the __ (AV) node

1. action potentials originate in the sinoatrial (SA) node (the pacemaker) and travel across the wall of the atrium (arrows) from the SA node to the atrioventricular (AV) node

2. action potentials pass through the AV node and along the AV __, which extends from the AV node, through the fibrous skeleton, into the __ __

2. action potentials pass through the AV node and along the AV bundle, which extends from the AV node, through the fibrous skeleton, into the interventricular septum

3. the AV bundle divides into right and left bundle branches, and action potentials descend to the __ of each ventricle along the bundle branches

3. the AV bundle divides into right and left bundle branches, and action potentials descend to the apex of each ventricle along the bundle branches

4. action potentials are carried by the Purkinje fibers from the bundle branches to the __ walls and __ muscles

4. action potentials are carried by the Purkinje fibers from the bundle branches to the ventricular walls and papillary muscles

__ __: passes through hole in cardiac skeleton to reach interventricular septum

AV bundle: passes through hole in cardiac skeleton to reach interventricular septum

AV node: __ node

AV node: atrioventricular node

__ __: Medial to the right atrioventricular valve. action potentials conducted more slowly here than in any other part of system. ensures ventricles receive signal to contract after atria have contracted

AV node: atrioventricular node. Medial to the right atrioventricular valve. action potentials conducted more slowly here than in any other part of system. ensures ventricles receive signal to contract after atria have contracted

__ __: large diameter cardiac muscle cells with few myofibrils. many gap junctions. conduct action potential to ventricular muscle cells

Purkinje fibers: large diameter cardiac muscle cells with few myofibrils. many gap junctions. conduct action potential to ventricular muscle cells

__ __: medial to opening of superior vena cava. he pacemaker. specialized cardiac muscle cells. generate spontaneous action potentials. action potentials pass to atrial muscle cells and to the __ node.

SA node: medial to opening of superior vena cava. he pacemaker. specialized cardiac muscle cells. generate spontaneous action potentials. action potentials pass to atrial muscle cells and to the AV node.

SA node: __ node

SA node: sinoatrial node

__ period: cardiac muscle cell completely insensitive to further stimulation

absolute period: cardiac muscle cell completely insensitive to further stimulation

__ period: cell exhibits reduced sensitivity to additional stimulation

relative period: cell exhibits reduced sensitivity to additional stimulation

right and left bundle branches: extend beneath __ to apices of right and left __

right and left bundle branches: extend beneath endocardium to apices of right and left ventricles

the heartbeat is controlled externally by a cardiac center in the brain and hormones such as epinephrine, norepinephrine, and __

the heartbeat is controlled externally by a cardiac center in the brain and hormones such as epinephrine, norepinephrine, and acetylcholine