Conduction system of the heart

Question 1

Heart () and contracts without nervous system stimulation, although rhythm can be altered by autonomic nervous system

Answer 1

depolarizes

Question 2

Coordinated heartbeat is a function of:
Presence of gap junctions (intercalated discs b/w muscle fibers)

() cardiac conduction system
-Network of non-contractile (autorhythmic) cells
-Initiate and distribute impulses to coordinate depolarization and contraction of heart

Answer 2

Intrinsic

Question 3

Sequence of ()
Cardiac pacemaker cells pass impulses, in following order, across heart in ~0.22 seconds

() node →
() node → Bundle of () → Right and left bundle () →
() fibers

Answer 3

excitation
Sinoatrial
Atrioventricular
His
branches
Purkinje

Question 4

() (SA) node
() of heart in right atrial wall
Generates impulses about 60-100/minute (sinus rhythm)
Impulse spreads across atria, and to AV node

Answer 4

Sinoatrial
Pacemaker

Question 5

() (AV) node
In inferior () septum
Delays impulses approximately 0.1 second
Allows atrial contraction prior to ventricular contraction

Answer 5

Atrioventricular
interatrial

Question 6

Atrioventricular (AV) () (bundle of His)
In () interventricular septum
Only electrical connection between atria and ventricles

Answer 6

bundle
superior

Question 7

Right and left bundle ()
-Two pathways in interventricular septum
-Carry impulses toward apex of heart

Answer 7

branches

Question 8

() Fibers
Through interventricular septum into apex and ventricular walls
More elaborate on () side of heart

Answer 8

Purkinje
left

Question 9

Defects in intrinsic conduction system may cause:
(): irregular heart rhythms
Uncoordinated atrial and ventricular contractions

Answer 9

Arrhythmias

Question 10

Defects in intrinsic conduction system may cause:
(): rapid, irregular contractions

Heart becomes useless for pumping blood, causing circulation to cease; may result in brain death

Treatment: defibrillation interrupts chaotic twitching, giving heart “clean slate” to start regular, normal depolarizations

() fibrillation: more manageable and common
() fibrillation: serious and life-threatening

Answer 10

Fibrillation
Atrial
Ventricular

Question 11

To reach ventricles, impulse must pass through () node
-If AV node is defective, may cause a heart ()

Answer 11

AV
block