Conduction system of the heart

Question 1

Name the conduction system in order starting at the top?

Answer 1

1. ) Sinus Node
2. ) AV Node
3. ) AV bundle
4. ) Left & Right bundle branch
5. ) Purkinje Fibers

Question 2

Cardiac Muscle

Answer 2

Elongated, branching cells containing 1-2 centrally located nucl

Question 3

Cardiac Muscle contains ?

Answer 3

• actin and myosin

myofilaments

Question 4

Intercalated disks

Answer 4

Specialized Cell - Cell contacts

Question 5

Desmosomes

Answer 5

hold cells together

Question 6

allow action potentials to move from one cell to the next

Answer 6

Gap junctions

Question 7

Electrically, cardiac muscle of the atria and of the ventricles behave as ?

Answer 7

Single Unit

Question 8

Cardiac Mitochondria comprise

Answer 8

30% of volume of the cell

Question 9

Skeletal Mitochondria comprise

Answer 9

2 % volume of the cell

Question 10

Cardiac action potential

Answer 10

conducted from cell to cell

Question 11

Skeletal action potential

Answer 11

conducted along the length of a single fiber

Question 12

Rate of Action Potential Propagation

in CARDIAC muscle?

Answer 12

Slow because of gap junctions and small diameter of fibers.

Question 13

Rate of Action Potential Propagation

in SKELETAL muscle?

Answer 13

Faster due to larger diameter fibers.

Question 14

CICR

Answer 14

Calcium-induced calcium release

Question 15

What stimulates release of Ca2+ from sarcoplasmic reticulum

?

Answer 15

Movement of extracellular Ca2+ through plasma membrane and

T tubules into sarcoplasm

Question 16

Action potential in T-tubule

Answer 16

also stimulates Ca++ release from sarco-plasmic reticulum

Question 17

Rising phase of action potential is due to ?

Answer 17

opening of fast Na+ channels

Question 18

Plateau phase of action potential is due to ?

Answer 18

- Closure of sodium 
   channels
- Opening of calcium
   channels
- Slight increase in K+ 
  permeability
- Prevents summation 
  and thus tetanus of 
  cardiac muscle

Question 19

Repolarization phase of action potential is due to ?

Answer 19

• Calcium channels
  closed
• Increased K+
  permeability (K+ out)

Question 20

SA node sends conduction to what 2 structures?

Answer 20

AV node

Left Atrium

Question 21

mV =

Answer 21

millivolts

Question 22

SA node

Answer 22

The Pacemaker 
- Specialized cardiac 
  muscle cells.
- generate  
  spontaneous action 
  potentials
-

Question 23

AV node

Answer 23

• Action potentials conducted more slowly here than in any other part of system.
• Ensures ventricles receive signal to contract after atria have contracted

Question 24

passes through hole in cardiac skeleton to reach interventricular septum

Answer 24

AV bundle

Question 25

extend beneath endocardium to apices of right and left ventricles

Answer 25

Right and left bundle branches

Question 26

- Large diameter cardiac muscle cells with few myofibrils. - Many gap junctions. - Conduct action potential to ventricular muscle cells (myocardium)

Answer 26

Purkinje fibers

Question 27

Depolarization of SA Node has ?

Answer 27

no stable resting membrane potential

Question 28

Pacemaker potential

Answer 28

gradual depolarization from -60 mV, slow influx of Na+

Question 29

At what threshold does Action potential | occur?

Answer 29

-40 mV

Question 30

depolarizing phase to 0 mV is a result of what ?

Answer 30

fast Ca2+ channels open, (Ca2+ in)

Question 31

repolarizing phase is a result of what ?

Answer 31

``` - K+ channels open, (K+ out) - at -60 mV K+ channels close, pacemaker potential starts over ```

Question 32

Each depolarization creates

Answer 32

1 hearbeat

Question 33

SA node at rest fires at 0.8 sec, about

Answer 33

75 bpm

Question 34

In the Sequence of Excitation, the Sinoatrial (SA) node generates impulses about _____

Answer 34

75 times/minute

Question 35

In the Sequence of Excitation, the Atrioventricular (AV) node

Answer 35

delays the impulse approximately 0.1 second

Question 36

Impulse passes from atria to ventricles via the

Answer 36

> AV bundle (Bundle of His) > Purkinje Fibers > Myocardial fibers

Question 37

depolarization of atrial myocardium. | Signals onset of atrial contraction

Answer 37

P wave

Question 38

Ventricular depolarization

Answer 38

QRS Complex

Question 39

Repolarization of the ventricles

Answer 39

T wave

Question 40

length of time for the PR interval or PQ interval?

Answer 40

0.16 sec

Question 41

a PR interval or PQ interval > than 0.20 sec (200 msec) indicates what ?

Answer 41

Damage to the conducting pathway or AV node has occurred

Question 42

time required for ventricles to undergo a single cycle of depolarization and repolarization

Answer 42

Q-T interval

Question 43

What can lengthen Q-T interval ?

Answer 43

- electrolyte disturbances - conduction problems - coronary ischemia - myocardial damage

Question 44

Internodal pathways are located in the ?

Answer 44

RA

Question 45

Conduction System pathway from SA - AV in milliseconds?

Answer 45

.03 msec

Question 46

Conduction System pathway from AV - Bundle branch in milliseconds?

Answer 46

.17 msec

Question 47

Conduction System pathway from bundle branch - purkinje fibers in milliseconds?

Answer 47

.21 msec