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Perfusion Program Fall 2014 > Conduction system of the heart > Flashcards

Conduction system of the heart Flashcards

1
Q

Name the conduction system in order starting at the top?

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

Cardiac Muscle

A

Elongated, branching cells containing 1-2 centrally located nucl

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3
Q

Cardiac Muscle contains ?

A
  • actin and myosin

myofilaments

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4
Q

Intercalated disks

A

Specialized Cell - Cell contacts

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5
Q

Desmosomes

A

hold cells together

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6
Q

allow action potentials to move from one cell to the next

A

Gap junctions

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7
Q

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

A

Single Unit

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8
Q

Cardiac Mitochondria comprise

A

30% of volume of the cell

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9
Q

Skeletal Mitochondria comprise

A

2 % volume of the cell

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10
Q

Cardiac action potential

A

conducted from cell to cell

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11
Q

Skeletal action potential

A

conducted along the length of a single fiber

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12
Q

Rate of Action Potential Propagation

in CARDIAC muscle?

A

Slow because of gap junctions and small diameter of fibers.

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13
Q

Rate of Action Potential Propagation

in SKELETAL muscle?

A

Faster due to larger diameter fibers.

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14
Q

CICR

A

Calcium-induced calcium release

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15
Q

What stimulates release of Ca2+ from sarcoplasmic reticulum

?

A

Movement of extracellular Ca2+ through plasma membrane and

T tubules into sarcoplasm

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16
Q

Action potential in T-tubule

A

also stimulates Ca++ release from sarco-plasmic reticulum

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17
Q

Rising phase of action potential is due to ?

A

opening of fast Na+ channels

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18
Q

Plateau phase of action potential is due to ?

A 
- Closure of sodium 
   channels
- Opening of calcium
   channels
- Slight increase in K+ 
  permeability
- Prevents summation 
  and thus tetanus of 
  cardiac muscle
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19
Q

Repolarization phase of action potential is due to ?

A
  • Calcium channels
    closed
  • Increased K+
    permeability (K+ out)
20
Q

SA node sends conduction to what 2 structures?

A

AV node

Left Atrium

21
Q

mV =

A

millivolts

22
Q

SA node

A 
The Pacemaker 
- Specialized cardiac 
  muscle cells.
- generate  
  spontaneous action 
  potentials
-
23
Q

AV node

A
  • Action potentials conducted more slowly here than in any other part of system.
  • Ensures ventricles receive signal to contract after atria have contracted
24
Q

passes through hole in cardiac skeleton to reach interventricular septum

A

AV bundle

25
Q

extend beneath endocardium to apices of right and left ventricles

A

Right and left bundle branches

26
Q
  • Large diameter cardiac muscle cells with few myofibrils.
  • Many gap junctions.
  • Conduct action potential to ventricular muscle cells (myocardium)
A

Purkinje fibers

27
Q

Depolarization of SA Node has ?

A

no stable resting membrane potential

28
Q

Pacemaker potential

A

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

29
Q

At what threshold does Action potential

occur?

A

-40 mV

30
Q

depolarizing phase to 0 mV is a result of what ?

A

fast Ca2+ channels open, (Ca2+ in)

31
Q

repolarizing phase is a result of what ?

A 
- K+ channels open, 
  (K+ out)
- at -60 mV K+ 
  channels close, 
  pacemaker potential 
  starts over
32
Q

Each depolarization creates

A

1 hearbeat

33
Q

SA node at rest fires at 0.8 sec, about

A

75 bpm

34
Q

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

A

75 times/minute

35
Q

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

A

delays the impulse approximately 0.1 second

36
Q

Impulse passes from atria to ventricles via the

A

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

37
Q

depolarization of atrial myocardium.

Signals onset of atrial contraction

A

P wave

38
Q

Ventricular depolarization

A

QRS Complex

39
Q

Repolarization of the ventricles

A

T wave

40
Q

length of time for the PR interval or PQ interval?

A

0.16 sec

41
Q

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

A

Damage to the conducting pathway or AV node has occurred

42
Q

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

A

Q-T interval

43
Q

What can lengthen Q-T interval ?

A
  • electrolyte disturbances
  • conduction problems
  • coronary ischemia
  • myocardial damage
44
Q

Internodal pathways are located in the ?

A

RA

45
Q

Conduction System pathway from SA - AV in milliseconds?

A

.03 msec

46
Q

Conduction System pathway from AV - Bundle branch in milliseconds?

A

.17 msec

47
Q

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

A

.21 msec

Perfusion Program Fall 2014 (14 decks)

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