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Blake_Physiology_Test 2 > Blake_Physio_07_Heart Rhythmicity > Flashcards

Blake_Physio_07_Heart Rhythmicity Flashcards

1
Q

SA node: definition, loccation and connections

A

Sinoatrial Node
Special Cardiac Muscle Fibers
SA fibers connect directly to atrial fibers

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2
Q

AV node: definition
Receives signal ______ sec after origin
Signal is delayed in AV node for ________ sec
final delay of ____ sec in penetrating bundles
=> there is a ____sec delay from the initial origin of the isgnal until the onset of ventricular contraction

A

Atrioventricular Node

  1. 03
  2. 09
  3. 04
  4. 16
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3
Q

Why is signal delayed in the AV node for 0.09 sec?

A

Due to the small size of cells, low amplitude of AP, and slow rate of depolarization during excitation.

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4
Q

CONDUCTIVE SYSTEM OF THE HEART:
Slow conduction is caused mainly by diminished numbers of _____________ along the pathway resulting in an _____________ in the __________ to ___________

A

Gap junctions
increase
resisitance
conduction

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5
Q

Resting membrane potential of SA node fiber:

A

-55 to -60mV (threshhold~-40mV)

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6
Q

At resting potential, the Fast sodium channels in the SA node are____________

A

inactivated

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7
Q

Inactivation gates close when the membrane potential of the SA node is __________________.

As a result, only ______ ______-_____ channels can open.

THEREFORE: (2 things)

A

less than -55mV

slow sodium-calcium

  • atrial nodal AP is slower to develop
  • repolarization is slower
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8
Q

What causes the SA node to reach threshold on its own?

A

slow leak of sodium Ions back into cells

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9
Q

Sodium-calcium channels in the SA node are inactivated within _____ to _______ msec after opening

A

100-150

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10
Q

Resting membrane potential of SA node fiber:
Large numbers of _________ channels open at the time the __________-________ channels become ________

Nodal cells become ____________

Potassium channels remain __________ for a few tenths of a second

A

potasium, sodium-calcium, inactivated

repolarized

open

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11
Q

Ventricular fiber resting potential:

A

=85 to -90mV

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12
Q

Sinus Rhythm

A

AP originating in the SA node

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13
Q

Action potentials that originate anywhere other than the SA node are said to be from an ________ or ________

A

ectopic focus or pacemaker

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14
Q

What parasympathetic nerve can modulate heart rate?

What result does parasympathetic innervation have on the heart?

A

Vagus nerve

Decreased heart rate

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15
Q

What receptors does acetylcholine affect on the heart?

A
  • Muscarinic receptors on the SA and AV nodes
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16
Q

What effect does acetylcholine have on the SA node?

A

decreases rate of rhythm (negative chronotropic effect)

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17
Q

What effect does acetylcholine have on the AV node?

A

Decreases excitability of the AV junctional fibers, slowing transmission of the cardiac impulse into the ventricles.

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18
Q

How does acytlycholine generally accomplish it’s functions in cardiac tissues? (2 things)

A
  • Increases permeability of fiber membranes to potassium ions
  • Hyperpolarization: -65 to -70mV
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19
Q

How does sympathetic innervation by norepiniphrine effect cardiac tissue? (3 things)

A
  • stimulates beta-1 adrenergic receptors
  • increases depolarization rate (positive chronotropic effect)
  • may increase permeability of fiber membranes to sodium and calcium ions
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20
Q

Where is norepinephrine distributed to the heart by sympathetic nerves?

A

All parts of the heart, mainly the ventricles.

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21
Q

In an ECG Depolarization is represented by the_ _ _

A

P and QRS waves

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22
Q

ECG: P wave represents

QRS wave represents

T wave represents

A

Atrial depolarization

Ventricular depolarization

Ventricular repolarization

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23
Q

In an ECG, why is there no wave representing Atrial repolarization?

A

because it is obscured by the QRS wave

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24
Q

An ECG measures ______________

A

Extracellular potential

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25
Q

Deflection from 0 occurs only when there is __________ between regions of the heart. Current flows between ________ of different _____________.

A

current flow
regions
membrane potentials

26
Q

Because atrial musculature and ventricular musculature are _________ _________, current flow does not occur when only the ________ and the _______ have different _______.

A

electrically isolated
atria
ventricals
potentials

27
Q

Monophasic action potential of the ventricular muscle:

A

Depolarization and Repolarization both register as positive.

28
Q

in an ECG, no potential is recorded when the ventrical is:

A

completely polarized

completely depolarized

29
Q

Normal ECG: P wave occurs at the beginning of the contraction of the ______. QRS complex occurs at the beginning of the contraction of the __________. Repolarization of the _______ occurs after the end of the _______.

A

atria
ventricals
ventricals
T-wave

30
Q

how long is the P-Q interval?

A

0.16 sec

31
Q

How long is the Q-T interval?

A

0.35 sec

32
Q

Three bipolar limb leads:
I
II
III

A

I - neg to R-arm; pos to L-arm; Left to Right
II - neg to R-arm; pos to L-leg; upper right to lower left
III - neg to L-arm; pos to L-leg; upper left to lower left

33
Q

Two arms and left leg form ________ triangle

A

Einthoven’s

34
Q

Einthoven’s law:

A

If the electrical potentials of any two of the three bipolar limb leads are known at any givan instant, the third can be determined by summing the first two.

35
Q

Normally, in the ventricals, current flows from ______ to the ________ in the direction of the _______ of the heart to the _________ for most of the heart cycle until the very end.

A

negative to positive

base to apex

36
Q

Axis for ECG bipolar limb leads:
I
II
III

A

I - 0
II - 60
III - 120

37
Q

The QRS vector: name and angle

A

mean electrical axis

59 degrees

38
Q

T-Wave:
Greatest portion of ventricular mass to repolarize first is the entire_____________ of the _________, especially near the _________.

A

outer surface
ventricles
apex

39
Q

T-Wave:

Endo cardial areas normally repolarize ________

A

last

40
Q

T-wave:

Ventricular vector during repolarization is toward the ______ of the _________

A

apex of the heart

41
Q

T-wave:

Normal T-wave in all three bipolar leads is ________

A

positive

42
Q

P-wave:

Atrial depolarization begins in the ________

A

Sinus Node

43
Q

P-wave:

Vector direction is generally in the ________of the axes of the three standard bipolar limb leads.

A

same direction

44
Q

P-wave:

ECG of P-wave is normally _______ in all three leads

A

positive

45
Q

Atrial T-wave:

Spread of depolarization through atrial muscle is ________ than in ____________

A

slower than in ventricles

46
Q

Atrial T-wave:
Musculature around the sinus node becomes __________ a long time _______ the musculature in the distal parts of the atria.

A

depolarized

before

47
Q

Atrial T-wave:

The ___________ area is the first part to become repolarized.

A

sinus node

48
Q

Atrial T-wave:

At the beginning of repolarization, the sinus node is ___________ with respect to the rest of the atria.

A

positive

49
Q

Atrial T-wave:

Atrial T-wave is almost always ________ by the QRS wave.

A

obscured

50
Q

A typical ECG may utilize ___ leads.

Each lead provides a _______ _______ on the _____ _________ between areas of the heart.

In addition to the three bipolar (conventional leads) there are:

A

12

different perspective
voltage difference

6 standard leads (V1-V6)
Three augmented Leads (aVR, aVL, aVF)

51
Q

The mean electrical axis is the direction of _________________ from the __________ to the _______

A

electrical potential

base of the ventricals to the apex

52
Q

5 abnormal ventricular conditions that cause axis deviation:

A
  • Change in position of the heart in the chest
  • hypertrophy of one ventrical
  • bundle branch block
  • fluid in pericardium
  • pulmonary emphysema
53
Q

Abnormal Voltages of QRS complex:
In creased voltage in the standard bipolar leads: (2 things)

(1 measurement, 1 cause)

A
  • High-voltage ECG is said to occur when the sum of the voltages of all QRS complexes of the three standard leads is greater than 4mV.
  • Most common cause is hypertrophy of the ventricle.
54
Q

Abnormal Voltages of QRS complex:

Decreased Voltage: (2 causes)

A

cardiac myopathies

conditions surrounding the heart

55
Q

Hypertrophy or dilation of the left or right ventricle, QRS may be prolonged to _____ to _____ sec

A

0.09 to 0.12 sec

56
Q

Conditions causing bizarre QRS complexes:

A
  • Destruction of cardiac muscle and replacement by scar tissue.
  • Multiple small local blocks in the conduction impulses at many points in the Purkinje system.
57
Q

Currents of injury:

Different cardiac abnormalities cause part of the heart to remain ________ or _______ ______ all the time

A

partially or totally depolarized

58
Q

_______ of ______ flows between the pathologically depolarized and the normally polarized areas, even between heart beats.

A

current of injury

59
Q

Abnormalities causing current of injury: (3)

A

Mechanical Trauma
Infectious Processes
Ischemia (most common)

60
Q

Effect of current of injury on QRS complex:

A

Abnormal negative current flows from infarcted area and spreads toward the rest of the ventricles.

61
Q

J point =

A

reference point on ECG for analyzing current of injury.

Blake_Physiology_Test 2 (6 decks)

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