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Bio 472 > The Heart, Cardiac Muscle Properties, the Electrocardiogram > Flashcards

The Heart, Cardiac Muscle Properties, the Electrocardiogram Flashcards

1
Q

location of the Heart

A

in the Pericardial Sac in the Mediastinal Cavity

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2
Q

Pericardial Sac

A

double walled sac containing the heart and the roots of the great vessels

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3
Q

Mediastinal Cavity

A

central compartment of the thoracic cavity,

surrounded by loose connective tissue

heart, vessels, esophagus, trachea, phrenic and cardiac nerves, thoracic duct, thymus and lymph nodes

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4
Q

Heart Wall parts

A
  1. Epicardium (visceral pericardium)
  2. Myocardium
  3. Endocardium
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5
Q

Epicardium (visceral pericardium)

A

serous membrane that makes up the innermost layer of the pericardial sac and the outermost layer of the heart wall

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6
Q

Myocardium

A

heart muscle, middle layer of the heart wall,

thickest layer of the heart

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7
Q

Endocardium

A

inner layer of the heart wall

similar to epithelial cells

makes up the surface of the valves

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8
Q

4 chambers of the heart

A

2 atria
2 ventricles

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9
Q

What blood enters the right atria?

A

deoxygenated blood from the vena cava

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10
Q

Where does the blood in the right ventricle go to?

A

pulmonary arteries which will take the blood to the lungs

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11
Q

What blood enters the left atria?

A

Oxygenated blood from the lungs/pumonary veins

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12
Q

Where does the blood in the left ventricle go?

A

aorta, which will carry blood throughout the body

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13
Q

Right Side of the Heart

A

deoxygenated blood, low pressure system, pumps blood to the lungs

“Pulmonary Circuit”

tricuspid valve, pulomonary semilunar valve

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14
Q

Left Side of the Heart

A

oxygenated blood, high pressure system, pumps blood to the body

“Systemic Circuit”

bicuspid valve (Mitral Valve), aortic semilunar valve

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15
Q

Cardiac Blood Supply

A
  1. Coronary Arteries(exit from Aorta)
  2. Capillaries
  3. Coronary Veins
  4. Coronary Sinus (outflow into Right Atrium)
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16
Q

Coronary Arteries

A

Branch off from the Aorta into the Left Coronary Artery and Right Coronary Artery

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17
Q

Coronary Veins

A

remove deoxygenated blood from the myocardium

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18
Q

Coronary Sinus

A

largest coronary vein, responsible for venous retuen for 55% of the cardiac blood supply

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19
Q

Cardiac Muscle Structure

A

distinct cells, striated,

Autorhythmicity, “Functional Synctium”

thick and thin filaments, intercalated disks=glue, branched fibers = twist

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20
Q

Autorhythmicity

A

autodepolarization or self-excitable

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21
Q

Functional Syncytium

A

wave of contraction that allows the heart to work as a unit,

breakdown of this causes Fibrillation

thin membranes in between cells, stimulate one cell and they all contract

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22
Q

Atria Autorhythmicity

A

70/min

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23
Q

Ventricle Autorhythmicity

A

20/min

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24
Q

Types of Cardiac Muscle Fibers

A
  1. Fast Response
  2. Slow Response
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25
Q

Fast Response Fibers

A

Atrial and Ventricular Cells

5 phases

-90 to +30 mV, 2 Na+ gates (M gates, H gates)

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26
Q

M Gates

A

activation gates, open for depolarization, allow Na+ entry

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27
Q

H Gates

A

inactivation gates, prevent Na+ entry, closed by end of depolarization

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28
Q

5 Phases of Depolarization in Fast Response Fibers

A
  1. Phase 0
  2. Phase 1
  3. Phase 2
  4. Phase 3
  5. Phase 4
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29
Q

Phase 0 of Depolarization in Fast Response Fibers

A

depolarization, rapid influx of Na+ ions,

Fast Na+ channels

Tetrodotoxin poisons this channel

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30
Q

Phase 1 of Depolarization in Fast Response Fibers

A

Initial repolarization, partial efflux of K+ ions

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31
Q

Phase 2 of Depolarization in Fast Response Fibers

A

plateau phase, Slow Ca++ influx

Ca++ influx is balanced by K+ efflux

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32
Q

Phase 3 of Depolarization in Fast Response Fibers

A

final repolarization, closure of Ca++ channels

large efflux of K+

33
Q

Phase 4 of Depolarization in Fast Response Fibers

A

stabilize resting membrane potential
(Na+/K+ ATPase pump)

34
Q

Effective Refractory Period

A

absolute refractory period

35
Q

Slow Response Fibers

A

higher resting membrane potential (-70 to +10 mV),
unstable membrane potential

no plateau on the depolarization curve

slow depolarization “pacemaker tissue”

36
Q

Phases of Depolarization in Slow Response Tissue

A
  1. Phase 0
  2. Phase 3
  3. Phase 4
37
Q

Phase 0 of Depolarization in Slow Response Tissue

A

action potential spike due to Ca++ influx, some K+ efflux

Tetrodotoxin does not affect it, not steep, not fast Na+ channels,

38
Q

Phase 3 of Depolarization in Slow Response Tissue

A

decrease in Ca++ influx, increase in K+ efflux

repolarizes similar to other excitable tissue

39
Q

Phase 4 of Depolarization in Slow Response Tissue

A

leaky channels, net effect -> Na+, Ca++ influx>K+ efflux, leak to threshold

Na+/K+ ATPase Pump

40
Q

Order of Electrical Flow in the Heart

A
  1. SA Node or pacemaker
  2. AV Node
  3. Bundle of His
  4. Right and Left Bundle Branches
  5. Purkinje Fibers
41
Q

SA Node

A

sinoatrial node, most irritable part of the heart

42
Q

AV Node

A

atrioventricular node

43
Q

3 Standard Bipolar Leads

A

RA, LA, LL

44
Q

3 Augmented Unipolar Leads

A

AVR, AVL, AVF

45
Q

Eintoven’s Triangle

A

triangle around the heart formed by standard bipolar leads and augmented unipolar leads

46
Q

P Wave

A

deerpolarization of the Atria

47
Q

QRS Complex

A

depolarization of ventricles
S marks closure of AV Valves

“Lub” sound

48
Q

T Wave

A

repolarization of the ventricles,

“Dub” sound

same deflection as QRS in most leads, opposite deflection or abnormal height is indicative of myocaridal damage

49
Q

Mean QRS Complex

A

vector sum of bipolar leads or vector sum of unipolar leads

defines a coordinate axis system

50
Q

Finding the Mean QRS Complex

A
  1. look for the most biphasic wave and its corresponding lead, mean QRS will be perpendicular to it
  2. confirm mean QRS direction by looking at two surrounding leads in that SAME LEAD GROUP (either bipolar or unipolar)
  3. mean QRS is their vector sum
51
Q

“Normal” Mean QRS

A

-30 to 100 degrees

60 degrees average

52
Q

Causes Mean QRS to Negative

A

Right Coronary Infarct
Left Ventricular Hypertrophy
Aortic Stenosis
Atherosclerosis

Left side gets bigger or right side gets smaller

53
Q

Causes Mean QRS to Positive

A

Left Coronary Infarct
Right Ventricular Hypertrophy
Pulmonary Emoblus
Pulmonary Contriction

Left side gets smaller or right side gets bigger

54
Q

Right Axis Deviation

A

mean QRS from +100 to +180

55
Q

Left Axis Deviation

A

mean QRS from -30 to -90

56
Q

1 large block on EKG chart paper

A

.20 seconds

57
Q

1 small block on EKG paper

A

.04 seconds

58
Q

Calculating Heart Rate Using an EKG

A

300 dovoded bu the number of large blocks between 2 “R”s

or the # of Rs in 3 seconds times 20

59
Q

Tachycardia

A

heart rate greater than 100 bpm

60
Q

Bradycardia

A

heart rate less than 60 bpm

61
Q

P-R interval

A

0.10-0.20

longer means heart block

62
Q

QRS segment

A

0.10 seconds

62
Q

S

A

closure of AV valves

62
Q

Q-T segment

A

0.40 seconds

62
Q

Heart Blocks

A

Issue with SA to AV

63
Q

1st Degree Heart Block

A

prolonged P-R interval (>0.20 seconds)

usually delay in the AV node

64
Q

2nd Degree Mobitz Type 1(Wenchebach)

A

increasing PR interval, finally P wave does not produce QRS

Longer, longer, longer, drop, now we have a Wenchebach

65
Q

2nd Degree Mobitz Type 2

A

repeating P to QRS ratio of 2:1, 3:1, bradycardia

not all P waves produce QRS deflections

usually problem with conducting through the bundle of His, Pacemaker for treatment

66
Q

3rd Degree Heart Block

A

multiple P waves per QRS AND varying P-R interval,
bradycardia

P waves do not evoke a QRS response, “Complete” Block

slow, regular ventricular rhythm, pacemaker for treatment

67
Q

Paroxysmal Tachycardia

A

abrupt onset and termination of rapid electrical(contractile) events

68
Q

Supraventricular Tachycardia

A

normal QRS except high rate, recurrent AV junction impulse

69
Q

Ventricular Tachycardia

A

huge and wide QRS complexes, aberrant impulse conduction within ventricle

Treat with IV Adenosine, Paced Shock, Vagal Manuevers, Pericardial Thump

Very Dangerous!! Often leads to Ventricular Fibrillation

70
Q

Fibrillation

A

unsynchronized, rippling contractoins

71
Q

Atrial Fibrillation

A

not immedietly life threatening, blood pooling and subsequent clotting is biggest risk

72
Q

Ventricular Fibrillation

A

nearly immediate unconsciousness
lack of cooridinated contraction

little blood pumped

death unless defibrillation occurs

73
Q

Coronary Infarct Indicators

A

multiple events, not visible from all leads, exaggerated Q wave, notched QRS complex, Elevated “ST segment” with “J Point”, inverted T waves with respect to QRS

shift of mean QRS

74
Q

STEMI

A

ST Elevated Myocardial Infartion

75
Q

Inverted T waves

A

Non-Stemi Myocardial infarction

can be normal in small children depending on lead placement

Bio 472 (23 decks)

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