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ECG > Intro and Electophysiology > Flashcards

Intro and Electophysiology Flashcards

1
Q

outer fibrous layer of pericardial sac is called

A

Parietal Pericardium

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2
Q

inner fibrous layer of pericardial sac is called

A

Visceral Pericardium

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3
Q

What is the name of the tough fibrous sac that encloses the heart

A

the pericardial sac

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4
Q

what lubricates the visceral and parietal pericardium

A

pericardial fluid

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5
Q

Name and describe the 3 layers of the heart wall

A
  1. Epicardium: a thin serous membrane on the outer aspect of the heart
  2. Myocardium: a muscular middle layer of the heart
  3. Endocardium: a thin serous membrane lining the inner chambers of the heart
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6
Q

What are the two basic cell types of the heart?

A

Myocardial cells and Conducting cells

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7
Q

What are the “working cells” of the heart?

A

myocardial cells, they have contractile ability

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8
Q

What is a syncytium?

A

the branching network of myocardial cells which consist of latticework of protein filaments (actin and myosin)

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9
Q

Name the types of conducting cells

A
  • pacemaker cells

- electrical conducting cells (bundle branches and Purkinje fibers)

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10
Q

Describe cardiomyocytes

A

branching cells with a central nucleus, surrounded by a sarcolemma

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11
Q

Sarcolemma

A

membrane surrounding cardiomyocytes

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12
Q

Intercalcated disks

A

special contact points where the cells connect

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13
Q

Gap junctions (location and function)

A

gap junctions are located in the intercalcated disks and permit rapid conduction of electrical impulses from one cell to the next

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14
Q

Desmosomes (function)

A

hold myocardial cells together during contraction

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15
Q

When stimulated, do myocytes contract together or separately?

A

Myocytes contract together as a single unit during contraction

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16
Q

What is the cardiac skeleton?
What is its function?
Why is it good to have?

A

1- a “plate of fibrous connective tissue” between the atria and ventricles
2- provides a support structure for the AV and semilunar valves and separates the upper pumping chambers from the lower pumping chambers
3- Electrically insulates the atria from the ventricles. Electrical impulses in the atria must travel through specific conduction pathways to get to the ventricles.

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17
Q

What is systole?

A

contraction phase

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18
Q

What is diastole?

A

relaxation phase

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19
Q

Stroke volume (def and normal values)

A
  • amount of blood ejected from ventricles during systole

- usually 60-100 cc of blood ejected into circulation during systole

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20
Q

How does one calculate cardiac output?

A

Heart rate x Stroke volume= Cardiac output

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21
Q

Preload

A

stretching force on the ventricular muscle at end diastole

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22
Q

Afterload

A

pressure against which the heart must pump (e.g. blood pressure in the aorta)

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23
Q

Blood Pressure=

A

Blood Pressure = Cardiac Output x Peripheral Vascular Resistance

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24
Q

By what means in the heart regulated?

A

The Brain via autonomic nervous system
Hormones of the endocrine system
Heart tissue
Receptors monitoring adequacy of cardiac output. Located in: blood vessels, kidneys, brain, heart

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25
Q

Baroreceptors (functiona and location)

A

Baroreceptors detect changes in pressure in the heart and main arteries (aorta and carotid arteries)

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26
Q

Chemoreceptors

A

detect changes in the chemical composition of the blood

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27
Q

Where does info from baroreceptors and chemoreceptors go?

A

info from baroreceptors and chemoreceptors is transmitted to the cardioregulatory center in the medulla oblongata

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28
Q

What is the “adrenergic system”

A

the sympathetic nervous system

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29
Q

What does the sympathetic nervous system do?

A
  1. causes release or norepinepherine and epinepherine (from adrenal glands)
  2. Flight or Flight response
    speeds heart; increases myocardial excitability

-“Cardioaccelerator”: increased pacemaker firing, increased impulse conduction through heart, increased force of contraction, coronary vasodilation

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30
Q

How are cardioaccelerator effects caused and what are the effects?

A

sympathetic system activates beta receptors ->cardioaccelerator effects

  1. increased rate of pacemaker firing
  2. increased spread of impulse conduction through heart
  3. increased force of contraction
  4. coronary vasodilation
31
Q

Parasympathetic nervous system:

how is it activated? what does it do?

A

Vagus nerve stimulates release of acetylcholine
aka. “cholinergic system”
slows heart and slows electrical conduction
“cartdioinhibitor”: decreased rt of SA node pacemaker, decreased rate of condutction through AV node

32
Q

What does the cardioregulatory center do when blood pressure is too low?

A

Cardioregulatory center activates sympathetic nervous system which:

  • causes release of epinepherine and norepinepherine
  • increases heart rate and contractility
  • constricts peripheral blood vessels
  • > results in increased cardiac output and increased blood presure
33
Q

Name and describe 4 key properties of myocardial cells

A

Automaticity: certain cells can produce an electrical impuse without outside nervous stimulation
Excitability: ability to respond to an electrical stimulus
Conductivity: ability to transmit an electrical stiumul from cell to cell
Contractility: ability to contract when electrically stimulated

34
Q

The Conductive Pathway

A

specialized cardiac cells that generate and transmit electrical impulses throughout the myocardium

35
Q

name 2 types of cells in the conductive pathway; what do they do?

A
  1. Pacemaker cells-have the ability to spontaneously generate an impulse (“depolarize”) at a certain rate
  2. Electrical conducting cells: carry the electrical impulses to the appropriate regions of the heart
36
Q

Sinoatrial (SA) node

A

the heart’s primary pacemaker
located high in POSTERIOR RIGHT ATRIUM
intrinsic rate is 60-100 bpm

37
Q

Atriventricular (AV) Node

A

pathway for impulses to reach the ventricles
located in LOW RIGHT ATRIUM
intrinsic rate is 40-60 bpm
acts as a GATEKEEPER for impulses reaching the ventricles; conducts impulses more slowly

38
Q

Bundle of His

A

aka AV Bundle; transmits signal from AV node to heart apex

39
Q

Right and Left bundle branches

A

located on either side of interventricular septum

Left Bundle branches into anterior and posterior fascicles

40
Q

Purkinje fibers

A

terminal branches of the right and left bundles that spread out through the myocardium

41
Q

What is the intrinsic rate of Purkinje fibers

A

20-40 bpm, will take over as pacemaker if SA and AV nodes fail

42
Q

What takes over as a pacemaker if the SA and AV nodes fail?

A

Purkinje fibers

43
Q

Intrinsic rate of SA node

A

60-100 bpm

44
Q

Intrinsic rate of AV node

A

40-60 bpm

45
Q

Polarized State of myocardial cells

A

resting state; consists of
NEGATIVELY charged ions INSIDE cell and
POSITIVELY charged ions OUTSIDE cell

46
Q

Resting Membrane Potetion

A

the difference in electrical charge between inside and outside the cell

47
Q

What occurs during DEpolarization?

A

positive ions (Na+) enter the cell, causing interior to become positively charged or “depolarized”; calcium ions also enter, but more slowly

48
Q

Action potential of cell

A

the change in electrical charge over time

aka Voltage of the cell

49
Q

What occurs during REpolarization?

A

after cell is depoloarized, the positive ions (Na+, Ca++. K+) leave the cell and the interior of the cell returns to its negatively charged resting state

50
Q

Absolute refractory period definition and 2 impacts

A

following depolarization, cell becomes temporarily resistant to further depolarization

  1. this keeps the wave of depolarization moving forward
  2. also prevents spasms of continued contraction in one area
51
Q

Relative refractory period

A

In late phase of repolarization, a very strong electrical stimulus will cause depolarization

52
Q

Who invented the first practical ECG? When? Did he receive any accolades?

A

William Einthoven (Dutch physician and physiologist) invented ECG in 1903 and received a Nobel Prize in Medicine in 1924 for this masterpeice

53
Q

Bipolar leads (definition and which ones)

A

bipolar leads have electrodes of opposite polarity (positive and negative)
-The limb leads- leads I, II, and III are BIPOLAR

54
Q

Unipolar leads (definition and which ones)

A

have only a positive electrode and a reference point determined by the ECG machine
-the chest/precordial leads (V1-V6), the augmented limb leads

55
Q

How does movement toward a positive electrode appear on ECG?

A

movement toward a positive electrode appears above baseline (upright) on the ECG

56
Q

How does movement away from a positive (toward a negative) electrode appear on ECG?

A

appears below a baseline

57
Q

What is a vector?

A

small directional electrical currents

58
Q

What is an electrical axis?

A

the overall direction of the sum of currents (or vectors)

59
Q

What produces downward deflections on ECG?

A

impulses travelling away from a positive electrode and/or toward a negative electrode

60
Q

What produces upward deflections on ECG

A

Impulses travelling toward a positive electrode

61
Q

What produces a biphasic waveform on ECG?

A

impulses travelling perpendicular to the positive elctrode

62
Q

What is a biphasic waveform?

A

one that has both a positive and negative deflection

63
Q

Which leads are on the frontal plane

A

limb leads I, II, III, aVR, aVF

64
Q

Which leads are on the horizontal plane

A

precordial (chest) leads V1 to V6

65
Q

Which wave represents atrial depolarization?

A

P wave

66
Q

What does the QRS wave represent?

A

ventricular depolarization

67
Q

Which wave represents ventricular repolarization?

A

T wave

68
Q

Which wave represents atrial repolarization?

A

none, it is hidden in the QRS wave

69
Q

Which wave represents ventricular depolarization?

A

QRS wave

70
Q

What does the P wave represent?

A

atrial depolarization

71
Q

What does the T wave represent?

A

ventricular depolarization

72
Q

Epicardium:

A

thin serous membrane on the outer aspect of the heart

73
Q

Myocardium

A

muscular middle layer of the heart

74
Q

Endocardium

A

thin serous membrane lining the inner chambers of the heart and valves

ECG (3 decks)

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