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Pathophysiology III > Block I: CV II > Flashcards

Block I: CV II Flashcards

1
Q

the heart beat starts in [] and spreads to []

A
  1. specialized cardiac conduction cells (pacemaker)

2. all parts myocardium

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2
Q

what node is most vulnerable to injury, disease and inflammation and why is this?

A

the SA node

because it is located 1 mm beneath visceral pericardium

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3
Q

the SA node is heavily innervated by []

A

sympathetic and parasympathetic fibers

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4
Q

after the SA nodes, where to APs go?

A

AV nodes

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5
Q

what are the 3 atrial fibers that connect the SA node to the AV node

A
  1. anterior
  2. middle (tract of wenckebach)
  3. posterior (tract of thorel)
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6
Q

after the AV node where do APs go?

A

bundle of his

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7
Q

[] is a triangle shaped node that lies within the posterior border of interventricular septum

A

bundle of his

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8
Q

the two lower ends of the triangle of the bundle of his give rise to []

A

R and L bundle branches

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9
Q

describe depolarization

A

cells become transiently positive due to influx of Na and Ca ions

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10
Q

what leads to repolarization

A

return to more neative charge, pumping out of K +

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11
Q

describe the AP route of travel

A
  1. SA node
  2. 3 internodal pathways (anterior, middle, posterio)
  3. AV node
  4. bundle of his
  5. purkinje fibers
  6. ventricular myocardium
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12
Q

activation is AKA []

A

depolarization

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13
Q

deactivation is AKA []

A

repolarization

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14
Q

describe the refractory period

A

heart muscles cannot contract, ensures diastole and completes cardiac cycle

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15
Q

why is the AP delayed in the region of the AV node?

A

to permit ventricular filling by atrial contraction (atrial kick)

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16
Q

what ions are involved in muscle cell APs

A
  1. Cl-
  2. Na+
  3. Ca+
  4. K+
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17
Q

[] is the movement of ions in and out of a cell that creates voltage across the cell membrane

A

membrane potential

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18
Q

[] is an electrical charge difference

A

voltage

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19
Q

[] is the difference between resting membrane potential and decreased negative charge causes by depolarization

A

cardiac action potential

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20
Q

what is the resting membrane potential of myocardial fibers

A

-90 mV

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21
Q

[] is recorded extracellularly in summed electrical activity of all cardiac muscle fibers, and is a combined electrical record whose overall shape reflects electrical activity from cells of different regions of the heart

A

ECG

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22
Q

as Ih (hyperpolarization) increases membranes []

A

depolarize, noticed that cell is becoming to negative to positive ions will be drawn in

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23
Q

what are the two types of calcium channels

A
  1. T (transient)

2. L (long)

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24
Q

AP in pacemaker cells of the SA and AV nodes are primarily caused by what ion?

A

Ca++ (relatively no contribution from Na+ influx)

which is why CCBs are used to help with HTN

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25
Q

is there a sharp, rapid depolarizing spike before the plateau in pacemaker potentials

A

no

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26
Q

ACH [increases/decreases] nerve firing rates

A

decreases

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27
Q

cholinergic fibers release [] to [] HR and are a part of the [] nerve

A
  1. ACH
  2. DECREASE
  3. VAGUS
28
Q

when cholinergic vagal fibers are stimulated, membrane becomes []

A

hyperpolarized, slope of prepotential is decreased

29
Q

how does ACH slow down APs?

A

nodal tissues membrane permeability is increased for K+, which leaks out of cell and causes repolarization

-this occurs via M2 muscarinic receptors

also decreases cAMP, which slows Ca2+ channel openings and decreases firing rate

SLOWS depolarizing effect of Ih

30
Q

sympathetic noradrenergic stimulation [increases/decreases] membrane potential of SA node

A

increases

31
Q

what is the effect of sympathetic noradrenergic stimulation of SA node

A

increases membrane potential of SA node
-stimulation of sympathetic cardiac nerves SPEEDS up depolarizing effect of Ih

so that rate of spontanenous discharge increases

32
Q

NE secreted by sympathetic nerve endings bind [] receptors to increase cAMP which []

A
  1. beta-1

2. increases L Ca2+ channels to increase Intracellular Ca and the rapidity of depolarization phase of the impulse

33
Q

as temperature increases, discharge frequency []

A

increases

explains why tachycardia is assoc. with fever

34
Q

[] is the sum of all cardiac action potentials

A

ECG

35
Q

what does the P wave represent

A

Atrial depolarization and conduction through AV node

36
Q

that does the PR interval represent

A

measure of time from the onset of atrial activation to the onset of ventricular activation

i.e. the time necessary to travel from the sinus node to the AV node to the his-purkinje system to ventricular myocardial cells

37
Q

what does the QRS complex represent

A

sum of all ventricular muscle cells depolarization and repolarization

38
Q

what does the T wave represent

A

ventricular repolarization

39
Q

what does the QT interval represent

A

electrical systole of ventricle

-varies inversely with HR

40
Q

what is the purpose of intercalated discs

A

specialized cell junction for the spread of AP

41
Q

which muscles: heart or skeletal- produce more aTP

A

heart

42
Q

which muscles: heart or skeletal have readier access to ions in the interstial space and why

A

heart due to transverse tubules

so it can work constantly ( skeletal muscle doesnt have to)

43
Q

contraction happens with the [] shortens and adjacent [] lines move closer together

A
  1. sarcomere

2. Z lines

44
Q

the width of the A band [remains unchanged, becomes narrower} during contraction

A

remains unchanged

45
Q

the width of the I band [remains unchanged/becomes narrower] during contraction

A

becomes more narrow

46
Q

overlap between thin and thick filaments [increases/decreases] during contraction

A

increases

47
Q

describe the first stage of the cross bridge cycle

A

cross bridge formation

  1. ATP binds myosin head, ATP hydrolyzed to ADP to activate myosin heat
    - hydrolyzed by inorganic phosphate
  2. Ca2+ released from sarcoplasmic reticulum
    - binds to troponin
    - creates conformational change within tropomyosin
    - myosin binding sites on actin made available to mind with myosin head (exposed)
48
Q

what must happen to my myosin head before it can bind with myosin binding sites on the actin filament?

A

it must bind with ATP, that ATP must be hydrolyzed by an inorganic phosphate to ADP to activate the myosin head
-inorganic phosphate will be released

49
Q

what must happen to the tropomyosin before it can bind myosin?

A

Ca2+ will be released from sarcoplasmic reticulum so that it can bind with troponin

binding troponin creates conformational change with tropomyosin

myosin binding sites are made available

50
Q

what is the 2nd stage of the cross bridge cycle

A

power stroke

ADP released from myosin, myosin head pivots to slide thin myofilament closer to center of sarcomere

51
Q

what is the 3rd stage of the cross bridge cycle

A

cross bridge detachment

ATP molecule binds myosin head
-bond between atcin and myosin weakens

52
Q

what is the 4th phase of the cross bridge cycle

A

reactivation of myosin head

ATP hydrolzed to ADP by inorganic phosphate

myosin head reactivated and primed for binding with actin

53
Q

what threshold causes funny Na+ channels to open on Pacemaker Cells

A

< 40 mV

causes a less, negative charge (depolarization)

54
Q

what are two other names for depolarization in pacemaker cells

A
  1. pacemaker potential

2. pre-potential

55
Q

once pacemaker potential is reached, Na+ channels close and [] channels open

what is the threshold?

A

Ca2+

  1. T-type: -50mV
  2. L-type: -40mV

causes further depolarization of cell, rising phase of curve

56
Q

what happens at peak depolarization of pacemaker cells?

A

K+ channels open to allow K+ movement out of cells

Ca2+ channels close

voltage returns to -60mV

57
Q

what is the resting potential of myocytes

A

-90mV (diff from pacemaker, -60mv)

58
Q

what triggers myocyte depolarization

A

when they are stimulated by adjacent cells via IC disc (pacemaker autorhythmic and don’t need stimulation from other cells)

59
Q

ions from adjacent cells cause membrane potential to reach [] in myocardial cells

A

-70mV

causes cell to reach threshold AP

60
Q

what is the threshold AP for myocytes

A

-70mV (-40 for pacemaker)

61
Q

once myocytes are at potential, what happens?

A

fast Na+ channels leak open for rapid influx Na+ which causes depolarization

62
Q

once myocyte reaches [] Ca channels open

A

-40 mV (L-type) causes slow, steady influx of calcium into cell

63
Q

when myocytes reah their peak, what happens?

A

Na+ channels close, while Ca2+ channels remain open.

causes PLATEAU PHASE

64
Q

describe what is happening in the plateau phase are myocardial cells

A

Na+ channels close, while Ca2+ channels remain open. becomes slightly more negative but does hangs around depolarization for a while.

plateau phase distinct for myocardial cells (NOT pacemakers)

65
Q

describe calcium induced calcium release

A

calcium from ion channels stimulate sarcoplasmic reticulum to release more calcium, to bind troponin and allow cross bridge cycle for contraction

66
Q

when does muscle contraction occur in the myocyte?

A

halway through plateau phase, lasts until calcium channels close

67
Q

what happens in myocytes when calcium channels close?

A

K efflux out of cell for repolarization

Pathophysiology III (5 decks)

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