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Cardiovascular > Unit 1 Day 2 > Flashcards

Unit 1 Day 2 Flashcards

1
Q

Slow Action Potential

A
  • pacemaker cells of SA and AV nodes

- contains ICa-T + ICa-L, If, IKr, and IKs ion channels

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2
Q

Fast Action Potential

A
  • Myocardial cells and cells of the rapid conduction pathways display fast action potentials (atrial and ventricular muscles and purkinje fibers)
  • phase 0
  • phase 1
  • phase 2
  • phase 3
  • phase 4
  • contains INa, ICa-L, IKto, IKr + IKs, IK1 ion channels
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3
Q

pacemakers

A
  • cells in heart that can initiate heart beat

- usually SA node

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4
Q

IK1 Ion Channels

A
  • present in fast cardiac action potentials only
  • inward rectifier cells
  • readily conduct K+ inwards at potentials below Ek
  • hold cells near Ek between action potentials without producing an outward current upon depolarization that would be energetically costly and make it more difficult to generate an action potential
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5
Q

If Ion Channels

A
  • present in slow cardiac action potentials only
  • turned off at depolarized potentials and turned on at hyperpolarized potentials
  • permeable to both Na+ and K+
  • plays important role in pacemaking in SA node
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6
Q

overdrive suppression

A
  • cells in other regions of heart are capable of spontaneous activity, but they normally fire action potentials at slower rate than SA nodal cells
  • thus, these cells are normally driven by action potentials originating in SA node
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7
Q

Absolute Refractory Period

A
  • refers to depolarization and repolarization (main hump on action potential curve)
  • period immediately following the firing of a nerve fiber when it cannot be stimulated no matter how great a stimulus is applied
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8
Q

Relative Refractory Period

A
  • refers to hyperpolarization

- greater than normal stimulus can generate second response

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9
Q

ectopic pacemaker

A

-when cells other than SA node take over initiation of heartbeat

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10
Q

Relationship between the ventricular action potential in a cardiac myocyte and the corresponding surface ECG

A
  • phase 0 = initial upward deflection of “R” wave
  • phase 1 = QRS (R wave)
  • phase 2 = ST interval
  • phase 3 = T
  • phase 4 = isoelectric segment after T wave
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11
Q

Components of ECG

A
  • P wave- atrial depolarization
  • QRS- ventricular depolarization
  • T wave- ventricular repolarization
  • PR interval- index of conduction time across AV node
  • QT interval- total duration of depolarization and repolarization of ventricle
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12
Q

3 Types of Atrioventricular Block

A

-1st degree-conduction delayed but all P waves conduct to the ventricles
-2nd degree-some P waves conduct but others do not
-3rd degree-none of the P waves conduct & a ventricular
pacemaker takes over

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13
Q

Bundle Branch Block

A

-right bundle block- QRS widening with delayed conduction
to the right ventricle
-left bundle block -QRS widening with delayed conduction
to the left ventricle
-left bundle fascicles block- there are shifts in direction of
depolarization but no QRS widening

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14
Q

Bundle of His

A
  • From the AV node the electrical impulse travels down the Bundle of His
  • His divides into the right and left bundle branches
  • The right bundle branch contains one fascicle
  • The left bundle branch subdivides into two fascicles: the left anterior fascicle and the left posterior fascicle
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15
Q

3 Common Mechanisms Leading to Arrhythmia

A
  • abnormal reentry pathways
  • ectopic foci
  • triggered activity
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16
Q

Long QT Syndrome

A
  • caused by EADs and DADs
  • mutation on channel causes reduced current which causes inc. QT interval
  • LQT1-K+ channel
  • LQT2- dec K+ current
  • LQT3- incomplete Ina inactivation
  • LQT5- dec. K+ current
  • LQT6- dec. K+ current
  • LQT7- dec. K+ current
  • LQT8- incomplete Ica inactivation
17
Q

Class 1 Antiarrhythmic Drugs

A
  • all are Na+ channel blockers (block phase 0 of fast?)
  • drug stabilizes inactivated channel state
  • class 1b: lidocaine
  • 1a and 1c also block K+ (phase 3) of slow and fast?
  • class 1b is pure class 1 action: slow upstroke, dec. action potential duration
  • use dependent- channels must be working for drug to enter
  • channels blocked with drug EXHIBIT LONGER REFRACTORY PERIOD
18
Q

Class 2 Antiarrhythmic Drugs

A
  • beta blockers
  • dec. If (Na+ and K+), Ica-L (Ca+), and Ik (K+) current
  • class 2 drugs cause dec. slope of phase 4 diastolic depolarization (slow and fast?)
  • pacing rate is reduced
  • refractory period is prolonged
  • used to terminate AV nodal re-entry and to control ventricular rate during atrial fibrillation
  • dec. phase 4 slope causes dec. rate of firing, causes dec. automaticity
  • dec. re-entry and automaticity
  • blocks beta adrenergic
  • focuses in SA and AV node
19
Q

Class 3 Antiarrhythmic Drugs*

A
  • block K+ channels
  • causes prolongation of phase 2 (fast)and leads to inc. inactivation of Na+ channels
  • prolongs refractory period
  • class 3 drugs: AMNIODARONE- reduces conduction velocity
20
Q

Class 4 Antiarrhythmic Drugs*

A
  • Ca+ channel blockers
  • drug stabilizes Ca2+ channel inactivated state-use-dependent blockers of Ica-L channels
  • principle effects are in nodal cells
  • Ca2+ channel blockers dec. upstroke rate and this causes DEC. conduction velocity
  • prolongs refractory period
  • suppresses re-entrant arrhythmias by prolonging refractory period
21
Q

Unclassified Antiarrhythmic Drug: Adenosine

A
  • works in SA and AV node
  • inc. K+ current
  • dec. Ica-L current
  • dec. If in SA and AV nodes
  • dec. SA and AV node firing rate
  • dec. conduction rate in AV node
  • short half life is advantageous
22
Q

abnormal reentry pathways

A
  • can be present in atria, ventricles, or junctional tissue,
    -must be unidirectional and have slow conduction to cause problems
    most common mechanism
    -caused by blockage or injury such as MI
23
Q

ectopic foci

A
  • when a part of heart other than SA node begins initiating heart beats
24
Q

triggered activity

A
  • afterdepolarizations may be triggered by preceding action potential (long QT interval)
  • early afterdepolarization (EAD)- phase 2 and 3, dependent on reactivation of Ca2+ channels in response to inc. intracellular Ca2+
  • delayed afterdepolarization (DAD)-phase 4, initiated by inc. intracellular Ca2+, which causes inc. Na+/Ca2+ exchange, which causes depolarization
25
Q

Inc. refractory period causes:

A

-dec. in re-entrant arrhythmias

Cardiovascular (29 decks)

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