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CVR Biweekly 1 > Cardiac Conduction and Mechanics > Flashcards

Cardiac Conduction and Mechanics Flashcards

1
Q

how fast a signal moves through the heart

A

velocity of conduction

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2
Q

velocity of conduction dependent on 3 things:

A
  1. muscle cell diameter
  2. # of gap junctions
  3. increase slope of phase 0 of nodal myocyte action potentials
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3
Q

beats per minute

A

heart rate

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4
Q

conduction system of the heart composed of ______

A

specialized cardiac myocytes

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5
Q

conduction signal gets conveyed to ventricles through ______

A

AV node

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5
Q

conduction speed through bundle branches and purkinge fibers

A

fast

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6
Q

conduction speed through AV node

A

slow

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7
Q

what happens if SA node can’t set the heart rate

A

other pacemaker regions will step up, it will just be much slower

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8
Q

only conductive bridge between the atria and ventricles

A

AV node

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9
Q

injury to AV node that causes slow conduction; ventricular rate and atrial rate still same

A

1st degree heart block

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10
Q

injury to AV node that causes intermittent failure of conduction to ventricles; ventricular rate<atrial

A

2nd degree heart block

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11
Q

complete loss of AV node conduction; atria and ventricles beat independently of each other

A

3rd degree heart block

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12
Q

when a 3rd degree heart block happens, where do ventricles get conduction from

A

AV bundle (next in line to AV node)

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13
Q

what happens when AV bundle is injured

A

ventricles get conduction from bundle branches/purkinge fibers that is scary slow (bradycardia)

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14
Q

the more you fill the heart, the more _____ it will contract

A

forcefully (Starling Mechanism)

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15
Q

load the heart is working against

A

arterial pressure (aortic pressure)

16
Q

how much blood did the ventricles fill up with before heart contracts

A

preload

17
Q

depends on arterial pressure decreasing

A

afterload

18
Q

what happens when heart overstretches (this normally doesn’t happen)

A

lose capacity to generate force

19
Q

autonomic regulation of heart that controls blood pressure

A

baroreceptors

20
Q

role of afferents from the heart

A

go from carotid sinus and aorta to brainstem and give message of whether bp is too high or low

21
Q

role of parasympathetic efferents

A

go to SA and AV node and decrease HR and conduction speed

22
Q

role of sympathetic efferents

A

go to SA and AV node, and myocardium and increase HR and speed of conduction and contractility

23
Q

main steps of how parasympathetics decrease HR

A
  1. Ach binds to Gi couple receptor on SA node
  2. reduces cAMP
  3. decreases HCN (less Na+ leaking)
  4. K+ opens
24
Q

overall effect of parasympathetics on heart

A

decrease pacemaker rate of SA/AV nodes

25
Q

main steps of how sympathetics increase HR

A
  1. NE binds B1 (Gs coupled receptor)
  2. increases cAMP
  3. increases HCN (more Na+ leak)
26
Q

overall effect of sympathetics on heart

A

increased pacemaker rate of SA and AV node and increased contractility (whole curve shifts up)

27
Q

relative force that can be generated at any given muscle length

A

contractility

28
Q

how sympathetics cause an increase in contractility

A
  1. NE binds B1 receptors on ventricular myocytes
  2. increase cAMP and PKA
  3. increase Ca2+ (L-type)
29
Q

increasing contractility of heart increases what

A

stroke volume (how much blood is pumped per 1 beat)

30
Q

sympathetic stimulation increases speed of what two things

A

contraction and relaxation

31
Q

what reduces the duration of action potential plateau by inhibiting PLB and increasing sequestration of Ca2+

A

NE binding to B1 and increasing cAMP and PKA (phosphorylation of PLB)

32
Q

a reduced duration of action potential plateau shortens systole and allows for what

A

better diastolic filling at higher HR’s

33
Q

chronotropy

A

rate

34
Q

inotropy

A

contractility

35
Q

lusitropy

A

relaxation rate

36
Q

dromotropy

A

conduction velocity

CVR Biweekly 1 (19 decks)

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