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Physiology I Block 4 > Regulation of Heart Pacemaker Potential > Flashcards

Regulation of Heart Pacemaker Potential Flashcards

(63 cards)

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1
Q

how are cardiac cells connected

A

gap junctions

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2
Q

how do impulses move in heart muscle

A

cell to cell not through nerves, via gap junctions

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3
Q

heart cells are ______ coupled

A

electrically

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4
Q

what is the RMP of SA node

A

-55 to -65 mV

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5
Q

the RMP of SA node is very ______

A

unstable

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6
Q

SA node is very leaky to

A

Na+ and Ca++

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7
Q

describe RMP of SA node

A

they are very leaky to Na+ and Ca++ so when it goes down to RMP the Na and Ca bring the RMP more positive so it will depol

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8
Q

what causes depol in SA node

A

voltage gated L type Ca++ channels

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9
Q

if current is activated at what mV

A

-60

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10
Q

when if channel opens what happens

A

sodium leadks into cell, this is for SA node

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11
Q

when SA node is -50 mv what channel opens

A

iCaT (transient)

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12
Q

what is the third channel that opens in SA node under threshold

A

iCaL

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13
Q

desribe what is happening until threshold is reached in SA node

A

if channels open which cause Na to enter, then iCaT open then IcaL open

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14
Q

what is threshold in SA node

A

about -30 mv

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15
Q

what are the phases in SA node

A

4, 0, 3, 4

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16
Q

depol of SA node is due to

A

calcium entering cell

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17
Q

what happens at peak of SA node curve

A

calcium channels close and potassium currents open

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18
Q

does the SA node contract

A

no

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19
Q

SA nodal cells fuse with:

A

atrial muscle cells
anterior interatrial band cells
internodal pathway cells

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20
Q

what is the anterior interatrial band

A

it passes from right atrium to left so they depol and contract together

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21
Q

what is the internodal pathway

A

brings the impulse from SA node to AV node

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22
Q

what is job of AV node

A

slow the impulses from SA

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23
Q

why is it important to slow down the impulses from the SA by the AV

A

so the atria can contract before the ventricle

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24
Q

describe rate of rise in AP of AV and SA node

A

SA much steeper, AV takes longer to get to threshold

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25
b/w atria and ventricle is piece of fibrous tissue:
AV bundle
26
what is purpose of AV bundle
muscular connection b/w atrium and ventricle, prevents re-entry of cardiac impulses into atria from ventricle
27
what is the only muscular connection b/w atria and ventricle
AV bundle
28
why is there delta wave in WPW
accessory ptahway starts to depol the ventricles too soon
29
after AV node where does impulse go
lef tand right bundle branches then purkinje fibers
30
describe conduction through purkinje fibrs
very fast - allows the impulse to spread quickly through ventricles
31
why are impulses so fast through purkinje fibers
bigger, more gap junctions, AP spike faster
32
purkinje fibers spread the AP quickly and then it gets to ventricles and it
slows down a little bit
33
why is there delay b/w QRS wave and ventricles contracting
electrical activity has to be converted to mechanical contractility, that takes time
34
only thing you are measuring with ECG is
electrical activity
35
depol vs. repol
depol causes another to depol, but repol just happens on its own. there is inherent property within cells that tells them how long they should stay depol
36
AP duration in endocardial cells is shorter than
epicardial cells ( i think its actuallyosute doublencheck)
37
what is intrinsic rhythmical rate
70-80 times/min
38
what is purkinje fibers rate
15-40 timesmin
39
why is SA node the pacemaker
it fires faster
40
what is ectopic pacemaker
anther area of heart fires faster than SA node so it becomes the pacemaker
41
sinus arrest - what is person's heart rate
40-60 b/c AV node will kick in
42
what is sinus arrest
SA node stops working
43
3rd degree block what will HR be
15-40 times/min (purknje fibers)
44
PNS originates in
medulla
45
vagus nerve is nerve
trunk
46
vagus nerve has efferent nerves going to heart and it also has
afferent sensory nerves monitoring heart
47
what does it mean that vagus nerve is nerve trunk
it has efferent and afferent nerves to heart to monitor and control
48
vagus primarily moderates (PNS)
SA and AV node
49
sympathetic nerves primarily innervate
SA, AV, and ventricular muscle
50
there is almost no PNS control of
muscle itself
51
Parasympathetic releases what
ACh
52
what is the kindo f receptor for ACh
G protein coupled muscarinic receptor
53
what is affect of parasympathetic onheart
inhibitory
54
what is released from postganglionic nerve sympathetic
NE
55
NE is a
catecholamine
56
catecholamine
dopamine, NE, EPI
57
dopamine is converted into
NE
58
what is receptor for sympathetic, NE
betaadrenergic receptor
59
what nerves increase rate of conraction
sympathetic nerves
60
activation of beta receptors inheart does what to SA node
increases firing rate, makes them more leaky to sodium and calcium
61
how does beta receptors in heart increase SA node
they make them more leaky to sodium and calcium
62
how do muscarinic receptors slow or stop heart rate
they open voltage sensitive potassium channels to cause hyperpolarization
63
if sympathetic is high, PNS is
low

Physiology I Block 4 (13 decks)

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