Origin and conduction of cardiac impulse Flashcards

(28 cards)

1
Q

where does excitation of the heart normally originate

A

SA NODE

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2
Q

where is the sa node located

A

right atrium close to where the sperior vena cava enters

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3
Q

what takes the membrane potential to a threshold

A

the spontaneous pacemaker potential and everytime its reached an AP. is generated

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4
Q

what is the pacemaker potential due to

A

the funny current
decrease in k+ efflux
ca+ influx

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5
Q

funny current

A

a depolarising cation current mainly due to slow Na+ INFLUX through HCN channels (hyperpolarisation-activated cyclic nucleotide-gated)

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6
Q

what happens once the threshold is reached

A

the rising phase of action potential is caused by opening of long lasting voltage gate ca+ channels

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7
Q

what occurs during the rising ohase

A

ca+ influx
decreased k+ efflux
funny current

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8
Q

falling phase

A

repolarisation
activation of k+ channels resulting in k+ efflux

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9
Q

what is the falling phase caused by

A

inactivation of l type ca+ channels and activation of k+ channels

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10
Q

where is the av node located

A

base of right attrium

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11
Q

what is the only poiint of electrical contact between atria and ventricles

A

av node

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12
Q

do the cells of the av node have a slow conducting veolicty

A

yes

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13
Q

spread of excitation

A

sa node to av node where it is delayed
bundle of his and its bracnhes and network of purkinje fibres allow rapid spread to ventricles

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14
Q

phase 0 in contractile myocytes

A

fast na+ influx

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15
Q

phase 1

A

closure of na+ channels
k+ efflux

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16
Q

phase 2

A

mainly ca+ influx

17
Q

phase 3

A

closure of ca+
k+ efflux

18
Q

phase 4

A

resting membrane potential

19
Q

plateau phasw

A

membrane potential maintained

20
Q

what is the plateau phase mainly duw o

A

influx of ca+

21
Q

falling phase

A

inactivation of ca+ and activation of k+- k+ efflux

22
Q

what signals atrial depolarisaton

23
Q

what signals ventricular depolarisation

24
Q

pr interval

A

largely av nodal delay

25
when does ventricular systole occur
st segment
26
when does diastole occur
tp interval
27
neurotransmitter in parasympathetic supply
ach acting through m2 muscarinic receptors
28