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Cardiovascular 2018 > Origin and Conduction of Cardiac Impulse > Flashcards

Origin and Conduction of Cardiac Impulse Flashcards

1
Q

What initiates the heart beat in a normal individual?

A

The SA node

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2
Q

Where is the SA node located?

A

The right upper atrium close to the entry point of the SVC

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3
Q

What is it called when a heart is driven by the SA node?

A

Sinus rhythm

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4
Q

What is the pacemaker potential?

A

The slow depolarisation of the membrane

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5
Q

What causes the pacemaker potential?

A

Decrease in K efflux
Na and K influx (funny current)
Transient Ca influx (T type Ca channels)

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6
Q

What is the rising phase of action potential caused by?

A

Activation of long lasting L-type channels

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7
Q

What causes the falling phase of the membrane potential?

A

Inactivation of Ca channels and activation of K channels

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8
Q

Where is the AV node located?

A

The base of the right atrium between the junction of the atria and the ventricles

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9
Q

What is the importance of AV nodal delay?

A

Allows systole to precede diastole.

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10
Q

Describe the phases of the action potential on atrial and ventricular myocytes?

A 
Phase 0
Fast Na+ influx
Phase 1
Closure of NA channels and transient K influx
Phase 2 
mainly Ca influx
Phase 3
Closure of Ca channels and k efflux
Phase 4 
resting membrane potential
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11
Q

What is a normal resting heart rate?

A

60-100bpm

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12
Q

What is the medical terms for slow and fast HR

A

Bradycardia and Tachycardia

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13
Q

What changes the Heart rate?

A

The ANS

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14
Q

What does the sympathetic and parasympathetic system do to the HR?

A

Sympathetic- increases

Parasympathetic-decreases

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15
Q

What dominates the heart in resting conditions?

A

Vagal tone

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16
Q

What does vagal stimulation do?

A

Slow the HR by slowing the rate of firing of the SA node and increases AV nodal delay

17
Q

What is the parasympathetic neurotransmitter and which receptors do they act through?

A

ACH through M2 receptors

18
Q

What is atropine?

A

Competitive inhibitor of ACH: used in extreme bradycardia to speed up the heart

19
Q

Where is the sympathetic supply of the heart?

A

supplies SA node and AV node and myocardium

20
Q

What is the sympathetic neurotransmitter and the receptor it works through?

A

noradrenaline acting through B1 adrenoreceptors

21
Q

What is the effect of sympathetic stimulation on the pacemaker potential?

A

Slope increases and frequency of action potentials increase

22
Q

What does the P wave represent?

A

Atrial depolarisation

23
Q

What does the QRS wave represent?

A

Ventricular depolarisation

24
Q

What does the T wave represent?

A

Ventricular repolarisation

25
Q

What does the PR interval represent?

A

largely AV nodal delay

26
Q

What does the ST segment represent?

A

ventricular systole

27
Q

What does the TP interval represent?

A

diastole

Cardiovascular 2018 (39 decks)

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