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AY Cardiovascular > Physiology > Flashcards

Physiology Flashcards

1
Q

Where is the SA node located?

A

The upper right atrium

Near where the SVC enters the right atrium

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2
Q

Do the cells in the SA node have a stable resting membrane potential?

A

No

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3
Q

What is spontaneous pacemaker potential?

A

Where membrane potential is taken to a threshold to generate an action potential in the SA nodal cells

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4
Q

What causes the pacemaker potential?

A

Decrease in K+ efflux

Slow Na+ influx (the funny current)

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5
Q

What causes the rising phase of the action potential?

A

Depolarisation caused by activation of voltage gater Ca2+ channels
(CALCIUM INFLUX)

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6
Q

What causes the falling phase of the action potential?

A

Depolarisation caused by activation of K+ channels

K+ EFFLUX

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7
Q

How does excitation spread through the heart

A 
SA node 
Cell-to-cell conduction 
AV node 
Bundle of His 
Left & right branches 
Purkinje fibres
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8
Q

How does excitation spread from SA node to AV node?

A

Via gap junctions

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9
Q

Why is conduction delayed in the AV node?

A

Allows atrial systole (contraction) to precede ventricular systole

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10
Q

What causes phase 0 of the ventricular muscle action potential?

A

Fast Na+ influx

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11
Q

What causes phase 1 of the ventricular muscle action potential?

A

Closure of Na+ channels and transient K+ efflux

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12
Q

What causes phase 2 (plateau phase) of the ventricular muscle action potential?

A

Mainly Ca2+ influx

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13
Q

What causes phase 3 of the ventricular muscle action potential?

A

Closure of Ca2+ channels and K+ efflux

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14
Q

What is phase 4 of the ventricular muscle action potential?

A

Resting membrane potential

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15
Q

Which nervous system mainly influences heart rate?

A

Autonomic Nervous System

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16
Q

What does sympathetic stimulation do to heart rate?

A

Increases heart rate

17
Q

What does parasympathetic stimulation do too heart rate?

A

Decreases the heart rate

18
Q

What is the parasympathetic supply to the heart?

A

Vagus nerve

19
Q

What is a normal resting heart rate?

A

60 - 100 bpm

20
Q

What does vagal stimulation do to the heart?

A

Slows heart rate and increases AV node delay

21
Q

What neurotransmitter is involved in parasympathetic stimulation of the heart?

A

Acetyl choline acting through M2 receptor

22
Q

How does atropine act on the heart?

A

Competitive inhibitor of Acetyl choline - used in extreme bradycardia to speed up the heart

23
Q

What is the effect of vagal stimulation on pacemaker potentials?

A

Slope of pacemaker potentials DECREASES

24
Q

What is the sympathetic supply to the heart?

A

Cardiac sympathetic nerves supply the SA and AV node and the myocardium

25
Q

What does sympathetic stimulation do to the heart?

A

Increases heart rate
Decreases AV node delay
Increases force of contraction

26
Q

What is the neurotransmitter for sympathetic stimulation of the heart?

A

Noradrenaline acting through B1 adrenoceptors

27
Q

What effect does noradrenaline have on pacemaker cells?

A

Slope of pacemaker potential INCREASES

28
Q

Where does the excitation of the heart originate?

A

Pacemaker cells in the SA node

AY Cardiovascular (28 decks)

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