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Cardiovascular Monica xx > origin + conduction of cardiac impulse > Flashcards

origin + conduction of cardiac impulse Flashcards

1
Q

what is the heart

A

electrically controlled muscular pump which sucks and pumps blood

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2
Q

where are electrical signals which control the heart generated

A

within the heart

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3
Q

the heart is capable of beating rhythmically in the absence of external stimuli (T/F)

A

True

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4
Q

what is autorhythmicity

A

heart is capable of beating rhythmically in the absence of external stimuli

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5
Q

excitation originates

A

pacemaker cells in sino-atrial node

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6
Q

what initiates heart beat

A

cluster of specialised pacemaker cell in SA node

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7
Q

where is the SA node located

A

Upper right atrium

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8
Q

SA node does not drive entire heart (T/F)

A

False - does drive entire heart

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9
Q

What is sinus rhythm?

A

Heart controlled by sino-atrial node

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10
Q

How does cardiac excitation originate?

A
  • cells in SA node = no stable resting membrane potential
  • cells in SA node = generate regular spontaneous pacemaker potentials
  • spontaneous membrane potential takes membrane potential to threshold
  • every time threshold reached = action potential
  • –> regular spontaneous action potentials in SA node
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11
Q

define pacemaker potential

A

slow depolarisation of membrane potential to a threshold

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12
Q

pacemaker potential due to

A
  • decrease in K+ efflux
  • Na+ and K+ influx
  • transient Ca++ influx
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13
Q

explain rising phase of action potential

A
  • depolarisation
  • activation of long lasting L-type Ca++ channels
  • Ca++ influx
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14
Q

explain falling phase of action potential

A
  • repolarisation
  • activation of K+ channels
  • K+ efflux
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15
Q

Cell-to-cell current flow moves via

A

Gap junctions

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16
Q

Give characteristics of the AV node

A
  • small bundle of specialised cells
  • located at base of right atrium just above junction of atria and ventricles
  • only point of electrical contact between A + V
  • smal in diameter
  • slow conduction velocity
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17
Q

Spread of Excitiation

A

-across atria = cell-to-cell conduction via gap junctions
-SA to AV node = cell-to-cell conduction via gap junctions
AV node = conduction delayed (atrial systole to proceed ventricular diastole
-Bundle of His, Purkinjie Fibres = rapid spread of action potentials to ventricles
-ventricular muscle = cell-to-cell conduction

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18
Q

Phase 0 of ventricular muscle action potential

A

fast Na+ influx

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19
Q

Phase 1 of ventricular muscle action potential

A

closure of Na+ channels

transient K+ efflux

20
Q

Phase 2 of ventricular muscle action potential

A

mainly Ca++ influx

AKA plateau phase

21
Q

Phase 3 of ventricular muscle action potential

A

Closure of Ca++ channels and K+ efflux

22
Q

Phase 4 of ventricular muscle action potential

A

Resting membrane potential

23
Q

sympathetic stimulation

A

increases HR

24
Q

parasympathetic stimulation

A

decreases HR

25
Q

Heart rate is mainly controlled by what system?

A

Autonomic nervous system

26
Q

Explain vagus nerve

A
  • parasympathetic supply to heart

- continuous influence on SA under normal resting conditions

27
Q

Explain vagus tone

A
  • dominates under normal resting conditions
  • slows intrinsic heart rate
  • 100 to 70bpm
28
Q

Normal resting heart rate values

A

60-100 bpm

29
Q

Resting heart rate less than 60bpm =

A

bradycardia

30
Q

resting heart rate more than 100bpm =

A

tachycardia

31
Q

what does vagus nerve supply?

A

SA and AV node

32
Q

Vagal stimulation

A

slows HR

increases AV nodal delay

33
Q

what is the neurotransmitter in parasympathetic supply of the heart

A

acetyl choline acting through muscarinic M2 receptors

34
Q

what is atropine

A

-competitive inhibitor of acetylcholine

35
Q

when is atropine used

A

extreme bradycardia (speeds up the heart)

36
Q

outline the effects of vagal stimulation on pacemaker potentias

A
  • cell hyperpoalrises
  • longer to reach threshold
  • slope of pacemaker potential decreases
  • frequency of AP decreases
  • negative chronotropic effect
37
Q

what does cardiac sympathetic nerves supply?

A

SA node
AV node
Myocardium

38
Q

what does sympathetic stimulation do

A
  • increase HR
  • decrease AV nodal delay
  • increases contraction force
39
Q

what is the sympathetic supply of the heart neurotransmitter

A

noradrenaline acting through B1 adrenoreceptos

40
Q

noradrenaline effect on pacemaker cells

A
  • pacemaker potential slope increases
  • pacemaker potential reaches threshold quicker
  • frequency of action potentials increases (positive chrronotropic effect)
41
Q

what is an ECG?

A

record of depolarisation and repolarisation cycle of cardiac muscle obtained from skin surface

42
Q

P wave

A

Atrial depolarisation

43
Q

QRS Complex

A

Ventricular depolarisation

44
Q

T wave

A

Ventricular depolarisation

45
Q

PR interval

A

Largely AV node delay

46
Q

ST segment

A

Ventricular systo;e

47
Q

TP interval

A

Diastole

Cardiovascular Monica xx (6 decks)

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