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Fundamentals of Physiology > L5: The Cardiac Cycle > Flashcards

L5: The Cardiac Cycle Flashcards

1
Q

What is the primary pacemaker of the heart?

A

Sinoatrial node (SA node)

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2
Q

Where is the SA node located?

A

Top corner of the right atrium

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3
Q

Function of the SA node

A

Generates an AP that causes the upper part of the heart to contract

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4
Q

Define intrinsic pacemaker activity

A

Beats with a clock-like function & does not require any external stimulus to generate an AP

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5
Q

What happens after the impulse arrives at the AV node?

A

Spreads down the specialist conducting tissue called Bundle of His

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6
Q

Function of Bundle of His

A

Brings excitation to the top of the septum & through

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7
Q

Name two branches in the Bundle of His

A

1) Right bundle branch
2) Left bundle branch

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8
Q

Name of fibres that branch from the apex

A

Purkinje Fibres

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9
Q

What does purkinje fibres do ?

A

Radiate out through the ventricular wall

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10
Q

When does the heart not have its own intrinsic activity?

A

When excitation arrives at the muscle of the heart (atrium & ventricles)

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11
Q

How is the atrial & ventricular AP characterised?

A

Having a flat stable resting membrane potential in between beats

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12
Q

Which node of the heart has the fastest intrinsic rate?

A

SA node

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13
Q

Define intrinsic rate

A

Rate at which the heart beats when all cardiac, neural & hormonal inputs are removed

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14
Q

Role of SA node for being the fastest

A

Determines the rate of all other structures within the heart

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15
Q

2nd fastest intrinsic rate

A

AV node

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16
Q

3rd fastest intrinsic rate

A

Bundle of His

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17
Q

Slowest intrinsic rate

A

Purkinje Fibre

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18
Q

Define cardiac arrhythmias

A

When structures starts firing off at faster rates or at abnormal intervals

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19
Q

Why is conduction from SA to the AV nodes relatively slow?

A

No specialised conducting pathways linking them

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20
Q

What happens when the wave of excitation arrives at the AV node?

A

‘AV PAUSE’

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21
Q

2 Importances of the AV pause

A

1) Prevents high heart rates being transmitted into the ventricles
2) Allow ventricles to fill before wave of excitation is passed from atria down to ventricle

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22
Q

What happens in conditions like atrial fibrillation (AF)?

A

Atria beating too fast, resulting in ventricles not pumping properly

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23
Q

Why do people live happily if they have lethal arrhythmia?

A

AV node filters out high frequencies because of AV pause, prevents high rates being transmitted from right atrium through to ventricles

24
Q

What does ECG stand for?

A

The Electrocardiogram

25
Q

Name the triangle that connects the shoulders to the groin?

A

Einthpoven’s Triangle

26
Q

What does the ECG measure?

A

Electrical activity of the heart

27
Q
A
28
Q

What is the first thing that is recorded in the ECG?

A

Wave of excitation arising in the SA node, the atrial depolarisation

29
Q

What happens after atrial depolarisation?

A

Wave of excitation moves down Hiss Bundle into the right/left bundle branches

30
Q

What happens during depolarisation of the septum (towards the atria)?

A

Wave of depolarisation moves down the Hiss Bundle into the right & left bundle

31
Q

Stage after depolarisation of the septum?

A

Depolarisation of the ventricles (towards apex)

31
Q

What happens during the depolarisation of the ventricles (towards apex) R STAGE ?

A

Wave of excitation moves down towards the apex of the heart & depolarises ventricular muscle

32
Q

What happens to the reading during R: depolarisation of the ventricles?

A

QR gives a big upward ascend

32
Q

Define isoelectric line

A

Baseline of an ECG tracing & denotes resting membrane potential

33
Q

What happens after the depolarisation of ventricles (towards apex)?

A

Depolarisation of ventricles (towards atria)

34
Q

What happens during the depolarisation of ventricles (towards atria) S PHASE ?

A

Wave of excitation turns around the tip of the apex & spreads back up the walls of right + left ventricle

35
Q

After the wave shoots to R, what does the S stage denote?

A

Wave coming down to the isoelectric line

36
Q

What happens after the depolarisation of the ventricles (towards atria) S STAGE ?

A

Repolarisation of the ventricles (towards endocardium)

37
Q

What happens during the repolarisation of the ventricles (towards endocardium) T STAGE ?

A

Wave of repolarisation brings a wave of negativeness through ventricle to give the repolarisation of the ventricle

38
Q

What is the duration of ventricular AP determined from?

A

Time of ventricular depolarisation to the end of the AP (T-wave)

39
Q

Why do we not see a wave of atrial repolarisation?

A

Atria repolarises when ventricular cells depolarises, so it is hidden & lost

40
Q

What does the PQ interval tell us?

A

How fast the wave of excitation spreads from the SA node to the AV node

41
Q

What is the PQ interval a measure of ?

A

Atrial conduction & AV nodal delay

42
Q

What is AV nodal delay?

A

Delays signal to ensure atria is empty of blood before contraction

43
Q

What is the AV block ?

A

If impulse is not passing through AV node properly

44
Q

What does QRS duration tell us ?

A

How fast wave of depolarisation spreads from top of ventricle down through ventricles

45
Q

What does it mean when the QRS duration is long?

A

Wave of excitation takes long to spread through ventricle

46
Q

Define ventricular conduction velocity

A

Speed at which electrical signal travels through heart muscle

47
Q

What does the QT interval useful for?

A

Index of AP duration

48
Q

Define diastole

A

Gap in between beats

49
Q

Define systole

A

Contractile phase

50
Q

Define isovolumic contraction

A

Contraction of a closed ventricle without a change in volume, pressure rises in ventricle

51
Q

Define ventricular ejection

A

When volume of blood is ejected out of LV

52
Q

Define dichotic notch

A

When aortic valve snap shuts when LV pressure is lower than aortic pressure

53
Q

When does mitral valves open?

A

When LV pressure is lower than LA pressure

54
Q
A

Fundamentals of Physiology (11 decks)

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