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HUBS192 Melia > Lecture 9: THE EXCITABLE HEART > Flashcards

Lecture 9: THE EXCITABLE HEART Flashcards

1
Q

What are the types of cells in the heart?

A

Electrical/conduction and contractile

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2
Q

What % of cells in the heart are electrical/conduction?

A

1%

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3
Q

What % of cells in the heart are contractile?

A

99%

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4
Q

What are the types of electrical/conduction cells?

A

Purkinje cells and AV nodal cells

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5
Q

What is the appearance of electrical/conduction cells?

A

Pale striated

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6
Q

What is the actin and myosin content of electrical/conduction cells?

A

Low

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7
Q

What is the aim of electrical/conduction cells?

A

To transmit an electrical signal as quickly as possible from cell to cell

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8
Q

What % of cells in the heart are contractile?

A

99%

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9
Q

What are the names of contractile cells?

A

Myocardial cells

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10
Q

What is the appearance of contractile cells?

A

Striated

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11
Q

What is the actin and myosin content of contractile cells?

A

HIgh

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12
Q

What is the aim of contractile cells?

A

To contract the heart

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13
Q

Where does the action potential in the heart propagate?

A

Along the surface membrane of electrical and contractile cells

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14
Q

Where does depolarisation start?

A

At the sinoatrial node (SAN)

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15
Q

Where’d does the signal spread?

A

To neighbouring cells (contractile and conduction)

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16
Q

What does increased cytosolic calcium levels do in a contractile cell?

A

Cause cross bridge attachment and contraction

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17
Q

What do intercalated discs do?

A

Connect most cells of the heart

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18
Q

What do intercalated discs contain?

A

Gap junctions

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19
Q

What are gap junctions?

A

Pores with low resistance to ionic current (electrical ionic current passes through easily)

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20
Q

What do gap junctions allow?

A

Current to flow between adjacent cells

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21
Q

Where do gap junctions spread the impulse?

A

Along the conduction pathway

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22
Q

Where does the impulse spread between?

A

Electrical and contractile cells and also between contractile cells

23
Q

What do gap junctions increase?

A

The speed of the impulse throughout the heart

24
Q

What do the millions of cardiac cells have to do?

A

Behave as one

25
Q

What is a functional syncytium?

A

Many cells cooperating as one unit

26
Q

What is the SA node?

A

The pacemaker for the heart which tells it when to beat (does not require the brain or nerves)

27
Q

Where is the SA node found?

A

On the top of the right atrium

28
Q

Where does the conduction pathway start?

A

At the SA node

29
Q

Where does the SA node send the signal?

A

3 places - right atrium, left atrium via the intertribal bundle and to the AV node down the intertribal bundle

30
Q

When does contraction of the atria occur?

A

When the signal reaches them and while the rest of the heart is still yet to receive the signal

31
Q

What does the AV node do?

A

Collects the signal from the SA node and pauses it for a moment before sending it along the AV bundle

32
Q

Why does the AV node pause the signal?

A

So that the atria can contract and relax before the ventricles begin to contract

33
Q

What are the AV bundle branches?

A

2 branches of the AV bundle

34
Q

What do the AV bundle branches do?

A

Take the signal to the bottom of the heart down the septum and then to the purkinje fibres

35
Q

What do the purkinje fibres do?

A

Take the signal up the sides of the heart wall

36
Q

Where does the signal start in the ventricles?

A

At the bottom and moves its way upwards as this is the most efficient way to remove a lot of blood out the aorta and pulmonary arteries

37
Q

What is the first step of the excitation and conduction pathway?

A

The signal is spread from the SA node and depolarisation of the atria begins

38
Q

What happens after the signal is spread from the SA node and depolarisation of the atria begins?

A

The atria are fully depolarised and contract. Signal has reached the AV node and is being held there

39
Q

What happens after the atria are fully depolarised and contract. Signal has reached the AV node and is being held there?

A

The atria repolarise and relax, while the AV node sends excitation (depolarisation) down the septum to the ventricles

40
Q

What happens after the atria depolarise and relax, while the AV node sends excitation (depolarisation) down the septum to the ventricles?

A

Atria are fully relaxed while the ventricles are fully depolarised and contract (isovolumetric contraction and ventricular ejection)

41
Q

What does ECG stand for?

A

Electrocardiogram

42
Q

What is the lead in an ECG?

A

A virtual line between two surface electrodes

43
Q

What does a single lead do?

A

Detects a difference between electrodes (depolarisation and repolarisation)

44
Q

What are the features of an ECG line?

A

P wave, QRS complex and T wave

45
Q

What causes the P wave?

A

Atrial depolarisation initiated by the SA node

46
Q

When is the impulse first delayed?

A

When atrial depolarisation is complete and the signal is being held at the AV node

47
Q

What causes the QRS complex?

A

Ventricular depolarisation beginning and atrial repolarisation occurring

48
Q

What happens in the gap between the QRS complex and the T wave?

A

Ventricular contraction is complete

49
Q

What causes the T wave?

A

Ventricular repolarisation begins

50
Q

What happens after the T wave?

A

Ventricular repolarisation is complete

51
Q

What is the first heart sound?

A

Lubb

52
Q

What happens during lubb?

A

The AV valves snap shut

53
Q

What is the second heart sound?

A

Dupp

54
Q

What happens during dupp?

A

The semilunar valves close

HUBS192 Melia (38 decks)

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