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HUBS192 2022 > lecture 9 - the excitable heart > Flashcards

lecture 9 - the excitable heart Flashcards

1
Q

What are the 2 types of cells that make up the heart?

A

Electrical and contractile

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2
Q

What is the alternative name for cardiac electrical cells?

A

Conduction cells

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3
Q

What percentage of heart tissue is made up of electrical cells?

A

1%

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4
Q

What is the appearance of cardiac electrical/conduction cells?

A

Pale striations - due to low actin and myosin as contraction is redundant

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5
Q

Purkinje cells and AV nodal cells are examples of what type of cardiac cell?

A

Electrical/conduction cells

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6
Q

What is the appearance of cardiac contractile cells?

A

Striated, due to actin and myosin filaments forming sarcomeres.

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7
Q

Cardiomyocytes are what type of cardiac cell?

A

Contractile cells

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8
Q

How do action potentials propagate along and between cardiac cells?

A

They propagate along the surface membrane of both electrical and contractile cells.

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9
Q

Where do depolarisations that initiate contraction originate in the heart?

A

The sinoatrial (SA) node

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10
Q

How do electrical signals spread between neighbouring cells in cardiac tissue?

A

Via gap junctions

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11
Q

How do gap junctions facilitate the transmission of an electrical signal between cardiac cells?

A

They are pores with low resistance to ionic current, allowing it to flow to the surrounding cells.

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12
Q

How are conduction cells connected in terms of signal transmission?

A

By gap junctions

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13
Q

How are contractile cells connected in terms of signal transmission?

A

Gap junctions

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14
Q

How are conduction cells and contractile cells connected in terms of signal transmission?

A

Gap junctions

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15
Q

Why is the heart described as a ‘functional syncytium?

A

Because all of the cardiac cells behave and contract as one

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16
Q

What are are the key components (in order) of the heart’s conduction pathway?

A

SA node, internodal bundles, AV node, AV bundle branches (left and right), purkinje fibres

17
Q

What connects the SA node and the AV node?

A

Internodal bundles

18
Q

Where is the SA node located?

A

At the superior of the right atrium

19
Q

Where is the AV node located?

A

At the inferior of the right atrium

20
Q

Where do the AV bundle branches run?

A

From the AV node, down the surface of the interventricular septum to the apex of the heart, then branch into perkinje fibres.

21
Q

What are the 2 AV bundle branches?

A

Left and Right

22
Q

Where do purkinje fibres originate?

A

At the end of the AV bundle branches at the apex of the heart

23
Q

Where do purkinje fibres run?

A

Up the left and right ventricles from the apex of the heart.

24
Q

What is the function of the AV node?

A

Helps to transmit electrical signals from the atria to the ventricles. Provides a short delay in transmission to allow the atria to finish contracting before the ventricles start contracting.

25
Q

What are the steps of relaxation, depolarisation and repolarisation during heart contraction?

A

Initially at quiescence (all 4 chambers relaxed), excitation spreads from SA node, atria depolarise, atria repolarise and AV node sends excitation to ventricles, ventricles depolarise and contract, ventricles repolarise, heart fully relaxes again

26
Q

What is the term used to describe the point when the entire heart is relaxed/fully repolarised?

A

Quiescence

27
Q

What are the key features of an ECG trace?

A

P wave, QRS complex, T wave

28
Q

What causes the P wave of an ECG?

A

Atrial depolarisation

29
Q

What causes the QRS complex of an ECG trace?

A

Atrial repolarisation & Ventricular depolarisation

30
Q

What causes the T wave of an ECG trace?

A

Ventricular repolarisation

31
Q

What is the cause of the gap between the P wave and QRS complex?

A

The delay between atrial and ventricular depolarisation, caused by the AV node

32
Q

Why is the QRS complex the largest wave on an ECG trace?

A

The ventricles contain the greatest amount of muscle so create a greater depolarisation

33
Q

What are the 2 heart sounds?

A

Lubb and Dupp

34
Q

What part of an ECG trace is the lubb heart sound associated with?

A

The S wave - end of the QRS complex - ventricular depolarisation complete and isovolumetric phase begins so the atrioventricular valves close

35
Q

What part of an ECG trace is the dupp heart sound associated with?

A

At the end of the T wave - ventricular repolarisation complete and the semilunar valves close

HUBS192 2022 (38 decks)

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