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Cardio > 4. Conduction System > Flashcards

4. Conduction System Flashcards

1
Q

What is the difference between depolarisation and hyperpolarisation?

A

Depolarisation making the membrane potential more positive
Hyperpolarisation making the membrane potential more negative

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2
Q

Define channel, pump and carrier proteins

A

Channel - protein pore that allows facilitated diffusion of ions
Pump - moves ions against concentration gradient by a conformational change in the membrane spanning protein using ATP
Carrier - proteins that transfer ions or molecules by a conformational change in the membrane spanning protein

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3
Q

Why is there a difference in electrical potential inside vs outside of the cell?

A

Differences in concentrations of ions inside and outside of the cell
Selectively permeable

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4
Q

What are the two main membrane pumps in the CV system?

A

Na-K-ATPase
Ca-ATPase

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5
Q

What happens to the electrochemical potential inside of a cell when potassium ions leave?
[also known as the cells resting potential]

A

Becomes more negative

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6
Q

True/false
The cardiac action potential underlies myocardial function

A

True

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7
Q

LOOK ON OSMOSIS FOR CARIDAC ACTION POTENTIAL

A
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8
Q

How are cardiomyocytes electrically linked?

A

Via gap junctions

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9
Q

What is a syncytium? With regard to the heart

A

A network of electrically connected cardiac muscle cells

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10
Q

What is connexin 45 Cx45?

A

A gap junction [pore] linking two cells

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11
Q

What stops cells from firing spontaneous action potentials?

A

The cells ‘recover’ from the action potentials with refractory periods

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12
Q

Where does the spread of excitation start?

A

Sinoatrial node

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13
Q

Describe the pathway of the wave of excitation from the SA node

A

Sa node
Atria
Av node
Purkinje fibres
Ventricular tissue

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14
Q

Describe the process by which spontaneous action potentials that control heart rate are fired.

A

Unstable baseline that gradually depolarises [slow leak of Na+]
Threshold reached for opening voltage gated T type calcium channels
The further depolarisation causes opening of L type calcium channels
Voltage gated potassium channnels open to restore the membrane potential to a negative level
Process starts again

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15
Q

What is the funny current?

A

The slow Na+ leak into the cell

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16
Q

What does an ECG measure?

A

The movement of charge through the myocardium

17
Q

What is the theoretical membrane potential?

A

What the membrane potential would be for a membrane that is perfectly selective for a specific ion with known intracellular and extracellular concentrations

18
Q

What is the equation used for theoretical membrane potential?

A

Nernst equation

19
Q

Why is the resting membrane potential never at Ek ?

A

There is always movement of other ions

20
Q

The opening of potassium channels leads to _______ of the membrane which causes relaxation of muscle

A

Hyperpolarisation

21
Q

Opening channels that pass either calcium or sodium ions causes ________ of the membrane which causes contraction of muscles

A

Depolarisation

22
Q

Describe the electrical activity before a heart beat in non pacemaker cells.

A

Phase 0 - Sodium channels open causing depolarisation
Phase 1- Rapid transient outward current [ITo] of potassium - initial Repolarisation
Phase 2 - ca and k both moving at same time so plateau phase. Long lasting Ca current [sustained depolarisation] from L type calcium channels [Ica]
Phase 3- calcium channels start to close, rapidly activating K+ current [IKr] & slowly activating K+ current [IKs] cause polarisation
Phase 4- inwardly rectifying K+ current IK1

23
Q

What phase of the cardiac action potential is depolarisation?

A

0

24
Q

How long is the phase 2 of the cardiac action potential [long lasting depolarisation]

A

200-300 milliseconds long

25
Q

What does the SAN tissues do to control heart rate`/

A

Fires spontaneous action potentials

26
Q

What is the stimulus that triggers the ventricular action potential?

A

Unstable baseline that slowly depolarises [slow leak of na]
Reaches threshold for opening voltage gates T type calcium channels
This further depolarises the membrane causing opening of L type calcium channels
Voltage gated potassium channels then open to restore the membrane potential to a negative level
- process starts again

27
Q

What is the p wave in an ECG?

A

Atrial depolarisation

28
Q

What is the QRS complex in an ECG?

A

Ventricular depolarisation

29
Q

What is the t wave in an ECG?

A

Ventricular Repolarisation

30
Q

Where is atrial Repolarisation in an ecg and why is it hidden?

A

QRS complex
Hidden by ventricular depolarisation

31
Q

What does upwards section adn downwards sections of an ECG mean about movement of charge?

A

Upwards - movement towards virtual electrode
Downwards - movement away from virtual electrode

32
Q

Where does lead ll “look” in an ecg?

A

Along axis of heart from apex to base

Cardio (9 decks)

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