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Systems 2: Cardiovascular > Electrical Properties of the Heart > Flashcards

Electrical Properties of the Heart Flashcards

1
Q

What is excitation contraction coupling?

A

Electrical signals causing physical contraction

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2
Q

What are the main differences between skeletal and cardiac muscle?

A
  • Skeletal muscle is a syncytium (one large fused cell) - Cardiac muscle acts as a syncytium (known as a functional syncytium
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3
Q

What is the function of gap signals in the myocardium?

A

Allow a signal to be propagated from cell to cell

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4
Q

What is the definition of an intercalated disc?

A

Desmosome followed by gap junction followed by desmosome and so on

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5
Q

Why is the AP of cardiac muscle 10 times longer that skeletal?

A
  • Requires calcium from outside the cell as the calcium released from the sarcoplasmic reticulum isn’t enough to saturate enough troponin
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6
Q

What is calcium dependent calcium release?

A

Calcium from outside the cell causes the sarcoplasmic reticulum to release more calcium

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7
Q

What is the strength of heart contraction directly proportional to?

A

How much calcium enters the cell

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8
Q

Why can cardiac muscle not display tetanus?

A

Has a long refractory period and has to relax before it can contract again

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9
Q

What is the resting potential for pacemaker cells?

A
  • Cells sit at an unstable RP - Roughly -60mV
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10
Q

What is the RP of non pacemaker cells?

A
  • About -90mV
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11
Q

What is the permeability of the non pacemaker cells membrane to potassium at RP?

A

High K moves out

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12
Q

What ion causes the rapid depolarisation of non pacemaker cells

A
  • Increase in Na+ permeabilty
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13
Q

What ions permeability changes result in the plateau of repolarisation that allows the refractory period?

A
  • Permeability to Ca2+ which moves in - Permeability to K reduced so more K stays in the cell
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14
Q

What type of calcium channels are responsible for the plateau?

A

L type

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15
Q

How much calcium do L type channels let in?

A

A lot

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16
Q

What allows the actual repolarisation of non pacemaker cells?

A
  • Decrease in Ca2+ permeability - Increase in K+ permeability
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17
Q

STUDY THE DIAGRAM

A
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18
Q

Why is the depolarisation of pacemaker cells slower than non pacemaker cells?

A

Only affected by L type calcium channels and not sodium

19
Q

What is the pacemaker potential?

A

Pre AP potential

20
Q

What causes the pacemaker potential?

A
  • Gradual decrease in PK+
  • Early increase in PNa+ (=PF on diagram)
  • Late increase in PCa2+ (t type calcium channels, small amount of Ca2+)
21
Q

What are the endogenous modulators of electrical activity?

A
  • Autonomic nervous system
  • Temperature (an increase in 1 degree increases the HR by 10bpm)
22
Q

What drugs modulate electrical activity?

A
  • Ca2+ channel blockers that target L type channels
  • Cardiac glycosides
23
Q

How do cardiac glycosides work and what is the most infamous cardiac glycoside?

A
  • Increase force of contraction
  • Digoxin
24
Q

What will be caused by hyperkalemia & hypokalemia?

A
  • Fibrillation and heart block (kalemia refers to serum potassium)
25
Q

What will hypercalcemia cause?

A
  • Increase HR and force of contraction
26
Q

What will hypocalcemia cause?

A

Decreased HR and force of contraction

27
Q

Where are the fastest pacemakers in the heart?

A

Sinoatrial node

28
Q

What is the annulus fibrosis?

A

Non conducting insulator between atrium and ventricle

29
Q

What is the function of the AV node?

A

Delay the AP potential from the SA node to let the left atrium inject it’s blood into the left ventricle

30
Q

What is the first structure that the AP potential travels through in the ventricular wall?

A

Bundle of HIS

31
Q

What is the name of the fibres after the bundle of HIS that the AP travels through to reach bilaterally to both ventricles?

A

Purkinje fibres

32
Q

STUDY THE DIAGRAM

A
33
Q

What is shown by the P wave?

A

Atrial depolarisation

34
Q

What is shown by the QRS complex?

A

Ventricular depolarisation

35
Q

What is shown by the T wave?

A

Ventricular repolarisation

36
Q

What are the 2 types disorders shown by an ECG?

A
  • Disorders of rhythm
  • Disorders of conduction
37
Q

What are the 3 different traces shown by disorders of conduction?

A
  • 1st degree block
  • 2nd degree block
  • 3rd degree block
38
Q

What effect does 1st degree block have on an ECG?

A

Time between P wave and QRS complex much longer

39
Q

What effect does 2nd degree block have on an ECG?

A
  • Sometimes no conduction
  • Some P waves followed by no QRS complex
40
Q

What effect does 3rd degree block have on an ECG?

A
  • No QRS complex generated directly by P wave
  • QRS complex strange shape as it is innervated by a different pacemaker
41
Q

What are the 3 disorders of rhythm?

A
  • Atrial flutter
  • Atrial fibrillation
  • Ventricular fibrillation
42
Q

What is shown by an atrial flutter

A

150 bpm HR

43
Q

What is shown by atrial fibrillation?

A
  • No coordinated P waves
  • Random atrial depolarisations
44
Q

What is shown by ventricular fibrillation

A

No coordinated QRS complex

Systems 2: Cardiovascular (19 decks)

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