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Human Physiology - Cardiopulmonary Physiology > Cardiac electrophysiology and ECG > Flashcards

Cardiac electrophysiology and ECG Flashcards

1
Q

why is it important that the coronary arteries are on the surface of the muscle

A

so they are not compressed upon contraction

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2
Q

what structures drain blood from the upper and lower body into the right atrium

A

upper - superior vena cava
lower - inferior vena cava

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3
Q

what does it mean that the heart has variable pump output

A

flow is not always the same

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4
Q

how many pulmonary veins are there

A

4
2 from each lung that converge before the heart

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5
Q

what allows cardiac action potentials to propagate from cell to cell

A

gap junctions

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6
Q

what is the duration of a normal cardiac action potential
what mediates this

A

250 ms
voltage gated Ca2+ channels allowing leading to a plateau phase of the AP

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7
Q

what is the resting membrane potential of cardiac muscle cells

A

-85 mV

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8
Q

what structures form gap junctions
what happens if there are genetic deformities of these proteins

A

connexons
mutations are incompatible with life

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9
Q

what are the specialised conductive tissues in the heart (in order)

A

SA node
AV node
bundle of His
left and right bundle branch
Purkinje fibres

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10
Q

automaticity of heart cells

A

ability to generate a heart beat without nervous system input

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11
Q

what electrically isolates the atria and ventricles

A

annulus fibrosus ?
hearts fibrous skeleton - fibrous rings

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12
Q

where does electrical activity normally originate in the heart
what is the pacemaker potential of these cells

A

SA node
-70mV

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13
Q

why does the SA node depolarise before the AV node

A

it has a higher pacemaker potential (less negative)

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14
Q

what forms the only site of electrical connection between the atria and ventricles

A

AV node

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15
Q

what is the rate of SA pacemaker potential
why is heart rate different to this

A

~90 - 100 bpm
parasympathetic tone slows natural rhythm

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16
Q

chronotropic agents

A

agents that alter heart rate

17
Q

examples of positive chronotropic agents and their receptors

A

adrenaline and noradrenaline
beta-adrenergic receptors

18
Q

examples of negative chronotropic agent and its receptors

A

acetylcholine
muscarinic cholinergic receptors

19
Q

effect of ANS on the membrane potential of the SA node

A

sympathetic: increases the potential (more rapid depolarisation)
parasympathetic: decreases the potential

20
Q

what controls the movement of electrolytes through gap junctions

A

free movement only controlled by concentration gradients

21
Q

what is an ECG

A

recording of electrical activity of the heart from the body surface using electrodes to allow a spatial perspective of electrical events

22
Q

why do an ECG

A
  • suspect disturbances in rhythm and conduction
  • localise and assess extent of ischemic damage
  • assess size of chambers
  • assess effects of changes in electrolyte concentrations
23
Q

how does the flow of electrical signals provide the recording we see in the ECG

A

electrical vectors parallel to the axis of the lead result in maximal deflection
vectors perpendicular to axis result in 0 deflection
vectors travelling towards the exploring electrode (+) result in a +ve deflection
vectors travelling away from + electrode result in -ve deflection

24
Q

p wave

A

atrial depolarisation

25
Q

QRS complex

A

ventricular depolarisation

26
Q

t wave

A

ventricular repolarisation

27
Q

P-R interval

A

time between atrial and ventricular depolarisation due to AV node conduction block

28
Q

ST segment

A

plateau phase of ventricular action

29
Q

what part of an ECG is important in diagnosis of ventricular ischemia or hypoxia

A

ST segment

30
Q

Q-T interval

A

time for both ventricular depolarisation and repolarisation
roughly estimates the duration of an average ventricular AP

31
Q

what does ST elevation indicate

A

myocardial infarction
think “STEMI”

32
Q

what does ST depression indicate

A

myocardial ischemia

33
Q

what does a sinus dysrhythmia ECG show

A

varied R-R intervals with normal sinus rhythm

34
Q

what does a atrial fibrillation ECG show

A

irregularly irregular, often rapid, absent P waves, and erratic, fibrillatory waves between QRS complexes.

35
Q

what does left ventricular hypertrophy ECG show

A

increased QRS voltage, particularly in the left precordial leads (V5, V6)

may also display signs like a left axis deviation and ST-T wave abnormalities.

Human Physiology - Cardiopulmonary Physiology (4 decks)

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