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TV2001 > Cardiac Physiology > Flashcards

Cardiac Physiology Flashcards

1
Q

How many heart chambers do fish have?

A

Two

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2
Q

How many heart chambers do reptiles and amphibians have?

A

Three

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3
Q

How do valves open and close?

A

forwards flow opens them and backwards flow closes them

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4
Q

How is eversion of the hart valves prevented?

A

chordae tendinae, attached to papillary muscles of the ventricles

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5
Q

Describe the characteristics of Myocardial cells

A
  • excitable, striated, branches, mononucleated with abundant mitochondria.
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6
Q

How are myocardial cells joined together?

A

gap junctions (allows passage of ions)

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7
Q

How are action potentials able to spread quickly between cells?

A

intercalated discs allow myocardium to contract as a coordinated unit

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8
Q

What are the two types of cardiac muscle cells?

A
  1. Contractile cells (99%)

2. Autorhythmic cells/ pacemaker cells

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9
Q

Why are Autorhythmic cells important in the heart?

A

heart does not rely on nervous input to generate an action potential.

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10
Q

Where are Autorhythmic cells found in the heart?

A

found in SA and AV nodes, as well as conduction pathways

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11
Q

What happens in Phase 4 (Pre-potential) of the action potential at the SA Node?

A
  1. i(f) channels open
  2. inward Na current
  3. Depolarisation
  4. Opening of transient Ca++ channels (i(Ca))
  5. more depolarisation
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12
Q

What happens in Phase 0 (Rapid depolarisation)

A

opening of long lasting voltage gated Ca channels at threshold potential (-40mV)

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13
Q

What happens at Phase 3 (Repolarisation)

A
  1. Opening of K+ channels and closure of Ca channels

2. as membrane reaches -65mV, i(f)Na channels start to open again for Phase 4

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14
Q

In what order are the conducting centres (in order of speed)

A
  1. SA node
  2. AV node
  3. AV bundle
  4. Purkinje fibres
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15
Q

What affect does Acetylcholine have on the SA node?

A
  • released from parasympathetic nerves
  • Causes slow rate of rise of pacemaker potential (prolongs Phase 4).
  • decreases HR
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16
Q

What affect does Catecholamine have on the SA node?

A
  • released from sympathetic nerves and adrenal medulla
  • act via beta-1 receptors on heart muscle to increase rate of polarisation in phase 4
  • increase HR
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17
Q

What is the significance of the AV node?

A

delays the signal from the SA node and allows time for ventricular filling

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18
Q

What are the 5 phases of Contractile Cell action Potential

A
  • Phase 0 (Rapid Depolarisation)
  • Phase 1 (initial rapid repolarisation)
  • Phase 2 (Plateau phase)
  • Phase 3 (rapid repolarisation)
  • Phase 4 (rest phase)
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19
Q

What happens in Phase 0 of Contractile Cell action Potential?

A

opening of voltage gated Na channels (i(f))

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20
Q

What happens in Phase 1 of Contractile Cell action Potential?

A

opening of transient K+ channels (i(k)(t))

21
Q

What happens in Phase 2 of Contractile Cell action Potential?

A

Opening of long lasting Ca channels (L-Type) (iCaL)

22
Q

What happens in Phase 3 of Contractile Cell action Potential?

A

K+ efflux due to opening of voltage gated K+ channels (i(k)

23
Q

What is a refractory period?

A

occurs after initiation of action potential in an excited membrane and lasts until the action potential ends

24
Q

What is the significance of the length of a refractory period?

A

a shorter period allows the muscle to maintain sustained contraction (e.g. skeletal muscle)

25
Q

What is the sequence of events in contraction coupling in cardiac muscle?

A
  1. action potential enters from adjacent cell
  2. voltage gated Ca++ channels open, letting Ca++ in.
  3. Ca++ causes release of CA++ from SR via ryanodine receptor channels
  4. local release of Ca++ causes Ca++ spark
  5. Ca++ sparks create Ca++ signal
  6. Ca++ binds to troponin causing contraction of muscle
  7. relaxation when Ca++ unbinds from troponin
  8. Ca++ pumped back into SR for storage
  9. Ca++ exchanged for Na in ECF
  10. Na+ gradient is maintained by Na+-K+-ATPase
26
Q

What physiological process is interrupted by foxglove poisoning?

A

Contraction of cardiac muscle

27
Q

What affect does sympathetic activity have on the heart?

A

increases activity by increasing Ca++ influx

28
Q

What is represented by the P wave?

A

Atrial depolarisation

29
Q

What is represented by the QRS complex?

A

ventricular depolarisation

30
Q

What is represented by the T wave?

A

ventricular repolarisation

31
Q

Why is atrial repolarisation not seen on an ECG?

A
  1. slow process
  2. obscured by the QRS complex
  3. a much smaller muscle, so only makes a very small wave
32
Q

What is shown by the PR interval?

A

duration of impulse from SA node to ventricles

33
Q

What is shown by the QT interval?

A

ventricular depolarisation and repolarisation

34
Q

What is shown by the RR interval?

A

one full cardiac cycle

35
Q

List the main types of Arrhythmias

A
  • sinus arrest
  • sinus brady
  • sinus tachy
  • conduction block (1st, 2nd, 3rd degree block)
36
Q

What is 1st degree AV block?

A

longer PR interval

37
Q

What are the two types of 2nd degree AV Block?

A

Mobitz Type 1 and Mobitz Type 2

38
Q

What is Mobitz Type 1?

A

PR intervals increase until AV node fails and no QRS wave is seen

39
Q

What is Mobitz Type 2?

A

No QRS complex. requires a pacemaker

40
Q

What is 3rd degree AV Block?

A
  • complete conduction block

- no impulse goes through AV node, atrium and ventricle are in complete isolation and beat at their own intrinsic rate

41
Q

What factors can cause ectopic pacemaker activity?

A
  • toxins
  • electrolyte imbalance
  • ischemia
42
Q

What is ectopic pacemaker activity?

A

frequency of action potentials is too high and coordinated contraction of myocardial cells isnt possible

43
Q

What is Atrial Fibrilation?

A
  • continuous random passage of action potentials through the atria
  • ## irregular RR, no P wave
44
Q

What is a complication of Atrial Fibrillation?

A

blood pools in atrium, causing clots

45
Q

What is Ventricular Fibrillation?

A
  • continuous random passage of action potentials through the ventricles (electrical chaos)
  • emergency, requires CPR and defibrillation
46
Q

What is Systole?

A

period of contraction/ ejection

47
Q

What is Diastole?

A

period of relaxation/ filling

48
Q

What can be seen on a Wigger’s diagram?

A

ECG, Heart sounds, pressure lines, ventricular volume, positions of valves, phase of cardiac cycle

TV2001 (21 decks)

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