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The Cardiac Pressure-Volume Cycle Flashcards

1
Q

If is what type of channel?

A

HCN
hyperpolarisation activated, cyclic nucleotide gated channel

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2
Q

Some ion channels are voltage gated. Some are —- dependent.

A

time
open or close with a delay

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3
Q

Two K+ channels to know for cardiac cycle?

A
  • inward rectifier K+ channels
  • delayed rectifier K+ channels
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4
Q

Inward rectifier K+ channels

A
  • open when Vm goes below -60mV
    • unusual, most open when cells
      are at rest
  • function: to clamp membrane
    potential (Vm) at rest
  • lets K+ out of cell, repolarising it
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5
Q

Delayed Rectifier K+ channels

A
  • opens when membrane
    depolarises
  • but both opening and closing takes
    place with a delay
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6
Q

Basic action potential:

A
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7
Q

Example of a positive feedback loop in depolarisation:

A

Na+ enters cell, causing more depolarisation causing more Na+ channels to open, causing more depolarisation

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8
Q

At rest what occurs in action potential:

A
  • *** inward rectifier K+ channels are
    open
  • K+ leaving cell is dominant current
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9
Q

Depolarisation stage of action potential

A
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10
Q

Repolarisation stage of action potential:

A
  • *** delayed rectifier K+ channels
    open
  • Na+ channel inactivation, decrease
    in Na+ entry into cells
  • Delayed Rectifier K+ channels open:
    increase in K+ going out

Vm less positive!!!

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11
Q

After hyperpolarisation stage of action potential:

  • insert diagram
A

insert slide

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12
Q

What channels are open in the stages of action potential?

A
  • baseline/rest: inward K+ channels
    open, very few Na+
  • depolarisation: inward K+ close,
    Na+ opens
  • repolarisation: Na+ channels close,
    Delayed rectifier K+ open
  • after hyperpolarisation: Delayed
    rectifer close, inward K+ open
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13
Q

Refractory period of an action potential

A
  • amount of time it takes a cell membrane to be ready for a second stimulus after reaching resting state
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14
Q

Ventricular Myocyte action potential phases name:

A
  • phase 0
  • phase 1
  • phase 2
  • phase 3
  • phase 4
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15
Q

Cardiac action potential is ——– than skeletal

A

broader

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16
Q

Ventricular myocyte action potential: phase 0:

insert diagram: where is P0?

A
  • depolarisation
  • Na+ channels open with positive
    feedback
    insert diagram
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17
Q

Ventricular myocyte action potential: phase 1:

insert diagram: where is P1?

A
  • transient outward current
  • delayed rectifier K+ channels
  • K+ leaves myocyte
  • myocyte starts to repolarise
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18
Q

Ventricular myocyte action potential: phase 2:

insert diagram: where is P2?

A
  • plateau phase
  • Ca1+ channels open: time and
    voltage dependent
  • Ca2+ enters as K+ leaves
  • calcium current into cell just about
    balances the K+ current leaving the
    cell
  • very slow repolarisation in this
    phase
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19
Q

Ventricular myocyte action potential: phase 3:

insert diagram: where is P3?

A
  • rapid repolarisation phase
  • Ca2+ channels that maintain
    plateau close
  • delayed rectifier K+ channels open
  • K+ leaves myocyte
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20
Q

Ventricular myocyte action potential: phase 4:

insert diagram: where is P4?

A
  • resting potential
  • K+ leaves myocyte
  • inward rectifier K+ channels
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21
Q

Comparison of action potentials: which action potential time always stays the same?

A

Nerve cells
1 millisecond

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22
Q

Comparison of action potentials: Middle in terms of action potential length?

A
  • skeletal muscle
  • 2-5 mins
  • contraction follows action potential
  • short refractory period
  • tetany occurs with repeated stimuli
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23
Q

comparision of AP 3 diagram

A

label lines
insert diagram

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24
Q

Comparision of action potentials: cardiac action potential: time:

A
  • varies in size and duration
    depending on requirements
    (exercise)
  • can last upto 500 milliseconds
  • contraction during action potential
  • long refractory period - prevents
    tetany of cardiac muscle!!!
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25
Q

Cardiac action potentials vary in time and shape depending on which part of heart. Which has lowest plateau phase?

A

SA node and AV node

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26
Q

Sinus and AV node cardiac action potentials:

A
  • Pacemaker tissues:
    • spontaneous depolarisation
    • no inward K+ rectifier current
    • not stable at rest
      0 = depolarisation phase
      1 = does not exist
      2 = does not exist
      3 = repolarisation phase
      4 = pacemaker potential

Phase 4 is a pacemaker current: If current = funny current

depolarisation is due to Ca2+ not Na+
no plateau phase as no inward K+ rectifier
repolarisation is due to delayed rectifier K+

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27
Q

If (funny current)

A
  • If increases upon hyperpolarisation
  • HCN channel
  • makes SA node spontaneously
    active
  • If leads to a NET INWARD CURRENT

If involves:
- large Na+ current inwards
- tiny K+ current outward

  • depolarises cell to 0mV
28
Q

What is responsible for cardiac auto-rhythmicity?

A
  • If (funny) current makes the SA node spontaneously active
29
Q

Cardiac myocytes are joined together by

A

intercalated discs

30
Q

Intercalated Discs:

A
  • joins adjacent cardiac myocytes
  • 3 components:
    • desmosome, adherens junctions,
      gap junctions
  • low electrical resistance, high ion
    permeability
  • allows action potentials to easily
    pass from cell to cell
31
Q

Desmosome

A

structural
holds cells together

32
Q

Adheres junctions

A

anchor thin actin filaments to ensure co-ordinated movement

33
Q

gap junctions

A

free ion movement between cardiac myocytes gives the intercalated discs a low electrical resistance and allows the action potential to move freely from cell to cell

34
Q

Functional Syncytium

A
  • syncytium = multinucleated cell
    due to multiple cell fusions eg skeletal muscle
  • 2 functional syncitia:
    - atrial
    - ventricular
  • each follows the all or nothing rule
35
Q

Intercalated discs purpose

A

allow co-ordinated cardiac contraction

36
Q

Conduction Velocities in the heart

A

only connection between atria and ventriculars is the slowest (allows atria to complete contraction)

37
Q

What controls the AV node conduction velocity?

A

autonomic nervous system
acts via effects on phase 0 depolarisation

38
Q

Sympathetic AV node conduction

A

Sympathetic chain

NAdr, beta 1, Gs, increased cAMP,
adenylate cyclase

39
Q

Parasymathetic AV node conduction:

A

Vagal

Ach, muscarinic receptors, Gs, decreased cAMP

40
Q

What drugs and mechanism can slow AV node conduction?

A
  • bisoprolol (beta 1)
  • verapamil (L type Ca2+ channels)
    (CCB)
  • Digoxin (increases vagal tone)
41
Q

Sarcomere

42
Q

Sarcomeres and Starling’s Law

A
  • myocyte stretch increases overlap of thick and thin filaments

-MORE OVERLAP, INCREASES ACTIN MYOSIN CROSS BRIDGING INCREASES FORCE GENERATION

  • hence increases force and duration of contraction
43
Q

Intrinsic regulation of contractile force (starling mech) vs extrinsic regulation (sympathetic stimulation)

A

starling is longer and stronger
sympathetic is faster and stronger, same number of cross-bridges working harder

44
Q

left ventricle pressure

45
Q

aorta pressure

46
Q

Maximum pressure in the left ventricle is different to the maximum pressure in the aorta.

true or false?

A

False; both the same

47
Q

Which pressure is the same during systole?

A

aorta and left ventricle as aortic semi-lunar valve is open

48
Q

Which pressure is the same during diastole?

A

left atrium and left ventricle as mitral valve is open in diastole

49
Q

cardiac cycel diagram

A

insert
with valves opening and closing
isovolumic contracgtion and relaxation

50
Q

Isovolumic contraction period

A

period after mitral valve is closed, and before aortic valve is open, when the ventricle is contracting but there is no change to volume of blood, despite increase in pressure

51
Q

Isovolumic Relaxation period

A

period after aortic valve closes and before mitral valve opens, where the ventricle is relaxing but there is no change in volume despite decrease in pressure

52
Q

4 phases of diastole

A
  • isovolumic relaxation
    (after mitral valve opens and before it closes)
  • passive filling
  • diastasis
  • active filling (+atrial contraction)
53
Q

2 phases of systole

A

Isovolumic contraction and ejection

54
Q

cardiac cycle

55
Q

heart sounds

56
Q

P wave is

A

atrial systole

57
Q

QRST complex is

A

ventricular systole

58
Q

Aortic Stenosis on cardiac cycle draw and shade

59
Q

Wiggers plot of the cardiac cycle

60
Q

Wiggers volume loop of left ventricle

61
Q

Mitral stenosis loop

62
Q

aortic stenosis loop

63
Q

mitral regurg loop

64
Q

aortic regurg loop

65
Q

Which thin filaments are common biomarkers to all muscle and which are specific to cardiac muscle and detail of biomarkers

A

Tn-C common to all
Tn-T cardiac
Tn-I cardia

= Tn-T binds the troponin complex to
tropomyosin
= Tn-C binds Ca2+ during excitation-
contraction coupling
= Tn-I inhibits cross-bridging to
myosin heavy chains

66
Q

CK-MB

A
  • creatine biomarker specific to
    cardiac muscle
  • moves high energy phosphate
  • from ATP in mitochondria
  • to ADP in the cytoplasm
67
Q

Markers of Myocardial damage

A

list the dayys and markers

HLB (49 decks)

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