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VET 408: Cardio/Respiratory > Cardiac Cycle > Flashcards

Cardiac Cycle Flashcards

1
Q

phases of a non-nodal action potential

A

phase 0: depolarization (Na entry)
phase 1: rapid repolarization (transient K exit)
phase 2: plateau (Ca entry and K exit)
phase 3: repolarization (K exit)
phase 4: resting membrane potential (Na/K pump and K leaking)

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2
Q

what is excitation contraction coupling

A

process of AP arrival leading to myofibril contraction and relaxation

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3
Q

myofibrils

A

actin and myosin

actin: thin filament
myosin: thick filament

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4
Q

sarcomere

A

functional unit of contraction

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5
Q

cross-bridge cycling

A

ATP dependent process of actin and myosin sliding to shorten the sarcomere

begins with Ca influx

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6
Q

actin-troponin complex

A

tropomyosin fiber wraps around actin and covers the myosin head binding site on the actin –> prevents myosin binding

Ca must bind to troponin to cause tropomyosin to move off of myosin binding site

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7
Q

troponin C

A

binding site for Ca on troponin complex

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8
Q

troponin I

A

inhibits actin-myosin interaction by blocking the binding site

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9
Q

troponin T

A

binds troponin complex to tropomyosin

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10
Q

tropomyosin

A

supports actin and regulates interactions with myosin

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11
Q

L type Ca channels

A

transports Ca from extracellular –> intracellular

opens in response to changes in membrane potential

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12
Q

ryanodine receptors

A

transports Ca from sarcoplasmic reticulum to cytosol

opens in response to Ca influx from L type channels

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13
Q

what is the main source of Ca used for contraction

A

sarcoplasmic reticulum

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14
Q

SERCA

A

sarco-endoplasmic reticulum ATPase

transports Ca from cytosol back into the SR during recovery to allow for relaxation

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15
Q

phospholamban

A

inhibits SERCA to slow down rate of relaxation –> ultimately slows HR and contractility

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16
Q

PMCA

A

plasma membrane Ca ATPase

transports Ca from intra –> extracellular

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17
Q

Na/Ca exchanger

A

transporters Ca from intra –> extracellular

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18
Q

steps of contraction and relaxation of myocytes

A
  1. cell depolarizes from opening of Na channels (phase 0)
  2. extracellular Ca enters through L-type Ca channels (phase 2)
  3. intracellular Ca triggers Ca release from SR via ryanodine receptors
  4. increased cytosolic Ca –> binds troponin C –> pulls tropomyosin off of myosin binding site
  5. actin-myosin cross bridging occurs to cause contraction
  6. SERCA sequesters Ca back into SR
  7. myocyte relaxes
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19
Q

what two factors affect contractility

A

Ca concentration
Ca sensitivity

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20
Q

what mediators and receptors are used in sympathetic stimulation of EC coupling

A

NE and epi
B1 adrenergic receptors

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21
Q

effects of sympathetic stimulation on EC coupling

A

phosphorylation of:
1. L-type channels: phosphorylation increases Ca influx
2. Phospholamban: when phosphorylated, decreases SERCA inhibition –> increased rate of relaxation
3. troponin I –> increases rate of relaxation

NET: increased chronotropy, inotropy, dromotropy, and lusitropy

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22
Q

what mediator is used in parasympathetic stimulation of EC coupling + effects

A

acetylcholine

NET: decreases chronotropy, inotropy, dromotropy, and lusitropy

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23
Q

what is the cardiac cycle

A

sequence of mechanical and electrical events that occur during each heart beat

24
Q

what initiates the cardiac cycle

A

SA node

25
Q

systole

A

contraction and emptying

AV valves: closed (prevent backflow)

SL valves: open

26
Q

diastole

A

relaxation and filling

AV valves: open

SL valves: closed

27
Q

phase 1 of cardiac cycle

A

atrial contraction

occurs at end of diastole to “top off” the ventricles

AV: open
SL: closed

28
Q

pressure during phase 1 of cardiac cycle

A

atrial = ventricular

29
Q

sounds heard during phase 1 of cardiac cycle

A

S4 sound

normal in LA, abnormal in SA

30
Q

phase 2 of cardiac cycle

A

isovolumetric contraction

occurs at start of systole to generate enough pressure to open SL valves

AV: closed
SL: closed

31
Q

pressure during phase 2 of cardiac cycle

A

end diastolic volume

large increase in ventricular pressure

small increase in atrial pressure

32
Q

sounds during phase 2 of cardiac cycle

A

S1 sound - closing of AV valves

normal in all animals

33
Q

phase 3 of cardiac cycle

A

rapid ejection

occurs during systole to push blood out of ventricles

AV: closed
SL: open

34
Q

pressure during phase 3 of cardiac cycle

A

ventricular = aortic pressure

then ventricular pressure decreases as blood exits

35
Q

sounds during phase 3 of cardiac cycle

A

no sound

any sounds heard = flow murmur

36
Q

phase 4 of cardiac cycle

A

reduced ejection

occurs during end of systole to finish contraction via passive flow

AV: closed
SL: open

37
Q

pressure during phase 4 of cardiac cycle

A

aortic pressure slightly > ventricular pressure

both are decreasing
atrial pressure increases slightly as it continues to fill (venous return)

38
Q

sounds during phase 4 of cardiac cycle

A

none

39
Q

phase 5 of cardiac cycle

A

isovolumetric relaxation

occurs during early diastole to begin active ventricular relaxation

AV: closed
SL: closed

40
Q

pressure during phase 5 of cardiac cycle

A

end-systolic volume

ventricular < aortic pressure to cause SL valve closure

increase in atrial pressure

41
Q

sounds during phase 5 of cardiac cycle

A

S2 sound - closure of SL valves

normal in all species

42
Q

phase 6 of cardiac cycle

A

rapid/early filling

occurs during diastole to allow for rapid ventricular filling/atrial emptying

PASSIVE process - majority of filling

AV: open
SL: closed

43
Q

pressure during phase 6 of cardiac cycle

A

atrial pressure > ventricular pressure

44
Q

sounds during phase 6 of cardiac cycle

A

S3 sound

normal in LA, abnormal in SA

45
Q

windkessel effect

A

aortic/arterial blood flow continues even during diastole

aortic walls stretch during systole to store blood; walls contract during diastole to maintain organ perfusion

46
Q

phase 7 of cardiac cycle

A

reduced filling (diastasis)

occurs during diastole; blood flow from atria to ventricles nearly stops

AV: open
SL: closed

47
Q

pressure during phase 7 of cardiac cycle

A

atrial pressure slightly > ventricular pressure

mostly done filling at this point - rest occurs during phase 1

48
Q

sounds during phase 7 of cardiac cycle

A

none

49
Q

wiggers diagram

A

diagrams the change in atrial, ventricular, and aortic pressure during the cardiac cycle

diagram is the same shape of the curve for R and L sides of the heart BUT right is at lower pressures

50
Q

how does right side stroke volume compare to left side stroke volume

A

equal - same amount of blood gets ejected

51
Q

how does right side pressure compare to left side pressure

A

right side < left side

52
Q

what does AV valve closure define

A

the start of systole

53
Q

what does SL valve closure define

A

the start of diastole

54
Q

what is stroke volume

A

the volume of blood ejected from the ventricle in one cardiac cycle

SV = EDV - ESV

EDV: end-diastolic volume (greatest ventricular volume)

ESV: end-systolic volume (lowest ventricular volume)

55
Q

what is ejection fraction

A

the percentage of blood leaving the ventricle with each cycle

EF = SV / EDV
OR
EF = (EDV - ESV) / EDV

VET 408: Cardio/Respiratory (38 decks)

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