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Cardiovascular I > Intro to CV physiology > Flashcards

Intro to CV physiology Flashcards

1
Q

What is bathmotropy?

A

Excitability or threshold of excitation

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2
Q

What is chronotropy?

A

AP emission frequency or HR

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3
Q

What is dromotropy?

A

AP conduction speed or conductibility

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4
Q

What is inotropy?

A

Muscular contraction force or contractility

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5
Q

What is lusitropy?

A

Diastolic relaxation

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6
Q

What is tonotropy?

A

Distensibility

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7
Q

What is the average range for a cardiac muscle AP?

A

200 to 400 msec

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8
Q

What is the significance of the long refractory period of cardiac muscle?

A

Cannot be tetanized
Prevents fatigue
Allows time for heart chambers to fill

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9
Q

What are the 10 steps of cardiac excitation-contraction coupling?

A
  1. AP enters from adjacent cell
    2.Voltage-gated Ca++ channels open
  2. Ca++ induced Ca++ release from SR through RyR channels
  3. Local Ca++ release causes Ca++ sparks
  4. Summed Ca++ sparks creates a Ca++ signal
  5. Ca++ binds to troponin C initiating contraction
  6. Ca++ unbinds from troponin initiating relaxation
  7. Ca++ is pumped back into SR through SERCA channels
  8. Ca++ is exchanged for Na by NCX antiporter
  9. Na gradient is maintained by Na/K ATPase
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10
Q

What occurs during phase 0 of cardiac muscle AP?

A

Opening of voltage gated Na channels
Transient influx of Na

Rapid depolarization

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11
Q

What occurs during phase 1 of cardiac muscle AP?

A

Closure of voltage gated Na channels - Na influx stops
Opening of voltage-gated transient K channels
K efflux - tiny repolarization

Initial rapid repolarization

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12
Q

What occurs during phase 2 of cardiac muscle AP?

A

Opening of voltage gated L-type Ca channels
Ca influx balances K efflux and triggers Ca release from SR
Contraction

Plateau

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13
Q

What occurs during phase 3 of cardiac muscle AP?

A

Ca channels inactivate slowly - decreasing Ca influx
Increased K efflux through delayed rectifying K channel
Repolarization

Late repolarization

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14
Q

What will occur during phase 3 is Ach is present?

A

Ach activates IKAch and increases K efflux
Increases hyperpolarization

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15
Q

What occurs during phase 4 of cardiac muscle AP?

A

RMP is reestablished at -85 mV

Resting membrane potential

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16
Q

What are the 4 types of K channels in heart muscle?

A

Inward rectifying K+ channel (Ik1)
Transient outward K+ channel (It0)
Delayed rectifying potassium channel (Iks, Ikr, and Ikur)
G-protein activated inward rectifying K current (Girk or IkAch)

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17
Q

What is the inward rectifying K channel?

A

Leaky K channel which closes near the end of depolarization and reopen during repolarization

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18
Q

What is the transient outward K channel?

A

Opens transiently at the end of phase 1 and closes during the middle of plateau/phase 2

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19
Q

What is delayed rectifying K channel?

A

Open slowly during the plateau and then more rapidly near the end of phase 2 to initiate repolarization

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20
Q

What is G-protein activated inward rectifying K current?

A

Channel opens in response to Ach release
Efflux of K to cause further hyperpolarization
Reduces effects of If and Ca channels

21
Q

What occurs during phase 0 of SA node AP?

A

Decreased Ca influx through T-Ca channels
Increased Ca influx through L-Ca channels

22
Q

What occurs during phase 3 of SA node AP?

A

Increased K efflux through voltage-gated K channels

23
Q

What occurs during phase 4 of SA node AP?

A

K channels close
Funny Na channels open – Na influx
Slow depolarization of cell
Near threshold funny channels close and T-Ca channels open
L-Ca channels open at threshold

24
Q

What will occur with selective inhibition of funny Na channels?

A

Decreased HR
No effect on contractility

25
Q

What causes extra systole?

A

A sufficiently strong stimulus during relative refractory period

26
Q

What is the compensatory pause?

A

Missed normal systole from the presence of an extra systole

27
Q

What is post-extra systolic potentiation?

A

Extra volume of blood collected in ventricle during compensatory pause resulting in an increased force of contraction

28
Q

What results in the staircase phenomenon?

A

When stimuli of same strength are applied at short intervals resulting in increase in height of contraction

29
Q

What is the intrinsic firing rate of the SA node?

A

70-80 bpm

30
Q

What is the intrinsic firing rate of the AV node?

A

40-60 bpm

31
Q

What is the intrinsic firing rate of the AV bundle?

A

40 bpm

32
Q

What is the intrinsic firing rate of the Purkinje fibers?

A

15-20 bpm

33
Q

What causes the AV nodal delay?

A

Narrow fiber diameter
Relatively few gap junctions
Slow depolarization due to slow voltage-gated Ca channels

34
Q

What is the purpose of AV nodal delay?

A

Allows time for complete ventricular filling
Maintains ventricular contraction rate in case of A fib

35
Q

What is the conduction rate of the SA node?

A

0.5 m/s

36
Q

What is the conduction rate of the atrial pathways and ventricular muscle?

A

1 m/s

37
Q

What is the conduction rate of the AV node?

A

0.05 m/s

38
Q

What is the conduction rate of the AV bundle?

A

1 m/s

39
Q

What is the conduction rate of Purkinje fibers?

A

4 m/s

40
Q

How does SyNS influence conduction?

A

Increases

41
Q

How do beta blockers influence conduction?

A

Decrease

42
Q

How does PsNS influence conduction?

A

Decrease

43
Q

How does ischemia or hypoxia of the heart decrease conduction?

A

Decrease

44
Q

How does digoxin influence conduction?

A

Decrease

45
Q

How to Ca channel blockers influence conduction?

A

Decrease

46
Q

How does norepinephrine from SyNS work in cardiac muscle?

A

Binds to Beta-1 receptors
Adenyl cyclase increases cAMP increasing PKa
Phosphorylation of membrane Ca channels - increases contractility
Phospholamban stimulates SERCA reuptake into SR - increases HR
Troponin I releases Ca bound to troponin C - quicker relaxation

47
Q

How does Ach from PsNS work in cardiac muscle?

A

Binds to M2 receptors in atria
Inhibits adenyl cyclase
Closure of membrane Ca channels - decreases contractility
Inactivation of SERCA channels - decreases HR
Increases K permeability - hyperpolarization

48
Q

How does ischemia in heart affect conduction?

A

Katp channels open - increased extracellular K
Depolarization
Decreases slope of phase 0
Reduced AP conduction velocity

49
Q

How does acidosis effect myocardial function?

A

Inhibits myofibrillar responsiveness to Ca
Decreases binding of Ca to troponin C
Decreases force of contraction

Cardiovascular I (20 decks)

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