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Cardio 1 > Phys - cardiac muscle > Flashcards

Phys - cardiac muscle Flashcards

1
Q

The prevent tetany of cardiac muscle contraction ___

A

The duration of contraction is roughly the same as the duration of the AP

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2
Q

Cardiac contractility the is an increase in force generation due to ___

A

Altered Ca kinetics

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3
Q

The phase 2 plateau of the cardiac myocyte AP is related to a balance between ___

A

Movement of K out and Ca in

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4
Q

Function of phospholamban

A

Decrease Ca reuptake

*to increase Ca reuptake you must phosphorylate phospholamban

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5
Q

NE increases cardiac contractility by ___

A

Phosphorylation L-type Ca channels

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6
Q

Cardiac relaxation requires ___

A

Removal of Ca from cytosol
ATP to break actin-myosin bond
Membrane repolarization

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7
Q

Atrial vs ventricular transmission of impulses

A
  • Atria have end to end and side to side (horizontal intercalated discs). No t tubules.
  • Ventricles have end to end (perpendicular intercalated discs)
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8
Q

Cardiac AP:

Phase 4

A

Equilibrium for K (-90mV)

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9
Q

IK1

A

Inward rectifying K current

-responsible for stable, low resting membrane potential

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10
Q

Cardiac AP:

Phase 0

A 
Rapid depolarization 
Due to Na channels and then Ca channels
gNa - rapid increase (conductance) 
-H gates are open 
-also have Ca channels, L and T both open
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11
Q

Ca channels closing

A

CaT close early

CaL close late

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12
Q

Cardiac AP:

Phase 1

A
  • K repolarization is due to K outflow and Cl inflow

- Ito1 and Ito2 open rapidly and close rapidly, leads to phase 2

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13
Q

Cardiac AP:

Phase 2

A

Plateau

-relatively equal movement of positive charges in and out of the cell

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14
Q

Cardiac AP:

Phase 3

A

Ca channels close so repolarization takes place, membrane potential drops, and then you get the relative refractory period

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15
Q

In phase 3, m gates are ___ and h gates are ___

A

Closed (mid phase 3)

Opening (towards end of phase 3)

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16
Q

The absolute refractory period takes place during phase ___ because ___

A

2, the inactivation gates of Na channels are closed

-the m gates start to close and the H gates are also closed so the channel is inactivatable

17
Q

The relative refractory period takes place during phase ___ because ___

A

3, h gates start to open

18
Q

In the vulnerable period ___

A

The smallest of stimuli can cause an AP, after phase 3 (aka supranormal period)

19
Q

H gate positions during each phase?

M gates?

A

0- both open
1, 2- m open, h closed
3- m closed, h opening
4- m closed, h open

20
Q

T tubules:

atria vs ventricles

A

Atria have little or none

Ventricles have a lot

21
Q

What causes Ca release from the SR?

A

Trigger Ca from the extracellular space coming in and binding with RYR channels

22
Q

How to speed up Ca reuptake

A

Phosphorylation of phospholamban which activates SERCA

  • positive lusitropic effect (relaxation)
  • inhibiting the inhibitor
23
Q

SERCA

A

Pumps Ca back into SR

-removes Ca from sarcoplasm

24
Q

___ breaks the actin-myosin bond

A

ATP

25
Q

Repolarization of the membrane is due to

A

K efflux

26
Q

Passive tension prior to contraction

  • due to what?
  • what determines it in cardiac muscle
A

Preload

  • due to series and parallel elastic elements
  • end diastolic volume and pressure (as blood comes into the heart the ventricle stretches. The end-diastolic volume is the volume in the ventricle right before it contracts)
27
Q

Active force after contraction

-what is it in the heart?

A

Afterload

-pressure ventricle pumps against (aortic/diastolic pressure)

28
Q

Internal shortening, but no external shortening in the heart

A

Isovolumic (no change in ventricular volume)

29
Q

Cardiac muscle ejection (stroke volume) is what type of muscle contraction?

A

Auxotonic

  • really it is isotonic
  • let’s just call it a shortening contraction
30
Q

Frank starling law of the heart

A

Blood stretches the heart, increased by venous return, increased preload, more force, more ejection, greater stroke volume.

31
Q

The inotropic state of the myocardium determines force generation

A

Contractility

*its all about the amount of Ca in the cytosol

32
Q

Heavier load = ____

A

Slower muscle shortening

33
Q

Increasing cardiac contractility is called a ___

A

Positive inotropic effect

*phosphorylation of phospholamban, RYR channels, and L type Ca channels in the membrane ALL increase Ca levels

34
Q

Epinephrine and norepinephrine cause a ____ inotropic effect
What else does this?

A

Positive

  • beta 1 agonists, sympathetic stimulation
  • MORE Ca IN THE CYTOSOL
35
Q

A change in contractility also can change ___

A

Vmax
Maximum isometric force
*both increase

Cardio 1 (14 decks)

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