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BB Cardiovascular Review > 2 - Cardiac Contraction > Flashcards

2 - Cardiac Contraction Flashcards

1
Q

Na+

A

sodium
extracellular = 135-145 mEq/L
RMP intracellular = 14 mEq/L

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2
Q

K+

A

potassium
extracellular = 3.5 - 5.0 mEq/L
RMP intracellular = higher than extracellular, 140?

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3
Q

What does the positive ion concentration gradient result in (RMP)?

A

positive ion concentration gradient frominsidethe membrane to theoutside causes electronegativity inside the membrane
*nondiffusable, negative ions left inside

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4
Q

Most important ions involved in membrane potentials of nerve and muscle cells…

A

Na+, K+ & Cl-

-determines voltage of membrane potential

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5
Q

Cl-

A

chloride
96-106 mEq/L
during RMP, more extracellularly than intracellularly

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6
Q

What prevents all potassium from leaving intracellular compartment during RMP?

A

electrostatic force

-as more K+ leaves (chemical force), negative forces on inside increase and trap K+ (electrostatic)

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7
Q

Nernst Equation

A
  • The diffusion potential level across a membrane that exactly opposes the net diffusion of a particular ion through the membrane is called theNernst potentialfor that ion-
  • electric potential vs. chemical potential
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8
Q

Does any Na+ enter cell during RMP?

A

yes, small but finite leakage, depolarizing effect

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9
Q

Goldman Equation

A
  • calculates membrane potential

- need Na+, K+ and Cl- involved

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10
Q

Normal nerve fiber permeability to K+ vs Na+

A

-the permeability of the membrane to potassium is about 100 times as great as to sodium

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11
Q

Action Potential: Activation Gate

A
  • activated at -70, -50 mV
  • flips open, allows Na+ to rapidly flow inward
  • same conformational change will close gates, just not as quickly
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12
Q

Depolarization Stage

A
  • sudden permeability of Na+ ions

- polarity is neutralized as positive ions rush inwards

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13
Q

Repolarization Stage

A
  • 10,000th of a second

- Na+ channels begin to close and K+ channels open, reestablishing resting membrane potential

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14
Q

Fast Response Action Potentials

A

Atrial myocardial fibers
Ventricular myocardial fibers
Purkinje fibers

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15
Q

Slow-Response Action Potentials

A

Sinoatrial node
Atrioventricular node
*generated by pacemaker cells - automaticity

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16
Q

Autoarhythmic Cell

A

pacemaker cell, slow-response AP

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17
Q

Fast Response Cells

A
  • not automaticity cells

- other cardiac myocytes

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18
Q

Channels of Action Potential in Cardiac Muscle Cells

A
  1. ) Voltage activated, fast sodium channels

2. ) L-type calcium channels (slow calcium channels)

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19
Q

(RMP) Relative to the outside of a cell is the inside positive or negative in charge?

A

negative charge

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20
Q

(RMP)2. Is potassium higher in concentration inside or outside of a cardiac muscle cell?

A

inside the cell

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21
Q

(RMP) Is sodium higher in concentration inside or outside of a cell?

A

outside the cell

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22
Q

(RMP) What prevents potassium from leaking out of a cell until the concentration is the same on the outside and inside of the cell?

A

electrostatic force

-chemical force makes k want to leave, but electrostatic prevents

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23
Q

(RMP) What ion makes the major contribution to the resting membrane of the cardiac muscle cell?

A

Potassium

24
Q

(RMP) What ion makes a small contribution to the resting membrane potential?

A

Sodium

25
Q

(RMP) What ion pump returns ion concentrations back to baseline?

A

Na+, K+ ATPase pump

26
Q

(RMP) How does the Na+-K+ - ATPase pump contribute to the resting membrane potential?

A

3 Na+ to outside of cell
2 K+ into cell
ATP –> ADP
-electrogenic active transport

27
Q

(AP) What ion moves rapidly into a cell during depolarization?

A

Sodium

28
Q

(AP) What ion exits the cell to restore the baseline electrical charge in a cell during repolarization?

A

Potassium

29
Q

(AP) What restores ion concentrations back to their baseline levels?

A

Na+, K+, ATPase pump

30
Q

(EA) In what part of the heart are Fast-Response Action Potentials (non-pacemaker action potentials) found?

A

Atrial myocardial fibers, ventricular myocardial fibers, purkinje fibers

31
Q

(EA) In what part of the heart are Slow-Response Action Potentials (pacemaker action potentials) typically found?

A

SA
AV
Bundle of His

32
Q

(EA) What are some of the differences between Non-pacemaker and Pacemaker action potentials

A 
non-pacemakers: 5 phases
    RMP = -90 mV --> 20 mV
    depolarize quicker
pacemaker: 3 phases
    RMP = -65 mV --> 10 mV
33
Q

(EA) Describe Phase 0 for fast-response/non-pacemaker cells…

A

Phase 0: depolarization (sodium channels open and change the resting potential of membrane from negative to positive +20 pretty fast

34
Q

(EA) Describe Phase 1 for fast-response/non-pacemaker cells…

A

Phase 1: Partial Repolarization, sodium channels close, potassium channels open and potassium goes out, making the inner membrane negative

35
Q

(EA) Describe Phase 2 for fast-response/non-pacemaker cells…

A

Phase 2: Plateau; fast potassium channels close, calcium channels open allowing for some repolarization and the action potential then plateaus due to permeability to sodium and decreased permeability to potassium

36
Q

(EA) Describe Phase 3 for fast-response/non-pacemaker cells…

A

Phase 3: rapid repolarization: calcium channels close and slow potassium channels open, potassium leaves the cell and membrane potential goes back to negative resting level

37
Q

(EA) Describe Phase 4 for fast-response/non-pacemaker cells…

A

Phase 4: restoration of ionic gradients, return to resting membrane potential

38
Q

Release of a large amount of calcium from the Sarcoplasmic Reticulum is triggered by entry of which ion?

A

calcium

-blocks tropomysin, allows myosin head to meat with actin

39
Q

What is the function of the Sarcoplasmic Reticulum within a cardiac muscle cell?

A

regulated intracellular calcium concentration

40
Q

Which ion is the major determinant of the Resting Membrane Potential in Cardiac cells?

A

potassium

41
Q

What are the phases of Slow Response (Pacemaker) Cells?

A

Phase 4
Phase 0
Phase 3

42
Q

Slow Response (Pacemaker) Phase 4

A

Phase 4: Sodium channels open, slow influx of sodium comes in membrane potential slowly starts to depolarize

43
Q 
Slow Response (Pacemaker) 
Phase 0
A

Phase 0: depolarization calcium channels open, calcium comes in so membrane potential is +10

44
Q 
Slow Response (Pacemaker) 
Phase 3
A

Phase 3 repolarization: calcium channels close, potassium channels open (sodium channels are still open but there is more k leaving than sodium coming in)

45
Q

What are the different refractory periods associated with the cardiac action potentials

A

(ERP) Effective Relative period (no action potential can happen)
(RRP) refractory relative period

46
Q

Automaticity

A

ability that pacemaker cells have to launch their own action potential stimuli

47
Q

What is diastolic depolarization?

A
  • atrial-nodal action potential is slower to develop than ventricular muscle action potential.
  • d/t movement of oins
48
Q

What effects on aspects of diastolic depolarization will cause changes in heart rate?

A

autonomic nervous system

49
Q

Which pacemaker region of the heart is typically dominant

A

SA node

50
Q

What is Overdrive Suppression

A

SA node fires quickest, other pacemaker cells do not fire as well

51
Q

What is a sarcomere?

A

Segment between the two Z lines represents the contractile unit, the sarcomere.

52
Q

Cardiac cells are arranged in a branching network that is known as what

A

Functional syncytium

53
Q

What are T-tubules in a cardiac muscle cell?

A

T- tubules are deep invaginations in the sarcolemma membrane
Permits ion exchange between extracellular and intracellular compartments to occur deep in the myocyte during depolarization and repolarization.

54
Q

What is the Sarcoplasmic Reticulum?

A

Extensive branching network that surrounds the myofilaments, activated by influx of calcium from interstitial fluid during action potential and releases more calcium.

55
Q

What is this process called whereby large amounts of calcium are released from the Sarcoplasmic Reticulum into the cell

A

CICR

Calcium Induced Calcium Release

56
Q

The presence of what ion allows binding between actin and myosin

A

Calcium

57
Q

What is the function of Troponin in the binding between actin and myosin

A

At resting state, inhibits binding of actin and myosin

BB Cardiovascular Review (4 decks)

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