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A&P I 2024 > Cardiac (Exam III) > Flashcards

Cardiac (Exam III) Flashcards

1
Q

Contraction strength of cardiac muscle is highly dependent on ________.

A

Extracellular Serum Ca⁺⁺

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2
Q

What is the Vᵣₘ of the SA node?

A

-55mV

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3
Q

What is the Vᵣₘ of the ventricular muscle fibers?

A

-80mV

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4
Q

What is considered a normal healthy heart rate in A&P, as defined in lecture?

A

72 bpm

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5
Q
  • Of all the nodal tissue in the heart, which would be considered as having the slowest action potential?
  • What would have the fastest action potential?
  • What would have an intermediate speed compared to the above?
A
  • SA node
  • Purkinje Fibers (Ventricular Muscle)
  • AV Node or Bundle of His
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6
Q

Which action potential is more affected by K⁺ channel alterations?

A

Nodal tissue action potentials

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7
Q

Membrane permeability of what ion is depicted by 1 on the figure below?
What tissue would you expect to find this permeability chart referring to?

A

K⁺ permeability

Myocardial Muscle Cell

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8
Q

Membrane permeability of what ion is depicted by 2 on the figure below?

A

Na⁺ permeability

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9
Q

Membrane permeability of what ion is depicted by 3 on the figure below?

A

Ca⁺⁺ permeability

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10
Q

What tissue would you expect to find this permeability chart referring to?

A

Nodal Tissue (SA node, AV node)

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11
Q

Membrane permeability of what ion is depicted by 1 on the figure below?

A

Na⁺ permeability

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12
Q

Membrane permeability of what ion is depicted by 2 on the figure below?

A

K⁺ permeability

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13
Q

Membrane permeability of what ion is depicted by 3 on the figure below?

A

Ca⁺⁺ permeability

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14
Q

Lidocaine primarily affects which ion channels? What does this mean in regards to its effects on cardiac action potentials?

A
  • Fast Na⁺ Channels
  • Lidocaine primarily affects ventricular activity
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15
Q

What does Phospholamban do?

A

Regulates flow of Ca⁺⁺ through SERCA pump. Inhibitory at resting conditions.

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16
Q

How much of Ca⁺⁺ used in cardiac contraction comes from the ECF?

A

20%

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17
Q

How much of Ca⁺⁺ used in cardiac contraction comes from the ICF?

A

80%

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18
Q

What is a one-sentence summary of CI-CR ( Ca⁺⁺Induced - Ca⁺⁺Release)

A

CI-CR refers to the concept that Ca⁺⁺ released from the sarcoplasmic reticulum is dependent on Ca⁺⁺ brought in from the ECF.

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19
Q

Where are DHP and RyR1 receptors found in the cardiac muscle?

A

Trick question. Neither of these are in cardiac muscle. We have L-Type Ca⁺⁺ Channels instead.

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20
Q

How many Ca⁺⁺ ions does 1 Calsequestrin store?

A

40 Ca⁺⁺ ions

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21
Q

Why is cardiac muscle more dependent on serum Ca⁺⁺ than skeletal muscle?

A

Internal Sarcoplasmic Reticulum Ca⁺⁺ stores open dependent on external Ca⁺⁺ influx.

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22
Q

What pump is the cornerstone of Vᵣₘ regulation throughout the body?

A

Na⁺ K⁺ ATPase pump

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23
Q

What occurs to intracellular Ca⁺⁺ after a contraction?

A
  • 80% resorbed to SR by SERCA pump.
  • 15% moved to ECF by Na⁺ Ca⁺⁺ Antiporter
  • 5% moved to ECF by Ca⁺⁺ ATPase pump
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24
Q

What three actions does Protein Kinase A (PKA) potentiate in cardiac muscle?

A
  1. Attaches to Troponin I = makes F-Actin sites more available.
  2. Potentiates L-type Ca⁺⁺ channels = ↑ time open and ↓ threshold needed for action potential.
  3. Inhibits Phospholamban = phospholamban inhibition lets SERCA push more Ca⁺⁺ back into SR so it can be used for next contraction.
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25
Q

What drug (aside from sildenafil & milrinone) also has Phosphodiesterase inhibition activity?

A

Caffeine

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26
Q

What receptor potentiates SNS activity in the heart?
Which receptor inhibits SNS activity of the the heart?

A
  • Potentiates = β
  • Inhibits = mACh
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27
Q

What G-protein is used by β receptors for cardiac potentiation?
What G-protein is used by mACh receptors for cardiac inhibition?
What do each of these interact with to produce their effects?

A
  • Gₛ
  • Gᵢ
  • AC (Adenylate Cyclase)
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28
Q

What is necessary to open up Ca⁺⁺ stores of the SR in cardiac muscle?

A

Extracellular Ca⁺⁺

29
Q

Does cardiac muscle still have transverse tubules?

A

yes

30
Q
  • Potentiation of AC (adenylate cyclase) results in what?
  • Inhibition of AC (adenylate cyclase) results in what?
A
  • ↑ AC = ↑ cAMP = ↑ PKA
  • ↓ AC = ↓ cAMP = ↓ PKA
31
Q

What threshold needs to be met for an action potential to occur in the SA node?

A

-40mV

32
Q

What is the Vᵣₘ of the Purkinje fibers?

A

-90mV

33
Q

Decreasing the “slope” or phase 0 of a cardiac myocyte’s action potential would involve which structure?

A

Na⁺ channels

34
Q

What effect would doubling the serum K⁺ levels have on the membrane potential of K⁺ ?

A

↓ Vᵣₘ ( ex. -70mV vs -90mV) (less negative Vᵣₘ)

35
Q

What effect would doubling serum K⁺ levels have on the cardiac action potential of myocardial tissue?

A
  1. ↑ K⁺ = ↓ Vᵣₘ (less negative Vᵣₘ)
  2. ↓ Vᵣₘ = incomplete resetting of Na⁺ channels
  3. Fewer utilized Na⁺ channels = decreased phase 0 slope.
36
Q

Phosphorylation through β-agonism mechanisms makes _________ channels more sensitive.

A

L-Type Ca⁺⁺

37
Q

If one ion’s permeability increases then another ion’s permeability __________.

A

Decreases

38
Q

The slope of which phase dictates heart rate in nodal tissue?

A

Phase 4

39
Q

What occurs during phase 1 & 2 in the SA node’s action potential?

A

Trick question, nodal tissue does not have a phase 1 or phase 2.

40
Q
  • Which cardiac tissue would most likely be greater affected by Calcium Channel Blockers (CCBs) ?
  • What effect would CCBs have on the action potential of this tissue?
A
  • Nodal Tissue
  • ↓ Phase 0 slope
41
Q

Phase 4 is also known as _________ _________.

A

Diastolic Depolarization

42
Q

Is Diastolic Depolarization faster in myocardial tissue or nodal tissue?

A

Nodal Tissue

43
Q

What is causing the phenomenon in Na⁺ permeability denoted by the red line in the figure below?

A

↑pNa⁺ due to Na⁺ sneaking through opening L-type Ca⁺⁺ channels.

44
Q

Which two types of Ca⁺⁺ channels are present in the heart?
Which is more prevalent?
Which have more β activity?

A
  • T & L type Ca⁺⁺ Channels
  • L-type Ca⁺⁺ are more prevalent
  • L-type Ca⁺⁺ have more β activity
45
Q

Is the initial permeability of K⁺ in phase 4 low or high?
When does the permeability of K⁺ get reduced in a cardiac myocyte?
Why is this?

A
  • Relatively high
  • Phases 0, 1, 2.
  • Due to closure of Kᵢᵣ Channels.
46
Q

What are Kᵢᵣ channels?
What happens to the permeability of K⁺ due to these channel?

A
  • Kᵢᵣ ( K⁺ Inward Rectifying) Channels are VG K⁺ channels that exist to close while an incoming current moves across the cell membrane.
  • ↓ pK⁺
47
Q

What are the two purposes of Kᵢᵣ channels?

A
  1. Allows for a ↑ plateau phase.
  2. Prevents K⁺ loss during plateau phase.
48
Q

Compare the phase 4 slopes of nodal tissue and ventricular tissue.

A
  • SA Node phase 4 slope = very steep
  • Ventricular Myocyte phase 4 slope = very gradual
49
Q

Where is permeability of K⁺ greatest in a cardiac myocyte?

A

Phase 3

50
Q

What channels most greatly affect the phase 4 slope of nodal tissue?

A
  • HCN (Hyperpolarization Cyclic Nucleotide) Channels
    also called
  • ifunny or if channels.
51
Q

What sets i-f channels into motion?

A

Hyperpolarization

52
Q

What would β-agonism do to HCN channels?

A

↑cAMP = ↑ HCN channel usage = ↑pNa⁺ = ↑ Phase 4 slope.

53
Q

What mechanic of β-agonism increases HCN channel permeability?

A

↑cAMP

54
Q

How do mACh agonism affect Phase 4 of nodal tissue?
Give an example.

A
  • mACh agonism → ↑pK⁺ → raises Vᵣₘ of cell.
  • Vᵣₘ changed from -55mV to -65mV. Longer time/path to threshold
55
Q

How would atropine affect Phase 4 of nodal tissue?
Give an example.

A
  • mACh antagonism → ↓pK⁺ → lowers Vᵣₘ cell.
  • Vᵣₘ changed from -55mV to -45mV. Shorter time to threshold.
56
Q

Changes in serum Ca⁺⁺ can affect threshold, what would occurs with:
- Hypercalcemia?
- Hypocalcemia?

A
  • ↑ threshold of activation
  • ↓ threshold of activation
57
Q

Changes in serum Ca⁺⁺ can affect phase 4 slope, what would occurs with:
- Hypercalcemia?
- Hypocalcemia?

A
  • ↑ Ca⁺⁺ = ↓ pNa⁺ = decreased phase 4 slope
  • ↓ Ca⁺⁺ = ↑ pNa⁺ = increased phase 4 slope
58
Q

Changes in phase 4 slope are dependent on what ion?

A

↑ or ↓ of pNa⁺ ( a little bit of Ca⁺⁺ )

59
Q

In nodal tissue, increased permeability of Ca⁺⁺ and Na⁺ cause decreased permeability of K⁺ via ______.

A

Kᵢᵣ (K⁺ inward rectifying) channels.

60
Q

When do Kᴛᴏ (Transient Outward) channels open?

A
  • At the peak of Phase 0 and comprise phase 1
61
Q

The opening of what channels cause the initial repolarization noted in phase 1?

A

Kᴛᴏ (Transient Outward) channels

62
Q

What phase is the shortest in a cardiac myocyte?

A

Phase 0

63
Q

What structure bridges cardiac myocytes and increases surface area available for gap junctions?

A

Intercalated discs

64
Q

What is the innermost layer of the heart?

A

The endocardium

65
Q

What is the outermost layer of the heart?
What are its characteristics?

A
  • Fibrous Pericardium
  • Tough and stiff
66
Q

What are the layers of the heart going from most superficial to most deep?

A
  1. Fibrous Pericardium
  2. Parietal Pericardium
  3. Pericardial Space
  4. Epicardium
  5. Myocardium
  6. Endocardium
67
Q

What would binding of ACh do to the SA and AV node of the heart?

What is the mechanism of this?

A

↓ HR by ↑ pK⁺

( mACh GPCR bound by ACh opens K⁺ channels allowing K⁺ to flow out of the cell)

There is no β-agonist equivalent.

68
Q

What potentiates HCN (ifunny channels)?
What is the result?

A
  • cAMP
  • ↑ phase 4 slope

A&P I 2024 (18 decks)

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