Exam 4 Lecture 2 Flashcards by Nic Stroud

Deep to Superficial in Heart: Layers of heart involved in AP

Endocardium - Myocardium - Epicardium - Pericardial Space - Parietal Pericardium - Fibrous Pericardium

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Superficial to Deep in Hear: Layers of heart involved in AP

Fibrous Pericardium - Parietal Pericardium - Pericardial Space - Epicardium - Myocardium - Endocardium

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Normal Depolarization in the Ventricles: Which direction?

Deep to Superficial

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Normal Repolarization in the Ventricles: Which direction?
* + or - deflection?

Superficial to Deep
* + deflection

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Normal Vrm in a PM cell in the SA node?

-55 mV

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Normal Threshold in PM cell in SA node

-40 mV

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Where does the R Vagus nerve terminate?

SA Node

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Where does the L vagus nerve terminate?

AV node

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Where in the heart does the PNS mostly innervate?
*Which NTM

The nodal area [ACh]

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Where in the heart does the SNS innervate most?
* What NTM and where else can it innervate

Atrial/Ventricular Muscle Tissues [NE]
*Can also innervate the nodal areas, but is out strengthened by ACh

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Why is the Ventricular Myocyte considered a Fast AP?
*What is the normal Vrm

Phase 0 is straight up and down/rapid onset
*-80 mV

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What lead is the normal EKG we see?

Lead 2

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Why is the SA node the PM of the heart?

The tissue at the SA node tends to depolarize and spread the AP faster than other cells in the heart

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Per lecture, what is a normal HR?

72 b/min

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What is the charge of the tissue if the inside is all + and outside is all -?
*Vice Versa

0 mV
*0 mV

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L - R, + to - Depolarization: + or - charge

+ charge always

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L-R, - to + Repolarization: + or - charge

charge always

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R - L, - to + Repolarization: + or - charge?

+ charge always

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Which combination of + and - charges within a tissue produces the most amount of current?

Half + and Half - charges

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What happens if you flip the anode and cathode in the electrical tissue experiment?

The graph will look the same, just flipped across the X axis

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Where is Lead 1 placed?
*What does this cause in terms of AP

+ electrode in L arm or L chest
*depolarization wave towards electrode in L arm/chest

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R to L repolarization causes what in the EKG?

+ deflection in the T wave

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What is the 1st structure in the heart to fully depolarize?

Interventricular Septum

How do Beta Agonists/Antagonists regulate HR?: In General

Change the slope of Phase 4

How does mACh-R regulate HR?: In general

Change Vrm

How does Ca++ regulate HR?: In general

Change threshold potential

How does a Beta Agonist [NE] increase HR? *AC, cAMP, HCN *Time in P4, Slope of P4 *Na, Ca, K, AP rate

Increase AC, Increase cAMP, increase HCN channels = decreases time in Phase 4 = increases/Steepens P4 slope = increases Na and Ca, increasing AP rate and HR; decreases K+ permeability

PM cell: *Vrm *Threshold

*-55 mV *-40mV

How does mACh-R lower HR? *P4 slope compared to Beta Agonist, Vrm *AC, cAMP, HCN *K+

Same slope, but decreased Vrm = longer time to reach AP *decreased AC, cAMP, HCN *Increased K permeability

How does a Beta Antagonist decrease HR? *AC, cAMP, HCN *Time in P4, Slope of P4 *Na, Ca, K, AP rate

Decrease AC, Decrease cAMP, Decrease HCN Decrease P4 Slope [less steep], Increase time in P4 Decreased Na/Ca, increased K permeability Decrease AP rate = less b/min

What happens if you give atropine? *Vrm, AP *K

increased Vrm = shorter time to reach AP *Decreased K permeability

What is HCN: How does it respond to ions *What does it stand for *When is it opened *What ions come in, in order

Hyperpolarization Cyclic Nucleotide: non-cation specific *Opens when the cell is reset via repolarization or hyperpolarization, or increases in cAMP *Na+ first, Ca++ second, K third

How does decreased plasma Ca++ effect HR [hypocalcemia] *Tell me about the CG

Increased HR, b/c threshold potential is more (-), so able to reach AP faster * Decreased CG

How does increased plasma Ca++ effect HR [hypercalcemia] *Tell me about the CG

Decreased HR, b/c threshold potential is more (+), so takes longer to reach AP *Increased CG

Give me a Threshold potential that would be synonymous with Hypocalcemia

Between -55 mV and -40 mV

Give me a Threshold potential that would be synonymous with Hypercalcemia

> -40 mV, to an extent

In what Phase do HCN channels open in SA node PM cells?

Phase 4

Compare the P4 slope in SA Node compared to Purkinje FIber?

Greater/steeper

Name 3 Ways how the HR is regulated?

Change slope of P4, Change Vrm, Ca++

How does Ca++ change the HR? *Where is this mechanism only located

Unknown why it does this and only in heart muscle

In what 2 states do we have constant depolarization in an area of the heart? *Where does injury of current occur

Ischemic/Infart *In areas where we shouldn't have or when we shouldn't have current

What is a ventricular myocyte?

A ventricular muscle cell

What is the P-Wave in terms of Heart function *How long is a normal PR interval, per lecture picture

Atrial Depolarization * 0.16 sec

How many mV is a normal QRS complex? *How many large boxes?

1.5 mV *3 large boxes

A pt comes in with End-Stage COPD, what would you expect to see in their EKG? *Why

QRS <1.5 mV *Air is not conductive to electricity

What is the T-Wave in terms of Heart function *What is the amplitude of the T-Wave, per lecture picture

Ventricular Repolarization - Superficial to Deep *0.3 mV (positive deflection)

Why is the T-Wave a positive deflection?

The epicardium repolarizes before the endocardium

Per lecture, what are the names of the K+ channels located between Phase 0-Phase 3 of a cardiac AP? *What causes these to close

Inward rectifying K+ channels *Increased Na and Ca permeability cause these to close

Per lecture, what is important for the force of heart contractions?

Extension of the AP

Where do we lose most of our voltage during an AP?

Body tissue

Increased Tissue Resistance = ? voltage in heart? *More scar tissue from what cells?

Decreased voltage in heart = possible HB's *Fibroblasts and stem cells

What is the different between Vrm and Threshold Potential in a normal ventricular myocyte

100 mV

A trauma Pt comes in with a pneumothorax; how would you describe their QRS complex in terms of mV

probably <1.5 mV

You noticed you had Lead 1 on the R arm of the Pt, how would you see their EKG?

It would be flipped to the other side [think a/b what he said flipping the cathode and anode. It would be opposite]

A pt comes in with severe facial twitching and arm spasms. How would their cardiac action potential be different compared to a typical, healthy adult?

Their threshold potential would be decreased, leading to an increase in AP, hence the chvostek and trousseau signs

What phases do HCN open?

Phase 4 and 3, most likely