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AHN 568 Unit 1 Questions and Answers 2024/2025 $13.49   Add to cart

Exam (elaborations)

AHN 568 Unit 1 Questions and Answers 2024/2025

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  • AHN 568
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  • AHN 568

Sinoatrial Node (SA node) Rate? Location & Area of intervention? EKG?  Natural pacemaker of the heart Rate: 60-100 bpm Location: Upper portion posterior portion of the Right Atrium near superior vena cava EKG: represented as the P wave Atrioventricular node (AV node) Rate? Location? �...

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  • October 10, 2024
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  • 2024/2025
  • Exam (elaborations)
  • Questions & answers
  • AHN 568
  • AHN 568
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AHN 568 Unit 1 Questions and Answers
2024/2025
Sinoatrial Node (SA node)

Rate?

Location & Area of intervention?

EKG?

 Natural pacemaker of the heart
Rate: 60-100 bpm

Location: Upper portion posterior portion of the Right Atrium near superior vena cava

EKG: represented as the P wave




Atrioventricular node (AV node)

Rate?

Location?

 A specialized mass of conducting cells located at the atrioventricular junction in the
heart. (back-up pacer of the heart
Rate 40-60 bpm

Location: Near the tricuspid valve




Bundle of HIS

Rate?

Location?



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 pathway for electrical signals to be transmitted to the ventricles
Rate: 40-45 bpm

Location: partially in right atrium and upper portion of interventricular septum that connects

the AV node and 2 bundle branches




Purkinjie Fibers

Rate?


 hair-like fibers that spread out from bundle branches into the ventricles; innervate
myocardial cells directly; initiate ventricular depolarization
Rate: 20-40 bpm




Normal Conduction Pathway through the Heart


 SA node
Interatrial tracts

AV node

Bundle of His

Bundle branches

Purkinje fibers




resting membrane potential


 Electrical charge of cardiac muscle cells at rest


Depolarization




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 change in the electrical charge of a stimulated cell from negative to positive by the
flow of ions; Na+ allows for depolarization, except in AV node which depends on the
slow moving Ca2+


Repolarization

 recharging of a cell to its normal polarity; K+ allows for repolarization


action potential

 as cardiac cells reverse polarity, the electrical impulse generated during that event
creates an energy stimulus that travels across the cell membrane


What ion causes contraction?


 Calcium


Phase 4

 Phase 4: Resting State
Na+ and Ca2+ channels are closed; increase in K+ permeability to allow for a new cycle




Phase 0

 Phase 0: Rapid depolarization
Opening of voltage-gated fast Na+ channels; cell fires to initiate transmission of electrical

impulse




Phase 1

 Phase 1: Depolarization
Peak positive charge; K+ closes, Cl- enters to slow channels, slow Ca2+ channels open




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Phase 2

 Phase 2 Plateau
Opening of voltage gated slow Ca2+ channels and closing of some K+, some Na+ enters to

maintain; membrane potential is maintained or plateaued




Phase 3

 Phase 3 Re-polarization
Opening of voltage-gated K+ channels and closing of Ca2+ channels; K+ moves from ICF to

ECF




Refractory periods

 time from phase 0 until the repolarization of a myocyte or when enough Na+ have
recovered


Absolute refractory periods


 occurs with the early part of the T-wave when most of the ventricle is depolarized and
is "refractory" to new stimuli


Relative refractory periods

 occurs towards the end of the T-wave when most ventricular cells are repolarized and
vulnerable to new stimuli; can lead to VT if PVC lands during this time
Refractory = resistant




Normal P Wave

 Measures: 0.5 - 2.5mm high
< 0.12 secs in width



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