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AHN 568 Unit 1 Questions with
Detailed Verified Answers
Sinoatrial Node (SA node)
Rate?
Location & Area of intervention?
EKG? Answer: 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? Answer: 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? Answer: pathway for electrical signals to be
transmitted to the ventricles
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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? Answer: 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 Answer: SA
node
Interatrial tracts
AV node
Bundle of His
Bundle branches
Purkinje fibers
resting membrane potential Answer: Electrical charge of
cardiac muscle cells at rest
Depolarization Answer: 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 Answer: recharging of a cell to its normal
polarity; K+ allows for repolarization
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action potential Answer: 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? Answer: Calcium
Phase 4 Answer: Phase 4: Resting State
Na+ and Ca2+ channels are closed; increase in K+
permeability to allow for a new cycle
Phase 0 Answer: Phase 0: Rapid depolarization
Opening of voltage-gated fast Na+ channels; cell fires to
initiate transmission of electrical impulse
Phase 1 Answer: Phase 1: Depolarization
Peak positive charge; K+ closes, Cl- enters to slow channels,
slow Ca2+ channels open
Phase 2 Answer: 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 Answer: Phase 3 Re-polarization
Opening of voltage-gated K+ channels and closing of Ca2+
channels; K+ moves from ICF to ECF
Refractory periods Answer: time from phase 0 until the
repolarization of a myocyte or when enough Na+ have
recovered
AHN 568 Unit 1 Questions with
Detailed Verified Answers
Sinoatrial Node (SA node)
Rate?
Location & Area of intervention?
EKG? Answer: 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? Answer: 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? Answer: pathway for electrical signals to be
transmitted to the ventricles
, Page | 2
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? Answer: 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 Answer: SA
node
Interatrial tracts
AV node
Bundle of His
Bundle branches
Purkinje fibers
resting membrane potential Answer: Electrical charge of
cardiac muscle cells at rest
Depolarization Answer: 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 Answer: recharging of a cell to its normal
polarity; K+ allows for repolarization
, Page | 3
action potential Answer: 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? Answer: Calcium
Phase 4 Answer: Phase 4: Resting State
Na+ and Ca2+ channels are closed; increase in K+
permeability to allow for a new cycle
Phase 0 Answer: Phase 0: Rapid depolarization
Opening of voltage-gated fast Na+ channels; cell fires to
initiate transmission of electrical impulse
Phase 1 Answer: Phase 1: Depolarization
Peak positive charge; K+ closes, Cl- enters to slow channels,
slow Ca2+ channels open
Phase 2 Answer: 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 Answer: Phase 3 Re-polarization
Opening of voltage-gated K+ channels and closing of Ca2+
channels; K+ moves from ICF to ECF
Refractory periods Answer: time from phase 0 until the
repolarization of a myocyte or when enough Na+ have
recovered
