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UCLA EKG Study WITH 100- COMPLETE ANSWERS
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10/10/24, 6:46 AMEUNICE
UCLA EKG Study WITH 100% SURE ANSWERES
Terms in this set (68)
The inside of the heart cell has a higher potassium concentration, whereas the
outside has a higher concentration of sodium.
What does it mean when the heart is • The higher positive charge outside the cell causes a relatively more negative
electrically polarized at rest? charge inside the cell.
• The difference between the charges outside and inside of the cell wall is known as
its electrical potential.
Na+ moves into the cell rapidly in response to an electrical impulse: Inside of cell
loses negative
potential.
What occurs during depolarization within
the heart cell?
Depolarization is propagated from cell to cell, transmitted across the entire heart.
• The wave of depolarization represents a flow of electricity.
What happens in repolarization of the The ions return to their original resting state and the heart cells restore their resting
heart? polarity.
Phase 0: Na+ flow in and rapid depolarization occurs
when stimulated
List in phases the electrophysiology of the Phase 1: Rapid return to isoelectric level
heart Phase 2: Ca++ ions flow in and myocytes contract
Phase 3: K+ flow out and rapid depolarization occurs
Phase 4: Polarized resting phase
Allow the heart to integrate electrical and mechanical
activity of the heart
Name the three different type of heart cells 1. Pacemaker cells
2. Electrical conduction cells
3. Myocardial cells
Pacemaker cells have the ability to initiate an impulse
(automaticity)
o Sinoatrial (SA) node:
What do pacemaker cells do?
o Atrioventricular (AV) node
o Purkinje fibers
o Every cell in the heart has automaticity, but normally suppressed.
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What do the electrical conduction cells Wires of the heart's electrical circuit
do? • Carry current rapidly and efficiently to distant regions of the heart
What is electrical pathway of the heart Sinoatrial (SA) node ->Internodal pathways ->Atrioventricular (AV) node->Bundle of
starting from SA node His->Bundle branches -> Purkinje fibers
SA (Sinoatrial) Node • Located in the right atrium near
the superior vena cava
• Primary pacemaker • Inherent rate: 60-100 bpm • Innervated by autonomic nervous
system
What is the pathophysiology of the SA
• Electrical impulses from SA node
node
"depolarizes" the atria via
internodal tracts and
Bachmannn's bundle, resulting in
atrial contraction.
AV (Atrioventricular) Node • Located in the inferior right
atrium
• Responsible for slowing down
What is the pathophysiology of the AV
conduction from the atria to the
node?
ventricles just long enough for
atrial contraction to occur
• Subsidiary pacemaker • Inherent rate: 40-60 bpm
Divides into the right and left bundle branches
What is the pathophysiology of the bundle
• Impulses are conducted down the LBB faster than the RBB. The difference in
of HIS?
conduction time allows both ventricles to contract at the same time.
Purkinje Fibers • Finger-like projections that extend
from the bundle branches
What is the pathophysiology of the Purkinje
• Send impulses into the myocardial tissues of the
fibers?
ventricles and causes them to contract
• Subsidiary pacemaker • Inherent rate: 20-40 bpm
The contractile machinery of the heart
• When a myocardial cell is depolarized,
calcium is released within the cell,
What do the myocardial cells do?
causing the cell to contract.
• Myocardial cells transmit an electrical current,
but far less efficient.
• SA node (• 60-100 bpm)
What are the SA, AV, and purkinje rates? • AV node (• 40-60 bpm)
• Purkinje fibers (• 20-40 bpm)
Na: 135-146 mEq/L
• K: 3.6-5.3 mEq/L
What are the normal electrolyte levels for
• Ca: 8.5-10.3 mg/dL
sodium, K, CA, ionized CA, Mg?
• Ionized Ca 1.09-1.29 mmol/L (Corrected:1.10 mmol/L)
• Mg: 1.4 - 1.9mEq/L
Monitors electrical currents created by impulses in the
heart through electrodes attached to the skin
Purpose of EKG • Shows the sequence of electrical events
• Doesn't show the heart's mechanical activity or
pumping ability
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