Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
163 Cards in this Set
- Front
- Back
|
Two functions of cardiac cells
|
Contractile, Electrical
|
|
|
Myocardial cells are
|
Contractile
|
|
|
Pacemaker cells are
|
Electrical
|
|
|
Myocardial cell characteristics
|
contractile filaments that slide together when stimulated causing contraction
|
|
|
Atria/Ventricle walls are made of
|
Myocardial cells
|
|
|
What is released when a nerve is stimulated
|
neurotransmitter
|
|
|
Neurotransmitters cross between the end of
|
a nerve and muscle (neuromuscular junction)
|
|
|
Ability of cardiac cells to create an electrical impulse w/out stimulation
|
Automaticity
|
|
|
Hearts normal pacemaker site
|
Sinoatrial node (SA)
|
|
|
Important ions in maintaining automaticity
|
Na+ K+ Ca++
|
|
|
Decreases automaticity
|
Increase in Na+ K+ Ca++
|
|
|
Increases automaticity
|
Decrease in K+ Ca++
|
|
|
Why is cardiac muscle electrically irritable
|
due to ionic imbalance across cell membranes
|
|
|
Ability of cardiac muscle to respond to outside stimulus
|
Excitability (Irratibility)
|
|
|
3 types of stimulas to heart
|
mechanical, electrical, chemical
|
|
|
Ability of cardiac muscle to recieve electrical impulse and conduct it to adjoining cells
|
Conductivity
|
|
|
Affects speed of impulse in conductivity
|
sympathetic, parasympathetic NS and medication
|
|
|
Ability of myocardial cells to shorten in response to an impulse
|
Contractility
|
|
|
Meds that strengthen contractibility
|
Digitalis, Dopamine
|
|
|
Energy travels from
|
Negative to Positive
|
|
|
Flow of electrical charge from one point to another
|
Current
|
|
|
Seperate electrical charges of opposite polarity contain
|
Potential energy
|
|
|
Measurement of potential energy
|
Voltage
|
|
|
In a normal heart, electrical activity occurs due to what
|
Ionic changes within cells
|
|
|
Charged particles
|
Ions
|
|
|
Elements that turn into ions
|
Electrolytes
|
|
|
Main cardiac electrolytes
|
Na+ Sodium K+ Potassium Ca++ Calcium Cl- Chloride
|
|
|
Five phase cycle that reflects difference in concentration of electrolytes across cell membrane
|
Action Potential
|
|
|
Exists due to imbalance of charged particles
|
Potential energy (voltage)
|
|
|
How electrolytes cross cell membranes
|
pores or channels
|
|
|
When a cell is at rest, what ion leaks out
|
K+
|
|
|
Proteins and phosphates inside cell carry what type charge
|
Neg
|
|
|
When inside of cell is more negative it is called
|
Polarized
|
|
|
Difference in electrical charges across cell membrane is called
|
Membrane potential
|
|
|
Electrolytes are moved from one side of cell to another via
|
Pumps
|
|
|
Pumps require _______
|
Energy
|
|
|
Energy to pumps come from
|
Adenosinetriphosphate(ATP)
|
|
|
Energy expended by cells to move electrolytes across cell create
|
flow of current
|
|
|
This flow of current is called
|
Volts
|
|
|
For a pacemaker cell to fire, what must exist?
|
a flow of electrolytes across cell membrane
|
|
|
When a cell is stimulated, cell membrane changes and becomes permeable to
|
Na+ and K+
|
|
|
Major extracellular ion
|
Na+ Sodium
|
|
|
Major intracellular ion
|
K+ Potassium
|
|
|
When cellular channels open ______ rushes in
|
Na+
|
|
|
Na+ causes the cell to become more
|
Positive
|
|
|
What happens on ECG when cell becomes more positive
|
waveform is recorded
|
|
|
Name for cell when it becomes more positive
|
Threshold Potential
|
|
|
When movement of electrolytes cause cell to become more positive what is generated
|
Impulse
|
|
|
Impulses cause a chain reaction to
|
next cell membrane
|
|
|
Movement of impulses causing cells to become more positive is called
|
Depolarization
|
|
|
Eventually this impulse spreads from pacemaker cells to
|
Myocardial cells
|
|
|
Impulse spreads through myocardial layers in what order
|
Endocardium to epicardium (inside-out)
|
|
|
Expected response from depolarization
|
Contraction
|
|
|
When the atria contract what is recorded on ECG
|
P wave
|
|
|
P wave represents
|
Atrial depolarization
|
|
|
When the ventricles contract what is recorded on ECG
|
QRS Complex
|
|
|
QRS Complex represents
|
Ventricular depolarization
|
|
|
Depolarization is an _______ event
|
Electrical
|
|
|
Contraction is a ________ event
|
Mechanical
|
|
|
What happens after the cell is depolarized
|
quickly startes to recover and restore electrical charge back to -
|
|
|
Restoring cell back to - charge is called
|
repolarization
|
|
|
In repolarization the cell stops the flow of _____ into cell and allows ____ to leave
|
Na+, K+
|
|
|
Cell returns to _______ in repolarization
|
negative
|
|
|
In repolarization, the contractile proteins do what
|
seperate and relax
|
|
|
Repolarization occurs within layers of heart from ______ to ________
|
epicardium (out) to endocardium (in)
|
|
|
On the EKG, what represents ventricular repolarization
|
ST segment and T Wave
|
|
|
ACTION POTENTIAL
Five phases of Action Potential |
0,1,2,3,4
|
|
|
What do these phases reflect
|
sequence of voltage across cell
|
|
|
Phases 1,2,3 are called
|
electrical systole
|
|
|
Phase 4 is called
|
Electrical diastole
|
|
|
Phase 0 represents
|
depolarization
|
|
|
Phase 0 on EKG is represented by what
|
QRS complex
|
|
|
Cells of atria, ventricle and purkinje fibers contain many ______ channels
|
Na+
|
|
|
SA and AV nodes have ____ Na+ channels
|
Few
|
|
|
If Na+ channels are blocked or slowed, what happens with heart
|
decresed HR and conductivity
|
|
|
4 Phases of cardiac action potential
|
Early repolarization, Plateau Phase, Final Rapid Repolarization, resting Membrane Potential
|
|
|
Na+ channels partiall close, Cl- enters, K+ leaves resulting in decrease electrical charge within cell
|
Early Repolarization
|
|
|
Ca++ enters cell, more K+ leaves allowing sustained contraction
|
Plateau Phase
|
|
|
Plateau Phase represented by what on EKG
|
ST segment
|
|
|
ST segment reflects
|
early part of repolarization of L/R ventricles
|
|
|
What can shorten ST segment
|
Hypercalcemia
|
|
|
K+ leaves cell quickly, Na+ and ca++ channels close and cell becomes more neg
|
Final Rapid Repolarization Phase 3
|
|
|
Phase 3 is represented by what on EKG
|
T Wave
|
|
|
What could cause a longer action potential in Phase 3
|
Blocked K+ channels
|
|
|
Excess Na+ inside cell, excess K+ outside cell...pump activated to send Na out and K in
|
Resting Membrane Potential Phase 4
|
|
|
Period of recovery that cells need after being discharged before they can respond again
|
Refractory period
|
|
|
The refractory period in the heart lasts longer than the
|
Contraction
|
|
|
In what period will the cell not respond at all to stimulus
|
Absolute refractory period
|
|
|
On the EKG, the absolute refractory period is during
|
Onset of QRS to peak of T wave
|
|
|
Period when cells have repolarized to threshold and can be stimulated to respond to stronger than normal stimulus
|
relative refractory period
|
|
|
Relative refractory period corresponds with what on EKG
|
Downslope of T wave
|
|
|
When cells can be stimulated by weaker than normal stimulus
|
Supernormal Period
|
|
|
Supernormal period on EKG
|
end of T wave
|
|
|
What period do arrythymias usually develop
|
Supernormal period
|
|
|
3 Refractory periods
|
Absolute, Relative, Supernormal
|
|
|
CONDUCTION SYSTEM:
Primary pacemaker site in heart |
SA node
|
|
|
SA Node rate
|
60-100 bpm
|
|
|
SA node artery originates from
|
R Coronary artery 60% people
Circumflex 40% |
|
|
Path of impulse from SA node
|
r atria, interatrial septum, l atria
|
|
|
Impulse spreads to AV node via
|
3 Internodal pathways
Bachmans Bundle - anterior Wenkenbachs Bundle-middle Thorels Pathway-posterior |
|
|
Conduction through AV node begins before/after atrial depolarization is complete
|
before
|
|
|
Pathway that conducts impulse to L atria
|
Bachmans Bundle
|
|
|
AV Junction consists of
|
AV node and non branching portion of Bundle of His
|
|
|
Conduction Pathway
|
SA Node, Internodal pathways, AV Junction, Bundle of His, R/L Bundle Branches, Purkinje Fibers
|
|
|
AV junction Rate
|
40-60 bpm
|
|
|
Ventricular Rate (purkinje)
|
20-40 bpm
|
|
|
Speed of conduction impulse is fastest in
|
Bundle of His and Purkinje Fibers
|
|
|
Speed of conduction impulse is slowest in
|
AV and SA nodes
|
|
|
Primary delay in spread of impuls from atria to ventricles occurs in
|
atrionodal and nodal areas of AV node
|
|
|
Arrythmias (abnormal rhythms) are caused by what 3 things
|
increased automaticity, triggered activity or re-entry
|
|
|
When non-pacemaker cells begin to depolarize or pacemaker site other than SA increases firing rate
|
Enhanced automaticity
|
|
|
Enhanced automaticity rhythms
|
atrial flutter, afib, SVT, V tach, V fib, junctional tachycardia
|
|
|
Causes of enhanced automaticity
|
Epi, Atropine, Digitalis toxicity, Electrolyte disturbances
|
|
|
Abnormal electrical impulses when cells are normally quiet
|
Triggered Activity
|
|
|
Triggered activity requires
|
a stimulus
|
|
|
Causes of triggered activity
|
Medications, decreased Magnesium, hypoxia
|
|
|
Beat originating outside SA node is called
|
Ectopic
|
|
|
Spread of impulse through cell already stimulated
|
Reentry
|
|
|
REeentry requires what 3 things to happen
|
potential conduction circuit (accessory pathway), block in circuit and a delayed conduction through remainder of circuit
|
|
|
Cause of Reentry
|
Hyperkalemia
|
|
|
An AV block is a rhythm disturbance associate with a
|
conduction disturbance
|
|
|
Standard Limb Leads
|
I , II, III
|
|
|
Lead I Positive Electrode is on ______arm, Neg electrode on ____arm
|
Left arm, right arm
|
|
|
Lead I views ________surface of heart
|
lateral
|
|
|
Lead II Pos Electrode is on _____ and Neg is on _____
|
Left Leg and Right arm
|
|
|
Lead II views ______ surface of heart
|
Inferior
|
|
|
Lead III Pos electrode is on _____ and Neg is on ______
|
Left Leg, Left arm
|
|
|
Lead III views _____ surface of heart
|
Inferior
|
|
|
Augemented Limb Leads
|
aVR, aVL and aVF
|
|
|
All augmented leads are _____ electrodes
|
Positive
|
|
|
Placement of augmented leads
|
aVR - right arm
aVL - left arm aVF - left leg (foot) |
|
|
Chest Leads
|
V1-V6
|
|
|
All chest leads place are _____ electrodes
|
Positive
|
|
|
The _______ is the neg electrode for chest leads
|
Heart
|
|
|
V1 and V2 placement
|
V1 right side of sternum
V2 left side of sternum fourth intercostal space |
|
|
V1 and V2 view _______ surfaceof heart
|
Septum (down the middle)
|
|
|
V3 and V4 placement
|
V3-betweeen V2 and V4
V4-midclavicular line-5th intercostal space |
|
|
V3 and V4 view _______ surface of heart
|
Anterior
|
|
|
V5 V6 placement
|
left anterior and left midaxillary 5 intercostal space
|
|
|
V5 and V6 view the ______ surface of heart
|
Lateral (low side view)
|
|
|
Bipolar leads consist of
|
a neg lead and a positive lead
|
|
|
Unipolar leads consist of
|
a positive lead and a reference lead
|
|
|
In bipolar leads the right arm electrode is always _____ and the left leg electrode is always
|
negative;positive
|
|
|
ECG paper: small box =
|
.04 sec
|
|
|
Large box =
|
.20 sec
|
|
|
1 small box is ____mm high
|
1
|
|
|
1 large box is ____mm high
|
5
|
|
|
P wave represents
|
atrial depolarization
|
|
|
Straightline recorded when electrical activity is not detected
|
Baseline (isoelectric line)
|
|
|
Movement away from the baseline in either pos/neg direction
|
Waveform
|
|
|
line between waveforms
|
segment
|
|
|
waveform and segment
|
interval
|
|
|
several waveforms
|
complex
|
|
|
Normal characteristics of P Wave
|
Smooth, rounded upright 1:1 to qrs
|
|
|
QRS complex represents
|
Ventricular depolarization
|
|
|
Normal characteristics of QRS complex
|
R always pos S always neg less than .10 sec
|
|
|
T Wave represents
|
Ventricular repolarization
|
|
|
Normal characteristics of T wave
|
slightly asymetric, less than 5mm tall
|
|
|
Neg T waves suggest
|
Myocardial ischemia
|
|
|
Tall, pointed T waves suggest
|
hyperkalemia
|
|
|
low amplitude T waves suggest
|
hypokalemia, hypomagnesia
|
|
|
Deep inverted T waves suggest
|
subarachnoid hemorrage
|
|
|
Tall broad spiked t waves suggest
|
pacemaker
|
