Module 2 Flashcards
bradycardia
tachycardia
> 100 bpm
Spread of electrical excitation
- SA node
- Internodal pathway
- AV node
- bundle of his
- right and left bundle branches
- Purkinje fibers
time of electrical conduction
0.2-0.3 seconds
Increase temp
Various drugs
inspiration
all act to ____ the heart rate
increase
Respiratory sinus arrhythmia
normal occurrence, as a result of inspiration/vagus reflex
Increase parasympathetic influence
decrease sympathetic influence
meds- digitalis
all act to _____ the heart rate
decrease
how does inspiration affect the heart rate?
brief decrease in vagus tone thus increases the heart rate
time for atria to depolarize
0.1 sec
Bachmann bundle aka
anterior pathway- transmits directly to left atria
length of delay at AV node
0.1 sec
fxn to allow atrial kick
Sympathetic NS will ______ delay at AV node
Shorten
S S
Parasympathetic NS will ______ delay at AV node
lengthen
time for ventricle depolarization
0.1 sec
P wave
SA node is depolarized, sends AP throughout atria via internal atrial pathways
1/10 second (wow 0.1 for everything)
conduction delay at AV node
0.1 sec. “PR” or “PQ” INTERVAL- from start of atrial contract to start of ventricle contraction
Q wave
septal depolarization
R wave
ventricular depolarization
S wave
depolarization of pukinje fibers
ST SEGMENT
NO electrical activity
T wave
ventricular repolarization
Segment vs interval
Segment = between waves Interval = include one of both waves
ELEVATED ST segment
potential acute MI, ischemia
DEPRESSED ST segment
potenial ischemia, acute posterior MI
Complete Block
3rd degree
complete disruption of conduction btwn atria and ventricles
Incomplete block
1st - all atrial impulses reach bent ricks but its slow
2nd- some atrial impulse reach ventricle
Many P wave with occasional QRS
EKG of 3rd degree black
Elongated PR interval
EKG of 1st degree block
3:1 block- 3 P follow by 1 QRS
EKG of 2nd degree block
During a complete block what is the pacemaker of the heart
Ventricles
sustain 35-45 bpm
Less deadly that ventricular tachy/fib
Atrial tachycardia (tach)
atrial flutter speed
200-350 action potential (HR) per minute
Atrial flutter risk of _____ from ____
CVA
stasis- clot formation
Atril fibrilation speed
> 300-350 action potentials per minute
EKG characteristics of A-fib
dr stowell had a-fib
chaotic P wave morphology
uncoordinated depolarization
MC arrhythmia encountered in clinical practice
A-fib
AV node and ventricles _____ keep up and __________
CAN NOT
they max out around 200 bp
Ventricular Tach speed
> 100 bpm and > 3 irregular beats (PVCs) in a row
Ventricular Fibrillation
functionally heart can’t act as a pump
MEDICAL EMERGENCY
MC cause of death in MI
V-fib
Cardiac AP- slow response
unstable resting membrane potential
pacemaker cells
Cardiac AP- fast response
stable resting membrane potential
contractile cells
Phase 4 (slow depolarization)
driving force-
(slow depolar)
inc. Na+ into cell, depolarizes membrane via “slow Na+ channels”
at -50mV - inc. Ca++ into cell via “transient Ca++ channels”
Phase 0 (upstroke) (slow depolar)
inc Ca++ into cell
Phase 3 (repolarization) (slow depolar)
inc. K+ out of cell
Phase 0 (upstroke) (fast response)
rapid inc. Na+ into cell
Phase 2 (plateau) (fast response)
initial inc. K+ out of cell
Phase 3 (repolarization) (fast response)
Inc. K+ out of cell
Phase 4 (resting membrane potential) (fast response)
K+ maintain resting membrane potential
Fast response AP exhibit prolonged positive phase with prolonged _____________
period of contraction
Fast response AP exhibit prolonged positive phase with prolonged _____________
period of contraction (ensures adequate ejection time)
Parasymp. response on nodal cells in Atria
promote/prolong K+ efflux out and inhibit Na+ and Ca++ influx into pacemaker cells
Decrease slope/increase duration of phase 4
Primary effect of parasymp. in Atria
Sympathetic action on the heart
Inc. HR, Inc. Contratilit, Inc. relaxation rate
aka less relaxation time
Prolong/ increase Ca++ influx
Sympathetic stimulation
Pacemaker cells
increase slope/decrease duration of phase 4
Vaughan William Classifications:
Class 1
Sodium Channel blockade
Class 1A
1B
1C
Moderate
Weak
Strong
Class 2
Beta Blockade
Class 3
Potassium channel blockade
Class 4
Calcium channel blockade
Elevated K+ levels and cardiac APs result:
Bradycardia
severe hyperK can be rapidly fatal
Elevated K+ levels and cardiac APs result:
Bradycardia
severe hyperK can be rapidly fatal
Phase 2 and 3 (fast response)
hyperkalemia causes and INCREASE in efflux on potassium out of myocardium during repolarization
result= shortened repolarization
Elevated K+ levels and cardiac APs result:
EKG changes
Slowing of conduction: peaked T waves- initial
progression: Widening of QRS interval and ventricular arrhythmias develop
terminal: sine wave pattern
Decrease K+ levels and Cardiac APs result:
result is Tachycardia/arrhythmias
Hypokalemia in ECF will
hypopolarize cell (hard to excite) but the OPPOSITE happens in CARDIAC CELL. they HYPEREXCITE
Hyperexcite Phase 2 and 3 (fast response)
increase ECF will prolong or slow repolarization
EKG changes Dec Potassium
Initial: depression of T wave, elevated U wave
EKG changes Dec Potassium
with marked hyopkalemia
t wave becomes progressively smaller, u wave becomes increasingly bigger
EKG changes Dec Potassium further
ventricular and atria tach, potential v fib
Calcium in cardiac muscle increased then
if large amount of Ca++ was released in cardiac muscle it would be unable to relax