Innervation + ECG Notes Flashcards
4 cell types in heart
myocardial cells
conduction cells
avascular valvular tissue
endocardial cells
spaces between myocardial/conduction cells are called/function
gap junctions
gateway for impulses to travel from cell to cell
myocardial cells (AKA, perform, where, how many)
contractile cells
perform kinetic work (contraction)
in atrial walls/myocardial layer of ventricle walls
most common
contractile (myocardial) cells must have _____ stimulation to contract, cause by a(n) _____
electrical
action potential
a cardiac cell, AKA _____, consists of units called ____ which consist of even smaller unit called _____
myocyte
myofibrils
sarcomeres
a myofibril contains ___ and ____ which facilitate ___ by _____ and ____
actin
myosin
contraction
sliding apart
together
conduction cells (AKA, what)
auto-arrythmic cells
specialized cells capable of initiating an electrical impulse
do not have the ability to contract
endocardial cells
line inner surfaces of the heart, including each of the 4 heart valves
action potential
electrical discharge caused by ion movement
involves depolarization and repolarization cycles
key ions of an action potential
Calcium (CA++)
Potassium (K+)
Sodium (NA+)
Ca++ cause
myocyte contraction by coming into the cell
K+ causes
repolarization of myocyte when exiting cell
Na+ causes (except when)
ion movement produces cell-to-cell conduction (of depolarization) in the heart
except AV node (depends on slow movement of Ca++ ions)
resting cells are ___ charged (____)
negatively
polarized
depolarized cells have a ___ charge
positive
depolarization causes
myocardial contraction
intrinsic innervation what/how it depolarizes
internally motivated journey of electrical impulses through the heart and back
depolarizes at natural pacemaker and repolarizes in reverse sequence
SA node (what, where, initiates, creates, pulse rate)
dominant pacemaker
upper wall of RA
initiates wave of depolarization along internodal paths
creates sinus rhythm
pulse rate of 60-100 bpm
AV node (what, acts, location, function)
only pathway between atria/vent
act as back up pacemaker if SA node fails (pulse 40-60bpm)
just above tricuspid valve in RA
depolarization slows here = allows time for atria to contact/blood enter vemt
Bundle of His (location, function)
slightly distal to AV node
depolarization. speeds up again shooting through LT/Rt bundle branches
RT/LT bundle branches (what, impulses travel, creates)
2 separate bundles of much smaller Purkinje fibers
impulses travel along interventricular septum towards the apex, then turns sup toward base f lateral sides of the heart
ventricular myocytes depolarize = creates QRS complex
Purkinje Fibers (what, deliver, function, location)
branch off bundle branches
deliver impulses to individual muscle cells
can generate back up pulse rate of 30-40 bpm (still need pacemaker)
edge of endocardium and expand to epicardium
repolarization starts with ____cardium going to ____cardium
epi
endo
extrinsic innervation
externally motivated control over HR/contractility by symp/psyop nervous systems
chronotropy
heart rate
inotropy
contracility
preload
ventricular filling volumes
afterload
systemic arterial pressure
symp nervous system (runs from, effect, stimulated when, releases)
runs from medulla to thoracic spine level
accelerates heart (release nor-epinephrine, increase ion exchange, increase HR/force of contraction)
stimulated during stress (fight/flight)
psymp nervous system (runs from, effect, stimulated when, releases)
runs from medulla to heart via vagus nerve
slows HR
stimulated during rest
releases acetycholine
deflection ECG
direction - up/down
standard ECH has how many electrodes/leads vs what we use
10/12
3/1
P wave
represents atrial depolarization
first electrical even in normal rhythm
PR segment
represent atrial contraction
flat segment during AV node delay
PR interval
include P wave and PR segment
represents complete atrial activity
QRS complex
represents ventricular depolarization
largest deflection on ECG
shows rapid ventricular conduction
ST segment
represents ventricular contraction
usually appears as isoelectric line
T wave
represents ventricular repolarization
occurs during continued ventricular contraction
QT interval
spans QRS complex to end of T wave
represents complete ventricular systole
