Electrophysiology Flashcards
Diffusion of potassium ions out of the cell through selective potassium channels in the cell membrane
Resting membrane potential
Normal resting potential in most myocardial cell
True of atrial, ventricular cells
80-90 mV, cell interior negative
-80 - -90
SA cells, AV nodes, HIS - Purkinje resting membrane potential?
Less compared to atrial and ventricular cells because they have higher permeability to Na and Ca (ions will enter agad)
Do not exhibit a constant resting potential
Voltage-gated ion channels
Opening and closing of channels is dependent on the charge of the membrane (prior to opening)
Brought about by the opening and closing of the Na , K, and Ca ion channels
Na: fast ion channel
K: higher concetration inside than outside, slow ion channel
Action Potential
Action Potential Phases
Phase 1: Early Repolarization Phase
Phase 2: Plateau Phase
Phase 3: Rapid Repolarization Phase
Phase 4: Resting Membrane Potential
More negative
Rapid onset
Fast response
Potential in what cells?
Atrial and ventricular cells
Low resting membrane potential Shorter duration of action potential Less negative Fast sodium channel is inactivated Only the Ca ion goes in and causes the conductance
Pacemaker cells
What ion potential present in these cells?
Skeletal
Cardiac
Sodium ion channel
Sodium and calcium ion channels
Membrane properties of cardiac cells
-Allows us to function
Refractoriness
Membrane responsiveness
Impulse conduction
Membrane property
Membrane cell is insensitive to stimulus
Can’t be stimulated
Refractory
Cardiac cell can’t be stimulated
Needs time to recover
Importance?
Prevents sustained contraction
Membrane property
Refere to the max rate of rise of the action potential upon excitation
Membrane responsiveness
The faster the Vmax, the more readily it is conducted
Clinical Correlation: Drugs are used to control arrythmias
T or F
The bigger the cell, the faster the conduction of impulses
The smaller the fibers, the faster the conduction
T
F
T or F
Atria contracts ahead of the ventricle (‘pump primer’)
True
Predominant cardiac pacemaker
SA node
Resting potential of SAN
-55 to -60 mV
There is a leakage of sodium ions (the higher the leakage, the faster will be the heart rate)
Ca ion channel
Spontaneous diastolic depolarization
So conductance be transmitted in atrial and ventricular cells
Very large fibers
Transmit electric impulse more rapidly
Purkinje system
Faster the rate of depolarization, faster depolarization of other tissues than self-excitation
What node?
SA
Innervation of the <3
Sympathetic - AV nodes
Norepinephrine
Increases heart rate, contractility, cardiac output
Exercise, emergency
Parasympathetic - Vagus
Acetyl choline
Slowing of the heart rate
Block conduction
Records the electrical impulses of the heart through electrodes placed on the skin
Electrocardiogram
Atrial depolarization
P wave
Ventricular depolarization
QRS
T wave
Ventricular repolarization
True or False
Heart will be depolarized from the right, base
to
left, apex
True
Abnormal rhythmicity of the pacemaker
Arrythmia
Sinus greater than 100 beats per min
Rate less than 60 beats
Sinus tachycardia
Sinus bradycardia
A 3rd degree block
Conduction comes from other pacemaker
Complete Heart Block
Each part of the ventricle stimulated
No effective contraction
Abnormal conduction of the ventricle
Rapid, variable ventricular contraction
Ventricular fibrillation
Treatment: Reboot the <3, defibrillate
