EKG Flashcards
What is the cardiac cycle?
cycle of contraction and relaxation
What is an ECG/EKG
a recording of electrical events in the heart
How does an EKG relate to conduction?
an EKG shows how well conduction is working and will show any deviations from normal conduction
How are conductile cells different from contractile cells?
conductile cells transmit signals and contractile cells contract to pump blood
Describe action potential at the SA node
Define prepotential aka pacemaker potential
gradual upward drift showing depolarization (increase) of the membrane potential
Why is it important for the heart to have a long absolute refractory period?
the relaxation of the heart allows the heart to fill up with blood. If the heart was in constant contraction, it wouldn’t pump blood
Parts of an EKG
P wave, QRS complex, T wave, PR interval, QT interval, QRS interval, PQ segment, ST segment
What does the P wave of an EKG represent
atrial contraction (depolarization)
What does the QRS complex of an EKG represent
ventricular depolarization
What does the T wave of an EKG represent
ventricular repolarization
What does the PR interval of an EKG represent
signal conduction through AV node before activating ventricles
What does the QT interval of an EKG represent
duration of ventricular depolarization; shorter during exercise
What does the QRS interval of an EKG represent
atrial repolarization and diastole; repolarization concealed by QRS wave
What does the PQ segment of an EKG represent
signal conduction from SA node to AV node; atrial systole begins
What does the ST segment of an EKG represent
ventricular systole and ejection of blood; corresponds to plateau of cardiomyocyte action potential
What can we learn from an EKG?
deviations from normal can help diagnose abnormalities
Cardiac arrhythmias definition
abnormality in rhythm or force of the heartbeat
Describe tachycardia
fast heart rate at rest
Describe bradycardia
slow heart rate at rest
Describe atrial fibrillation
chaotic depolarizations that do not stimulate ventricles; common in elderly and alcoholics
Describe a heart block
failure of any part of the conduction system to conduct signals
Describe premature ventricular contraction
ventricular ectopic focus with extra beat
