Lesson 18: Topic 14 - Electrocardiogram and Cardiac Cycle Flashcards
(50 cards)
what is an ECG signal?
measurement of electrical signal in the heart
- sum of all cardiac action potentials (ventricular and atrial)
the electrical activity in the ECG is predominantly coming from?
the cardiac muscle cells because the atrial APs are too small
what is the P-wave in an ECG?
P wave is when you have atrial depolarization
what does the time length of the P-wave mean?
there is cell-to-cell conduction
- prolonged sengment
what is cell-to-cell conduction?
one cardiac muscle cell is going to depolarize and then the next through the gap junctions and sodium influx
what is the PR segment of the ECG?
- happens after atrial depolarization
- atria contraction
why is there a delay from P to PR on the ECG?
electrical signal reaches AV node and there is going to be a delay in the AV node
what is the purpose of the PR delay segment? (AV node delay)
purpose is to ensure that the atria fully contracts and is able to fully eject the blood from the atria into the ventricle before the ventricle begins to contract
what is the QRS-complex on the ECG?
ventricular depolarization
why does the QRS complex occur very quickly (ventricular contraction)?
the ventricular contraction have purkinje fibers that is going to rapidly excite the whole entire ventricle because we can’t afford to have cell-to-cell conjunction
why is there a large amplitude different in the ventricle contraction (QRS) compared to the atria contraction (P)?
this is because the ventricular contraction is stronger and its stronger because there are more cardiac muscle cells
more cardiac muscle cells =
more electrical activity
what does the ST segment of the ECG represent?
ventricular contraction
- the ventricle is going to contract and eject blood into the aorta and pulmonary artery and then is followed by ventricular repolarization
what does the T-wave of the ECG represent?
ventricular repolarization
what does the TP interval represent in the ECG?
ventricular relaxation and filling
since the T-wave represents ventricular repolarization, where does atrial repolarization happen?
during the QRS complex, its just hidden because the ventricular depolarization is stronger
during an ECG recording, the QRS complex is observed to be smaller than normal. what is the most likely physiological explanation for this change in amplitude?
less electrical activity happening in the ventricle than normal
- less electrical activity = less cardiac muscle cells
- means there are thinner and less cardiac muscle cells in the ventricle
what is systole?
ventricular contraction
what is extrasystole?
premature ventricular contraction
- happening at the wrong time
if we see a huge disruption(meaning big amplitude) in the ECG, what can we assume the chamber causing it is?
we can assume its the ventricle because the atria cannot produce that much electrical signal due to low strength
when looking at ventricular fibrillation, how do we know the problem is occurring in the ventricle?
there is no QRS, so there is no ventricular depolarization properly (not sufficient for a strong contraction, not ejecting blood)
what happens if ventricular fibrillation keeps occuring?
someone will die because there is no blood going to the brain
what can fix ventricular fibrillation?
paddles
- restart the heart and synchrony
what is a complete heart block?
SA node is working properly to sync and cause atrial depolarization
- P-wave is depolarization at a regular sequence but we have the QRS that is out of sync
- PQRST segment is not happening in sync
- PROBLEM: AV node has its own pace making ability to make the ventricle contract, so SA and AV node are both working. the problem is BETWEEN them. the communication is not working
