Physiology-Surface ECG Flashcards
What is the end goal of an action potential in the heart?
To allow Ca2+ to enter the cell, causing muscle to contract.
Where does the cardiac action potential originate?
Sinoatrial node. It has the fastest nodal pacemaker.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/071/884/437/a_image_thumb.jpg?1659415999)
What autonomic nerves stimulate the heart to either increase or decrease heart rate?
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![](https://s3.amazonaws.com/brainscape-prod/system/cm/071/884/438/a_image_thumb.jpg?1659415999)
How is the SA node related to the graph illustrated below?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/071/884/439/q_image_thumb.jpg?1659454284)
The SA node action potential initiates atrial contraction. The illustration depicts the Frank-Starling Mechanism: the strength of ventricular contraction is dependent on the end diastolic volume…which is dependent on atrial contraction.
What would happen if the AV node did not have as slow of conductance as it does?
The atria would contract before all of its contents have been emptied.
Where does the action potential propagate after the AV node?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/071/884/441/q_image_thumb.jpg?1659454284)
Down the His-Purkinje system -> working ventricular myocardium from apex to base and endocardium to epicardium.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/071/884/441/a_image_thumb.jpg?1659415999)
Why is AV node conductance slow and the His-Purkinje system fast?
The AV node has slow Ca2+ channels that results in a slow rise in phase 0. The His-Purkinje system utilizes fast Na+ channels.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/071/884/442/a_image_thumb.jpg?1659416000)
Why do epicardial cells tend to repolarize before the endocardial cells?
The epicardial cells have a shorter action potential duration
![](https://s3.amazonaws.com/brainscape-prod/system/cm/071/884/443/a_image_thumb.jpg?1659416000)
What factors contribute to positive, negative and zero deflections in ECG readings?
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![](https://s3.amazonaws.com/brainscape-prod/system/cm/071/884/444/a_image_thumb.jpg?1659416000)
What are the standard leads used in an ECG?
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![](https://s3.amazonaws.com/brainscape-prod/system/cm/071/884/445/a_image_thumb.jpg?1659416000)
What are the different bipolar leads in an ECG?
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![](https://s3.amazonaws.com/brainscape-prod/system/cm/071/884/446/a_image_thumb.jpg?1659416001)
What are the different unipolar leads in an ECG?
You use “Wilson’s central terminus” by using the heart as the central negative electrode. By removing one electrode, you measure the voltage by assessing the voltage of the other two electrodes in its absence.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/071/884/447/a_image_thumb.jpg?1659416001)
What happens when you put the bipolar and unipolar leads together in an electrocardiogram?
The leads give you a hexaxial reference system with axis oriented in 30 degree increments around the heart.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/071/884/448/a_image_thumb.jpg?1659416001)
What is the purpose of having unipolar precordial leads?
They provide a hexaxial reference system in the horizontal plane.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/071/884/449/a_image_thumb.jpg?1659416001)
What wave occurs at this point in an ECG?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/071/884/450/q_image_thumb.jpg?1659454284)
The P-wave. The SA node leads to atrial depolarization which causes a positive vector production in lead I and the avF lead.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/071/884/450/a_image_thumb.jpg?1659416002)