Cardiac Depolarization
Cardiac Depolarization - Related Videos
03:06
Investigating Prolonged Depolarizing Afterpotential (PDA) in Drosophila Photoreceptors
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2025
This video demonstrates an experimental protocol to investigate the prolonged depolarizing afterpotential (PDA) in white-eyed Drosophila. The fly's eye is exposed to intense blue light pulses to convert the photopigment rhodopsin to metarhodopsin, initiating a signaling cascade that opens positive ion channels and causes membrane depolarization. Because blue light prevents the reconversion of metarhodopsin to rhodopsin, the continuous influx of positive ions results in sustained depolarization,...
01:19
Depolarizing Blockers: Pharmocokinetics
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2023
Depolarizing blockers are administered through intravenous injection. Succinylcholine is the most common choice of depolarizing blockers in emergency clinical practices. Although they have a rapid onset, they readily diffuse away from the motor end plate into the extracellular fluid. They are metabolized by enzymes such as liver butyrylcholinesterase and plasma pseudocholinesterases. This produces a short duration of action, typically 5-10 minutes long, unlike nondepolarizing blockers, which...
01:28
Depolarizing Blockers: Mechanism of Action
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2023
Depolarizing blockers act on skeletal muscle fibers' membranes and induce their depolarization. Most depolarizing blockers have two quaternary N+ atoms that bind the nicotinic acetylcholine receptors and cause neuromuscular blockade within minutes. Succinylcholine is the most commonly used depolarizing blocker. Chemically, it constitutes two molecules of acetylcholine joined together by an acetate methyl group. They act on the receptors in the same way as acetylcholine. Because succinylcholine...
08:25
Visualization of Streptococcus pneumoniae within Cardiac Microlesions and Subsequent Cardiac Remodeling
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Cited by 11 •
2015
Streptococcus pneumoniae forms discrete non-purulent microscopic lesions in the heart. Outlined is the protocol for a murine model of cardiac microlesion formation. Instruction is provided on microlesion visualization using microscopy, discrimination between early and late microlesions, and methods to detect cardiac remodeling in hearts of convalescent animals.
07:06
Combining Imaging and Electrophysiology to Visualize and Record Spreading Depolarizations in Mice
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2024
This protocol demonstrates the combination of imaging and electrophysiology to reliably detect spreading depolarizations in adult mice following a mild traumatic brain injury.
FAQs
The principal distinction is the inward current that drives phase 0. In atrial and ventricular myocytes, opening of voltage-gated fast sodium channels produces rapid sodium influx. Sinoatrial and atrioventricular nodal cells instead rely mainly on calcium entry through L-type calcium channels. This cellular difference gives pharmacology a basis for analyzing why an intervention may affect working-muscle conduction and nodal activity differently.
The cell type being studied determines which channel mechanism is most relevant. In atrial and ventricular myocytes, pharmacological interpretation centers on fast sodium-channel opening during phase 0. In sinoatrial and atrioventricular nodal cells, interpretation centers on L-type calcium-channel entry. Keeping these contexts separate helps distinguish effects on myocardial conduction from effects on nodal electrical behavior.
Antiarrhythmic drugs are evaluated by how they modify the ionic mechanisms underlying electrical activation. Changes in those mechanisms can influence conduction, cellular excitability, or overall rhythm. Examining these three outcomes helps connect a drug’s action on cardiac ion channels with its broader electrophysiological effect and provides a framework for studying whether treatment corrects or disturbs normal cardiac electrical behavior.
An abnormal depolarization pattern can be investigated as more than a contraction problem. Because pharmacology links ionic activation with conduction, excitability, and rhythm, measurements of this electrical event can help characterize arrhythmias and conduction disorders. The same framework also supports evaluation of potential cardiotoxicity, where a drug-related electrical change may signal an unwanted cardiac effect.
Electrocardiography provides a way to examine cardiac electrical activity during the heartbeat at the whole-heart level. In pharmacological studies, ECG measurements can be used to investigate arrhythmias, conduction disorders, and changes associated with drug exposure. This approach connects electrical activation observed in the heart with clinically relevant rhythm and conduction outcomes without requiring interpretation of isolated cells alone.
Cellular electrophysiology examines electrical behavior directly in cardiac cells, allowing investigators to study the ionic mechanisms associated with depolarization. It is especially useful for relating fast sodium-channel activity in atrial and ventricular myocytes to calcium-channel activity in nodal cells. Such measurements help clarify drug effects on cellular excitability and support investigation of potential cardiotoxicity.
The two approaches provide complementary levels of evidence. ECG measurements show how electrical changes relate to cardiac rhythm and conduction, whereas cellular electrophysiology helps examine the underlying ion-channel mechanisms in specific heart-cell types. Together, they support a more complete assessment of antiarrhythmic drug effects, arrhythmias, conduction disorders, and possible cardiotoxicity.