Related Concept Videos
01:28Action Potential: Phases of Stimulation
The action potential is a complex electrical event that occurs in excitable cells, such as neurons and muscle cells. It consists of several distinct phases, each with specific characteristics.
Resting Phase:
In this phase, the cell's membrane is at its resting potential, typically around -70 millivolts (mV) for neurons. Inside the cell, there is a higher concentration of potassium ions (K+) and a lower concentration of sodium ions (Na+). Voltage-gated sodium channels are closed, and...
Resting Phase:
In this phase, the cell's membrane is at its resting potential, typically around -70 millivolts (mV) for neurons. Inside the cell, there is a higher concentration of potassium ions (K+) and a lower concentration of sodium ions (Na+). Voltage-gated sodium channels are closed, and...
01:23Propagation of Action Potentials
The propagation of an action potential refers to the process by which a nerve impulse, or "action potential," travels along a neuron.
Neurons (nerve cells) have a resting membrane potential, with a slightly negative charge inside compared to outside. This is maintained by ion channels, such as sodium (Na+) and potassium (K+) channels, which control the flow of ions. When a stimulus, like a touch or a signal from another neuron, triggers the neuron, sodium channels open, allowing sodium ions to...
Neurons (nerve cells) have a resting membrane potential, with a slightly negative charge inside compared to outside. This is maintained by ion channels, such as sodium (Na+) and potassium (K+) channels, which control the flow of ions. When a stimulus, like a touch or a signal from another neuron, triggers the neuron, sodium channels open, allowing sodium ions to...
01:30Cardiac Action Potential
Cardiac action potentials are essential for proper heart function, enabling the rhythmic contractions needed for adequate blood circulation. Nodal cells and Purkinje fibers, specialized for electrical conduction, generate these action potentials.
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
01:19Electrophysiology of Normal Cardiac Rhythm
The normal cardiac rhythm is a synchronized electrical activity that facilitates the regular and coordinated contraction of the heart muscle. This process is essential for efficient blood circulation throughout the body. The fundamental elements involved in establishing and maintaining this rhythm include the unique electrical properties of cardiac muscle cells, the sinoatrial (SA) node's pacemaker function, the specialized conducting system, and the ionic mechanisms underlying each phase of...
01:28Mechanism of Cardiac Arrhythmias
Arrhythmias are irregular heart rhythms occurring when the heart's electrical impulses become abnormal. These disturbances can lead to various symptoms, depending on their severity and the underlying cause. Some common factors contributing to arrhythmias include hypoxia, ischemia, electrolyte imbalances, excessive catecholamine exposure, drug toxicity, and muscle overstretching. Arrhythmias can be classified into two main types based on the rate and site of origin of abnormal heart rhythms.
01:19The Role of Ion Channels in Neuronal Computation
A postsynaptic neuron usually receives numerous impulses from several other presynaptic neurons. The axon hillock of the postsynaptic neuron integrates all these signals and determines the likelihood of firing an action potential.
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential.
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential.
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Updated: Jun 22, 2026
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Recapitulation of an Ion Channel IV Curve Using Frequency Components
Published on: February 8, 2011
Instability in action potential morphology underlies phase 2 reentry: a mathematical modeling study.
Anat Maoz1, Trine Krogh-Madsen, David J Christini
1Greenberg Division of Cardiology, Weill Cornell Medical College, New York, New York 10065, USA.
Heart Rhythm
|May 27, 2009
Summary
Phase 2 reentry, a cause of abnormal heart rhythms, is driven by unstable action potential (AP) switching, not just differing AP shapes. This finding impacts understanding cardiac electrophysiology and arrhythmia development.
Area of Science:
- Cardiac electrophysiology
- Computational biology
- Biophysics
Background:
- Phase 2 reentry involves electrotonic current propagation between normal and abbreviated action potential (AP) sites, leading to reexcitation.
- The presence of distinct AP morphologies in adjacent regions was thought to be sufficient for phase 2 reentry development.
Purpose of the Study:
- Investigate the mechanism of phase 2 reentry in simulated cardiac tissues.
- Examine the role of gradients in ionic currents, specifically the transient outward current conductance G(to), in phase 2 reentry.
Main Methods:
- Utilized single-cell simulations with the Luo-Rudy dynamic model to assess varying G(to) values.
- Employed one-dimensional fiber simulations to study the spatiotemporal dynamics of phase 2 reentry.
Main Results:
- High G(to) values resulted in abbreviated APs with loss-of-dome morphology, while low/normal values produced notch-and-dome APs.
- Intermediate G(to) values induced intermittent switching between AP morphologies.
- Phase 2 reentry occurred in simulations when cells exhibited unstable switching behavior near critical G(to) ranges.
Conclusions:
- The primary driver of phase 2 reentry is unstable AP morphology switching within a cell population, rather than stable differences between adjacent regions.
- Understanding AP instability is crucial for comprehending phase 2 reentry mechanisms.