How do sodium channels affect the heart?
Voltage-gated sodium (Na) channels are transmembrane proteins responsible for the rapid upstroke of the cardiac action potential, and for rapid impulse conduction through cardiac tissue. As such, Na channel function is central to the genesis of cardiac arrhythmias and their complex pharmacology.
Are there sodium channels in the heart?
Sodium channels are the arch-type of voltage-gated ion channels. The human cardiac sodium channel hNaV1.5 is a member of the family of voltage-gated sodium channels (hNaV1 to 9). The channel consists of a primary α- and multiple secondary β-subunits.
What is the role of sodium in the cardiac action potential?
Opening of the primary cardiac voltage-gated sodium (Nav1.5) channel initiates cellular depolarization and the propagation of an electrical action potential that promotes coordinated contraction of the heart.
What is cardiac resting potential?
A healthy myocardial cell has a resting membrane potential of approximately ~90 mV (Figure 3). This resting potential can be described by the Goldman-Hodgkin-Katz equation, which takes into account the permeability (P) as well as the intracellular and extracellular concentration of ions [X], where X is the ion.
What drugs block sodium channels?
Local anesthetics, antiarrhythmics, and anticonvulsants include both charged and electroneutral compounds that block voltage-gated sodium channels.
What causes depolarization of the heart?
Because of slow inward current of sodium and a voltage gated increase in calcium conductance (via T channels) Phase 0—depolarization. As opposed to the ventricular muscle action potential, this occurs because of voltage gated calcium channels opening.
What happens to the sodium channel in Brugada syndrome?
Approximately 15%-30% of individuals with Brugada syndrome have a SCN5A gene mutation. This gene is responsible for the production of a protein that allows movement of sodium atoms into heart muscle cells through a channel called the sodium channel.
What happens to sodium channels during depolarization?
The steepness of the voltage dependence of opening or activation varies between channels. Sodium channels increase their activation by ≈e-fold (2.73) for 4 mV of depolarization; in contrast, the K + channel activation increase e-fold for 5 mV of depolarization. 4
Which is the least studied ion channel in the heart?
The mechanosensitive or stretch-activated channels are the least studied. They belong to a class of ion channels that can transduce a physical input such as stretch into an electric signal through a change in channel conductance. Acute cardiac dilatation is a well-recognized cause of cardiac arrhythmias.
What is the action potential of the cardiac ion channel?
Phase 0 is the phase of rapid depolarization. The membrane potential shifts into positive voltage range. This phase is central to rapid propagation of the cardiac impulse (conduction velocity, θ=1 m/s). Phase 1 is a phase of rapid repolarization. This phase sets the potential for the next phase of the action potential.