What is delayed rectifier current?
Delayed rectifier channels conduct outward currents during the plateau phase of cardiac action potentials and play critical roles in the timing of cardiac repolarization.
What do inward rectifiers do?
Inward rectifiers play a role in setting cellular membrane potentials, and closing of these channels upon depolarization permits the occurrence of long duration action potentials with a plateau phase. Inward rectifiers lack the intrinsic voltage sensing helices found in many VIC family channels.
How does the conductance of an inward rectifying ion channel change with membrane depolarization?
Canonical inward rectifiers in their native tissues exhibit “strong” inward rectification, with little outward current during depolarization. This is because their conductance declines steeply with membrane depolarization or with increasing deviation of the membrane potential from EK (V − EK; Hille, 2001).
How do inward rectifying potassium channels cause hyperpolarization?
The phenomenon of inward rectification of IK1 channels results from high-affinity and strongly voltage-dependent blockade of the inner channel pore by cytosolic magnesium (Mg2+), Ca2+, and polyamines (spermine, spermidine, putrescine), which plug the channel pore at depolarized potentials, resulting in a decline in …
What is a-Type current?
A-type currents are voltage-gated, calcium-independent potassium (Kv) currents that undergo rapid activation and inactivation. Commonly associated with neuronal and cardiac cell-types, A-type currents have also been identified and characterized in vascular, genitourinary, and gastrointestinal smooth muscle cells.
What are a-type potassium channels?
A-type voltage-gated potassium (Kv) channels are major regulators of neuronal excitability that have been mainly characterized in the central nervous system.
Are Kir channels voltage gated?
In contrast to voltage gated potassium channels, which require membrane depolarization to open, strongly rectifying Kir channels remain active around the physiological resting membrane potential, and sharply diminish their activity upon membrane depolarization (Nichols and Lopatin, 1997; Lu, 2004; Hibino et al., 2010).
What does outwardly rectifying mean?
current current
outwardly rectifying current current that rectifies so that it passes more easily towards the exterior of a cell.
Are Kir channels voltage-gated?
What is meant by inward rectifier in the context of inward rectifier potassium channel?
Inward rectifiers are a class of K+ channels that can conduct much larger inward currents at membrane voltages negative to the K+ equilibrium potential than outward currents at voltages positive to it, even when K+ concentrations on both sides of the membrane are made equal.
What are a type potassium channels?
What is a delayed rectifier potassium channel?
The delayed rectifier potassium channels are a family of potassium channels that allow a sustained K+ efflux with a delay after membrane depolarization. The outflow of potassium ions rapidly repolarizes the membrane.
What do leak channels and inward rectifier channels do?
They, along with the “leak” channels, establish the resting membrane potential of the cell.
How are delayed rectifier and a type potassium channels different?
These channels differ from the potassium channels that are typically responsible for repolarizing a cell following an action potential, such as the delayed rectifier and A-type potassium channels.
Which is inward rectifier potassium channel ( Irk )?
Inward-rectifier potassium channels ( Kir, IRK) are a specific lipid-gated subset of potassium channels. To date, seven subfamilies have been identified in various mammalian cell types, plants, and bacteria. They are activated by phosphatidylinositol 4,5-bisphosphate ( PIP 2 ).
How are inward rectifiers different from tandem pore domain potassium channels?
Inward rectifiers also differ from tandem pore domain potassium channels, which are largely responsible for “leak” K + currents.
