What is endothelium dependent hyperpolarization?
Endothelium-dependent hyperpolarizing factor (EDHF) is a powerful vasodilator influence in small resistance arteries and thus an important modulator of blood pressure and flow. As the name suggests, EDHF was thought to describe a diffusible factor stimulating smooth muscle hyperpolarization (and thus vasodilatation).
Why does hyperpolarization cause vasodilation?
The hyperpolarization may contribute to the mechanism of dilation by causing voltage-dependent calcium channels to close. Recent evidence indicates that the response to hyperpolarizing vasodilators is mediated through activation of ATP-sensitive potassium (Katp) channels.
How does hyperpolarization lead to relaxation?
Stimulation of the endothelial lining of arteries with acetylcholine results in the release of a diffusible substance that relaxes and hyperpolarizes the underlying smooth muscle. Nitric oxide (NO) has been a candidate for this substance, termed endothelium-derived relaxing factor.
What are the mechanisms which account for EDh?
This mechanism is due to the action of a so-called endothelium-derived hyperpolarizing factor (EDHF) and is dependent on either the release of diffusible factor(s) and/or to a direct contact-mediated mechanism. 2. Most evidence supports the concept that ‘EDHF’ activity is dependent on contact-mediated mechanisms.
What happens to muscle during hyperpolarization?
Hyperpolarization up to -45 mV by injection of constant current caused relaxation. Depolarization caused contraction. Pulses of field stimulation caused a brief depolarization which was reduced by tetrodotoxin or by stripping of the adventitia.
How does EDH relax arteries?
In some arteries, K+ released from endothelial KCa channels activates endothelial Kir channels, which in turn amplifies EDH. EDH spreads to adjacent smooth muscle cells via myoendothelial gap junctions (MEGJs), resulting in vascular relaxation.
What is hyperpolarization and depolarization?
Hyperpolarization is when the membrane potential becomes more negative at a particular spot on the neuron’s membrane, while depolarization is when the membrane potential becomes less negative (more positive). The opening of channels that let positive ions flow into the cell can cause depolarization.
What change in membrane potential depolarization or hyperpolarization triggers an action potential?
2. What change in membrane potential (depolarization or hyperpolarization) triggers an action potential? A depolarization in the membrane potential results in an action potential. The membrane potential must become less negative to generate an action potential.
What is the difference between a hyperpolarization and a depolarization?