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An electrical state in an excitable cell whereby the inside of the cell is made less negative relative to the outside than at the resting membrane potential.
Certain external stimuli reduce the charge across the plasma membrane.
Change in the potential that normally exists across the plasma membrane of a cell at rest, resulting in a less negative membrane potential.
~ of the T-tubule membrane causes a release of calcium ions from the sarcoplasmic reticulum, triggering muscle contraction.
~ The loss of an electrical charge on the surface of a membrane.
depolarized The reduction in the difference in charge (potential) between the outside and inside of a membrane.
deposit feeder An animal that feeds on organic matter that settles on the bottom. Compare suspension feeder.
~ - a shift in the membrane potential to a less negative value; triggered by an action potential
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In most neurons, depolarizations are graded only up to a certain membrane voltage, called the threshold.
A stimulus strong enough to produce a depolarization that reaches the threshold triggers a different type of response, called an action potential.
43. How is the depolarization of the neuronal plasma membrane generated? How does the cell return to its original rest?
For example, depolarization of cultured neurons triggers the skipping of exon 18 of the neural cell adhesion gene, a change accompanied by H3K9 hyper-acetylation around the exon . The effect of depolarization can be further potentiated by treating the cells with a histone deacetylase inhibitor.
The ~ of the pre-synaptic membrane results in the opening of voltage gated calcium channels.
The ~ travels in one direction down the axon of the neuron to the opposite end of the cell. At the "far" end, the neuron has small vesicles containing a neurotransmitter which is released when the membrane ~ occurs there.
The resulting activation of voltage-gated Na+ channels boosts the graded depolarization produced by TRPM5 to the high voltage threshold required for gating the gap-junction hemi-channels. Romanov et al.
This change in the membrane potential, called depolarization, will cause the voltage-gated sodium channels to open. Sodium ions will rush in, resulting in a rapid change in the charge. At the peak of the action potential, that area of the neuron is about 40 mV positive.
An increase in the threshold for an action potential that occurs in some neurons during a slowly developing or prolonged depolarization. The result is that only a few action potentials are generated during prolonged depolarization above the normal threshold level.
The beat is actually much more complex and involves other ions. But the end result of this depolarization-repolarization is that the contractile filaments in the cell engage, and the cell contracts.
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There is an area, however, which does conduct in the septum, and the waves can pass from here through the ventricles. This specialised area is called the atrioventricular node (AVN) and will pass on the waves of depolarization after about 0.1s.
See also: What is the meaning of Action, Membrane, Cell, Trans, Cells?