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What channels are open during depolarization and during repolarization?
Wiki User
∙ 13y ago
During depolarization Na channels are open
During repolarization K channels are open
Wiki User
∙ 13y ago
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What changes occur in the neuron?
Neurons undergo depolarization and repolarization when stimulated. The sodium and potassium channels open.
Why do not action potentials occur during the repolarization phase?
It has to do with what types of channels are open during this phase. In the repolarization phase the number of potassium channels are increased and the number of sodium channels are decreased. This allows for action potentials to not occur. Otherwise, the action potentials would add up and produce tetany.
Potassium channels open late in the action potential to cause membrane?
...repolarization
When threshold is reached at the SA node what channels open causing further depolarization of the membrane?
Fast Calcium
What ion flows into a nerve cell when an axon's membrane depolarizes?
During the depolarization phase, sodium ions enter the cell through the open ion-channels (Na+ influx).
What causes calcium channels in the synaptic knob to open?
depolarization of the presynaptic membrane due to an arriving action potential
What helps maintain the resting potential of a neuron?
During resting potential, the Sodium-Potassium pump is inactive. Therefore, it is indirectly responsible for the resting potential. However, Potassium diffuses outside the membrane via "leakage" channels, and causes the resting potential.
What changes occur to voltage-gated Na and K channels at the peak of depolarization?
Inactivation gates of voltage-gated Na+ channels close, while activation gates of voltage-gated K+ channels open.
Why can't an action potential be generated during the absolute refractory period?
Action potentials cannot be generated during the absolute refractory period, as not enough ion channels are able to respond to the stimulus, no matter how large it is. Using Na+ fast channels as an example, during depolarization the "gate" of the channel is opened, allowing for Na+ influx into the cell. However, during the repolarization phase, a second "gate" marks the closure of the cell, preventing any further movement of ions into the cell. However, this also means that the channel is unable to open again until the second gate is removed, and the first gate returns back into place.
What are the Stages of nerve impulses?
The action potential has 5 main phases:1) stimulation/rising phase - depolarization caused by influx of sodium ions at the axon hillock; potential increases from a resting potential of -70 mV2) peak phase - depolarization and membrane potential reaches a peak, with sodium channels open maximally, at about +40 mV3) falling phase - potassium channels open in response, causing a subsequent reduction in membrane potential, and the neuron begins to repolarize4) hyperpolarization/undershoot phase - more potassium channels stay open after sodium channels close, causing a hyperpolarization of the neuronal membrane, bringing the potential down below its initial resting potential (below -70 mV)5) refractory phase - potassium channels begin to close, allowing the membrane potential to revert back to the resting potential of -70 mV; during this phase, the probability of the nerve being able to refire is extremely low, thus allowing for a delay between action potentials
Which is the first step in a neuron production of an action potential?
Depolarization is the first event in action potential. During depolarization, the sodium gates open and the membrane depolarizes.
How are nerve impulses prevented from traveling the wrong way on axon?
On the axon hillock, there is a concentration of sodium channels whose role are to initiate the depolarization and signal transmission allong the axon. Once the all or none threshold is reached, depolarization occurs in a cascade unidirectional along the length of the axon, with potassium channels open just following the sodium-channel mediated depolarization, such that there is no back-propagation of the signal.
