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When threshold is reached depolarization occurs with the same amplitude of potential change This is known as?
Wiki User
∙ 11y ago
the all or none law
Wiki User
∙ 11y ago
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What ion is rapidly moving into the cell during the depolarization period of an action potential?
Sodium.A positive ion (cation) that enters the cell (influx) rapidly when the membrane threshold is reached and the voltage gated sodium channels open.This occurs during the rising phase of an action potential, i.e. membrane depolarization beyond the threshold for activation.
Why don't the terms depolarization and action potential mean the same thing?
Depolarization occurs when a stimulus opens sodium channels which allow more sodium to go into the membrane making it less negative and more positive (toward reaching threshold). An action potential can only occur once the membrane reaches threshold which means it has reached the level needed through depolarization. An action potential is a brief reversal in polarity of the membrane making the inside more positive and the outside more negative, the reverse occurs again once the membrane reaches resting potential.
What effect of the action potential if sodium channels are kept closed?
The action potential will not generate if the sodium channels are kept closed.This is because the sodium channels are responsible for the dramatic rising phase of membrane depolarization that occurs when the threshold of activation is reached. As a membrane potential gradually depolarizes (which can occur for a variety of reasons such as neurotransmitter stimulation, mechanical deformation of the membrane, etc), that membrane potential gradually comes closer to that threshold of activation. Once that threshold is reached, the voltage gated sodium channels open and allow for a dramatic influx of sodium ions into the cell. This results in a rapid depolarization which is seen as the rising phase of that upward spike noted in an action potential. Without the ability to open these sodium channels we may reach the threshold of activation, but the actual action potential will not occur.
How does a nerve impulse follow the all or nothing principle?
The action action potential produced needs to reach the threshold for the AP to be propagated. If it doesn't reach the threshold, there is not enough Na+ to stimulate the positive feedback system which allows the action potential to be self-propagated. Instead, K+ channels will be opened, and it will enter repolarisation phase, and the AP wll not be conducted.
When the ions are moving across the membrane during the depolarization and repolarization phases of an action potential they are moving by?
Depends on what stage you are talking about. Stimulus of sodium ions from dendrites of other neurons must reach a threshold. Once that threshold is reached, sodium ions quickly diffuse into the neuron via facilitative diffusion, depolarizing the neuron. Upon this occurring, sodium channels close and potassium ions are pumped out of the neuron via active transport, leading to repolarization of the neuron.
What ion is rapidly moving into the cell during the depolarization period of an action potential?
Sodium.A positive ion (cation) that enters the cell (influx) rapidly when the membrane threshold is reached and the voltage gated sodium channels open.This occurs during the rising phase of an action potential, i.e. membrane depolarization beyond the threshold for activation.
Why don't the terms depolarization and action potential mean the same thing?
Depolarization occurs when a stimulus opens sodium channels which allow more sodium to go into the membrane making it less negative and more positive (toward reaching threshold). An action potential can only occur once the membrane reaches threshold which means it has reached the level needed through depolarization. An action potential is a brief reversal in polarity of the membrane making the inside more positive and the outside more negative, the reverse occurs again once the membrane reaches resting potential.
When threshold is reached at the SA node what channels open causing further depolarization of the membrane?
Fast Calcium
What effect of the action potential if sodium channels are kept closed?
The action potential will not generate if the sodium channels are kept closed.This is because the sodium channels are responsible for the dramatic rising phase of membrane depolarization that occurs when the threshold of activation is reached. As a membrane potential gradually depolarizes (which can occur for a variety of reasons such as neurotransmitter stimulation, mechanical deformation of the membrane, etc), that membrane potential gradually comes closer to that threshold of activation. Once that threshold is reached, the voltage gated sodium channels open and allow for a dramatic influx of sodium ions into the cell. This results in a rapid depolarization which is seen as the rising phase of that upward spike noted in an action potential. Without the ability to open these sodium channels we may reach the threshold of activation, but the actual action potential will not occur.
How does a nerve impulse follow the all or nothing principle?
The action action potential produced needs to reach the threshold for the AP to be propagated. If it doesn't reach the threshold, there is not enough Na+ to stimulate the positive feedback system which allows the action potential to be self-propagated. Instead, K+ channels will be opened, and it will enter repolarisation phase, and the AP wll not be conducted.
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.
When the ions are moving across the membrane during the depolarization and repolarization phases of an action potential they are moving by?
Depends on what stage you are talking about. Stimulus of sodium ions from dendrites of other neurons must reach a threshold. Once that threshold is reached, sodium ions quickly diffuse into the neuron via facilitative diffusion, depolarizing the neuron. Upon this occurring, sodium channels close and potassium ions are pumped out of the neuron via active transport, leading to repolarization of the neuron.
An action potential either fires completely or not at all. this is know as?
"all-or-none principle." In this principle, once the threshold for firing an action potential is reached, it will occur at full strength regardless of the strength of the stimulus that triggered it.
What happens to the net concentration of sodium ions during the resting membrane potential?
Once the threshold has been reached the fast sodium channels open and sodium ions rush into the cell.
What causes rapid depolarization phase of a pacemaker cell?
Rapid depolarization happens after the membrane threshold has been reached and Na+ ions start to flow into the cell. As more Na+ ions flood in the cell becomes more and more positive. This causes the voltage gated Na+ channels to open creating a flood of Na+ ions and thus a rapid phase of depolarization. Shortly after this rapid phase K+ ions are released from the cell causing the cell to become more negative closing the Na+ channels and thus repolarizing the cell.
What is the maximum height reached by a wave from its rest position?
amplitude
When the out of pocket threshold is reached benefits are payable at what percentage?
Out-of-Pocket Threshold @100% of eligible expenses during a calendar year
