Which phenomenon explains the unidirectional propagation of action potentials?Select one:Select the correct definitionThe voltage dependence of the sodium channelsThe voltage dependence of the potassium channelsThe presence of a refractory period at a location where an action potential has just passedSufficient "leakiness" of the axons, such that backward propagation of action potentials is preventedThe polarized orientation of microtubules within the axon
Question
Which phenomenon explains the unidirectional propagation of action potentials?Select one:Select the correct definitionThe voltage dependence of the sodium channelsThe voltage dependence of the potassium channelsThe presence of a refractory period at a location where an action potential has just passedSufficient "leakiness" of the axons, such that backward propagation of action potentials is preventedThe polarized orientation of microtubules within the axon
Solution
The phenomenon that explains the unidirectional propagation of action potentials is "The presence of a refractory period at a location where an action potential has just passed".
Here's why:
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An action potential is initiated at one point along the neuron, typically the axon hillock.
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When an action potential occurs, there is a rapid influx of sodium ions into the neuron, which depolarizes the membrane and causes the action potential to propagate down the axon.
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Immediately after the action potential, the neuron enters a refractory period. During this time, it is either impossible (absolute refractory period) or difficult (relative refractory period) for the neuron to initiate another action potential.
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The refractory period thus ensures that the action potential only travels in one direction - from the axon hillock to the axon terminals. This is because the section of the neuron immediately behind the action potential is in its refractory period and cannot be depolarized again so soon.
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Therefore, the presence of a refractory period at a location where an action potential has just passed is the phenomenon that explains the unidirectional propagation of action potentials.
Similar Questions
109. One reason that action potentials are all-or-none is that a. they are always the same size in a given neuron. b. axonal membranes do not allow partial electrical responses to electrical stimuli. c. they must travel long distances without decrement. *d. once the membrane potential is past threshold, the influx of Na+ keeps driving it more positive until the maximum number of Na+ channels is
Complete the sentences describing the events that occur during an action potential.An action potential will not occur unless the membrane potential at the (the initial segment of the axon) reaches a level called .When threshold is reached, of the initial segment open briefly, allowing to diffuse into the cell.As these ions enter the cell, the cell membrane undergoes , with the membrane potential increasing to a peak of approximately +30mV.As the peak of the action potential is reached, the sodium channels close and the open, allowing these ions to diffuse out of the cell.As cations leave the cell, the membrane potential at that part of the membrane once again becomes negative. This phase of the action potential is called , because the resting membrane potential is being reestablished.The membrane potential actually dips lower than -70mV because the potassium channels do not close quickly enough. This phase is called .
Electrical signals that are propagated along axons in a non-decremental fashion are called potentials.
When thinking about an action potential which one of the following statements is TRUE?Question 10Answera.A stimulus changes the permeability of a "patch" of the membrane, and sodium ions (Na+) diffuse rapidly into the cell.b.During repolarization, sodium ions diffuse rapidly into the cell.c.If a stimulus is strong enough, hyperpolarization causes membrane polarity to be completely reversed, and an action potential is initiated.d.Ionic conditions are restored after repolarization by the actions of the sodium-potassium (Na+-K+) pump, whereby two Na+ ions are ejected for every three K+ ions carried back into the cell.e.The external side of the resting membrane is slightly negative, and its internal side is slightly positive.
Describe the events involved in the generation and propagation of an action potential.
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