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NA plus channels open in response to a change in the membrane potential, causing the channel to undergo conformational changes that lead to its opening. This change in membrane potential can be initiated by various stimuli, such as neurotransmitter binding or depolarization of the cell.
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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 membrane regions would have a significant number of voltage-gated ions K plus and Na plus ion channels?
axon and schwann cell
What opens first in response to threshold stimulus?
The activation gates of voltage-gated Na+ channels open, and Na+ diffuses into the cytoplasm.
Do the action potential travel along the axon of a neuron?
fig. 1Formation of an action potentialThe formation of an action potential can be divided into five steps. (1) A stimulus from a sensory cell or another neuron causes the target cell to depolarize toward the threshold potential. (2) If the threshold of excitation is reached, all Na+ channels open and the membrane depolarizes. (3) At the peak action potential, K+ channels open and K+ begins to leave the cell. At the same time, Na+ channels close. (4) The membrane becomes hyperpolarized as K+ ions continue to leave the cell. The hyperpolarized membrane is in a refractory period and cannot fire. (5) The K+ channels close and the Na+/K+ transporter restores the resting potential.
Influx of Na plus till 70mV?
The electrical potential difference across a cell membrane (the resting potential) is around -65 mV, inside negative. In nerve cells (neurones) or muscle cells this potential difference is reversed during an action potential. Sodium (Na+) channels open and Na+ ions enter the cell down their concentration gradient. This entry of positive charge depolarises the membrane ie it cancels out the resting pootential and then reverses it, so the potential becomes positive inside and negative outside, giving a potential of about +50mV.
What channels are open during depolarization and during repolarization?
During depolarization Na channels are open During repolarization K channels are open
When do voltage-gated Na channels open during an action potential?
Voltage-gated Na channels open at the beginning of an action potential when the membrane potential reaches a certain threshold level.
When do voltage-gated Na channels open during neuronal signaling?
Voltage-gated Na channels open during neuronal signaling when the membrane potential reaches a certain threshold level.
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 is the membrane potential for 3 K plus and 0 Na plus channels the same as that for 5 K plus and 0 Na plus channels?
The membrane potential is determined by the distribution of ions across the membrane and their relative permeabilities. In both cases, if there are only potassium (K⁺) channels and no sodium (Na⁺) channels, the membrane potential will primarily reflect the equilibrium potential for potassium, which is governed by the Nernst equation. Thus, whether there are 3 K⁺ channels or 5 K⁺ channels, the increased conductance from more K⁺ channels does not change the equilibrium potential for potassium, leading to the same membrane potential in both scenarios.
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 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 membrane regions would have a significant number of voltage-gated ions K plus and Na plus ion channels?
axon and schwann cell
What opens first in response to a threshold stimulus?
The activation gates of voltage-gated Na+ channels open, and Na+ diffuses into the cytoplasm.
What opens first in response to threshold stimulus?
The activation gates of voltage-gated Na+ channels open, and Na+ diffuses into the cytoplasm.
Do the action potential travel along the axon of a neuron?
fig. 1Formation of an action potentialThe formation of an action potential can be divided into five steps. (1) A stimulus from a sensory cell or another neuron causes the target cell to depolarize toward the threshold potential. (2) If the threshold of excitation is reached, all Na+ channels open and the membrane depolarizes. (3) At the peak action potential, K+ channels open and K+ begins to leave the cell. At the same time, Na+ channels close. (4) The membrane becomes hyperpolarized as K+ ions continue to leave the cell. The hyperpolarized membrane is in a refractory period and cannot fire. (5) The K+ channels close and the Na+/K+ transporter restores the resting potential.
Influx of Na plus till 70mV?
The electrical potential difference across a cell membrane (the resting potential) is around -65 mV, inside negative. In nerve cells (neurones) or muscle cells this potential difference is reversed during an action potential. Sodium (Na+) channels open and Na+ ions enter the cell down their concentration gradient. This entry of positive charge depolarises the membrane ie it cancels out the resting pootential and then reverses it, so the potential becomes positive inside and negative outside, giving a potential of about +50mV.
