![]() It's just confusing that when talking about action potentials, we're taught that sodium and potassium are flowing both ways and I want to clarify when they flow in/out and why. This is the opposite of what I had just described in an action potential, which is confusing me.Ĭan you clarify the difference for me please? So I'm assuming that the diffusion of Na+ influx and K+ out of the cell is during an action potential, and the Na+/K+ ATPase function (in pumping these ions in the OPPOSITE direction) is to return to resting membrane potential AFTER the action potential? ![]() So this means that K+ flows in and Na+ flows out. Now this is active transport, requiring ATP, therefore pumping these ions against their gradients. Ok, so then there's also the Na+/K+ ATPase. I'm hoping you can clarify something for me? I understand that there's more Na+ outside the cell and more K+ inside the cell this relates to how Na+ initially flows into the cell (depolarization) and K+ flows out of the cell (repolarization) during an action potential, correct? (And this is done via diffusion across the membrane, right?) The presence of Ca-activated (SK) potassium channels in the spine head provides a negative-feedback loop regulating synaptic depolarization. Relative refractory periods can help us figure how intense a stimulus is - cells in your retina will send signals faster in bright light than in dim light, because the trigger is stronger. This means that the initial triggering event would have to be bigger than normal in order to send more action potentials along. Voltage-sensitive calcium channels (VSCCs) and NMDA receptors provide a major mode of calcium entry in neurons and trigger downstream signaling cascades that control dendrite de- velopment (Konur and Ghosh 2005 Cline and Haas 2008). It would take even more positive ions than usual to reach the appropriate depolarization potential than usual. However, the cell is still hyperpolarized after sending an action potential. This is the period after the absolute refractory period, when the h gates are open again. Relative refractory period: during this time, it is really hard to send an action potential. Here, in awake mice, authors combine simultaneous dendritic recording of voltage and calcium signals, with somatic recording from Purkinje neurons, enabling characterization of dendritic spiking.Absolute refractory periods help direct the action potential down the axon, because only channels further downstream can open and let in depolarizing ions. No sodium means no depolarization, which means no action potential. The inactivation (h) gates of the sodium channels lock shut for a time, and make it so no sodium will pass through. Absolute refractory period: during this time it is absolutely impossible to send another action potential.
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