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Curs 11 - Reglarea respiratiei + transport gaze

Terms in this set (102)

Outwardly rectifying K+ channels.
A, Note that in a voltage-clamp experiment, a depolarizing step in Vm activates the current, but with a delay.
B, The current-voltage relationship is shown for a delayed outward rectifying K+ channel, as in A.
C, This A-type K+ current is active at relatively negative values of Vm and tends to hyperpolarize the cell. In a spontaneously spiking neuron, a low level of the A-type current allows Vm to rise relatively quickly toward the threshold, which produces a relatively short interspike interval and thus a high firing rate.
D, In a spontaneously spiking neuron, a high level of the A-type current causes Vm to rise relatively slowly toward the threshold, which produces a relatively long interspike interval and thus a low firing rate.
E, These experiments were performed on four different types of K+ channels (Kv1.1, 1.2, 1.3, and 1.4) from mammalian brain and expressed in Xenopus oocytes. Shown are the results of voltage-clamp experiments in which Vm was stepped from −80 mV to 0 mV. The left panel, at high time resolution, shows that some of these channels activate more slowly than others. The right panel, at a longer time scale, shows that inactivation gradually speeds up from Kv1.1 to Kv1.4.
F, The left panel shows N-type inactivation, so called because the N or amino terminus of the protein is essential for inactivation. Each of the four subunits is thought to have an N-terminal "ball" tethered by a "chain" that can swing into place to block the pore. The right panel shows a variant in which certain β subunits can provide the ball-and-chain for Kv channel α subunits that themselves lack this capability at their N termini.