Ragsdale Lectures: Voltage-Gated Ion Channels

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What is the primary role of voltage-gated potassium channels in an action potential?

Causing the repolarizing phase (correct)

Regulating the resting potential

Maintaining the plateau phase

Initiating the depolarizing phase

What is the state of the voltage-gated potassium channel that is not conducting ions?

Inactivated

Closed (correct)

Activated

Open

What is the approximate difference in permeability of the pore to K+ versus Na+?

1,000 times

100 times

100,000 times

10,000 times (correct)

What is the purpose of the signature sequences of the four pore loops in the selectivity filter?

To form a narrow opening at the outer end of the pore Signup and view all the answers

What is the primary interaction between K+ ions and the pore carbonyl oxygens?

Electrostatic Signup and view all the answers

Why does the energy required for dehydration of K+ ions not apply to Na+ ions?

The energy required for dehydration is not gained back by interactions in the pore for Na+ Signup and view all the answers

How many K+ ions occupy the selectivity filter at physiological ionic concentrations?

Two Signup and view all the answers

What facilitates rapid ion flux through the pore?

Electrostatic repulsions between K+ ions Signup and view all the answers

What is the primary function of backpropagation of action potentials in the dendrites of brain neurons?

To enable synapses to get information about the output activity of the neuron Signup and view all the answers

What is the role of Mg2+ ions in NMDA receptors at excitatory synapses?

To block NMDA receptors at the resting membrane potential Signup and view all the answers

What is the phenomenon where the strength of a synapse depends on the timing of glutamate release and postsynaptic action potential?

Spike timing dependent plasticity Signup and view all the answers

What is the characteristic of thalamic neurons that enables them to switch between transmission and bursting modes?

Their resting membrane potential Signup and view all the answers

What is the type of calcium channel that is responsible for the bursting mode in thalamic neurons?

T-type calcium channel Signup and view all the answers

What is the characteristic of T-type calcium channels that enables them to contribute to the bursting mode?

Their ability to activate at negative membrane potentials Signup and view all the answers

What is the role of HCN (Ih) channels in thalamic bursting?

To enable the bursting mode Signup and view all the answers

What is the typical duration of the quiet periods between bursts of action potentials in thalamic neurons?

100s of milliseconds Signup and view all the answers

What is the effect of electrostatic repulsion between K+ ions within the selectivity filter on ion flux?

It reduces the energy barrier for exiting the pore Signup and view all the answers

What determines the calcium channel selectivity?

A ring of glutamate residues in the pore loops Signup and view all the answers

What is the effect of deleting the N-terminus of the potassium channel on inactivation?

It eliminates inactivation Signup and view all the answers

What is the disorder caused by Nav1.1 mutations?

Severe myoclonic epilepsy of infancy (SMEI) Signup and view all the answers

What is the effect of voltage-clamp on ion channels?

It controls the membrane potential and directly measures the current flowing through ion channels Signup and view all the answers

What is the effect of SCN1A knockouts on inhibitory interneurons?

They are less able to sustain trains of action potentials Signup and view all the answers

What is the type of current that is activated at subthreshold voltages and helps drive the membrane to the action potential threshold?

TTX-sensitive Nav1.7 current Signup and view all the answers

What is the distribution of voltage-gated ion channels in brain neurons?

Covered on neuronal cell bodies and dendrites Signup and view all the answers

Which of the following NMDA receptor subunits are extrasynaptic?

GluN2B Signup and view all the answers

What is required for the activation of NMDA receptors?

Binding of glutamate and glycine to separate sites Signup and view all the answers

What is the function of the magnesium ion in NMDA receptors?

To block the pore at resting membrane potentials Signup and view all the answers

What is the structure of the ligand-binding domain (LBD) in GluR subunits?

A clamshell-like structure formed by D1 and D2 Signup and view all the answers

What is the effect of agonist binding on the GluR subunit?

It pulls the D2 domain upward, closing the clamshell Signup and view all the answers

Which of the following receptors are part of the Cys-loop ion channel family?

Nicotinic acetylcholine receptors Signup and view all the answers

What is the function of the TM2 segments in nicotinic acetylcholine receptors?

They line the pore Signup and view all the answers

What is the effect of ACh binding on the nicotinic acetylcholine receptor?

It causes the kinks to pivot, opening the pore Signup and view all the answers

What is the effect of membrane hyperpolarization on HCN channels?

It activates the channel Signup and view all the answers

What is the frequency of the intrinsic rhythm of the oscillations in thalamic neurons?

0.5-4 Hz Signup and view all the answers

What is the role of neuromodulators such as acetylcholine in thalamic and reticular thalamic neurons?

They depolarize the neurons Signup and view all the answers

What is the mechanism of bursting in reticular thalamic neurons?

It involves a K+ channel that is activated by intracellular Ca2+ Signup and view all the answers

What is the function of working memory in the brain?

It provides an interface between perception, long-term memory and action Signup and view all the answers

What is the effect of the editing of mRNA encoding GluA2 by RNA-specific adenosine deaminase?

It changes the channel from Ca permeable to Ca impermeable Signup and view all the answers

What is the role of AMPA receptors in the brain?

They are involved in excitatory synapses Signup and view all the answers

What is the requirement for functional NMDA receptors?

GluN1 is required Signup and view all the answers