40 Questions
What is the primary role of voltage-gated potassium channels in an action potential?
Causing the repolarizing phase
What is the state of the voltage-gated potassium channel that is not conducting ions?
Closed
What is the approximate difference in permeability of the pore to K+ versus Na+?
10,000 times
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
What is the primary interaction between K+ ions and the pore carbonyl oxygens?
Electrostatic
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+
How many K+ ions occupy the selectivity filter at physiological ionic concentrations?
Two
What facilitates rapid ion flux through the pore?
Electrostatic repulsions between K+ ions
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
What is the role of Mg2+ ions in NMDA receptors at excitatory synapses?
To block NMDA receptors at the resting membrane potential
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
What is the characteristic of thalamic neurons that enables them to switch between transmission and bursting modes?
Their resting membrane potential
What is the type of calcium channel that is responsible for the bursting mode in thalamic neurons?
T-type calcium channel
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
What is the role of HCN (Ih) channels in thalamic bursting?
To enable the bursting mode
What is the typical duration of the quiet periods between bursts of action potentials in thalamic neurons?
100s of milliseconds
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
What determines the calcium channel selectivity?
A ring of glutamate residues in the pore loops
What is the effect of deleting the N-terminus of the potassium channel on inactivation?
It eliminates inactivation
What is the disorder caused by Nav1.1 mutations?
Severe myoclonic epilepsy of infancy (SMEI)
What is the effect of voltage-clamp on ion channels?
It controls the membrane potential and directly measures the current flowing through ion channels
What is the effect of SCN1A knockouts on inhibitory interneurons?
They are less able to sustain trains of action potentials
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
What is the distribution of voltage-gated ion channels in brain neurons?
Covered on neuronal cell bodies and dendrites
Which of the following NMDA receptor subunits are extrasynaptic?
GluN2B
What is required for the activation of NMDA receptors?
Binding of glutamate and glycine to separate sites
What is the function of the magnesium ion in NMDA receptors?
To block the pore at resting membrane potentials
What is the structure of the ligand-binding domain (LBD) in GluR subunits?
A clamshell-like structure formed by D1 and D2
What is the effect of agonist binding on the GluR subunit?
It pulls the D2 domain upward, closing the clamshell
Which of the following receptors are part of the Cys-loop ion channel family?
Nicotinic acetylcholine receptors
What is the function of the TM2 segments in nicotinic acetylcholine receptors?
They line the pore
What is the effect of ACh binding on the nicotinic acetylcholine receptor?
It causes the kinks to pivot, opening the pore
What is the effect of membrane hyperpolarization on HCN channels?
It activates the channel
What is the frequency of the intrinsic rhythm of the oscillations in thalamic neurons?
0.5-4 Hz
What is the role of neuromodulators such as acetylcholine in thalamic and reticular thalamic neurons?
They depolarize the neurons
What is the mechanism of bursting in reticular thalamic neurons?
It involves a K+ channel that is activated by intracellular Ca2+
What is the function of working memory in the brain?
It provides an interface between perception, long-term memory and action
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
What is the role of AMPA receptors in the brain?
They are involved in excitatory synapses
What is the requirement for functional NMDA receptors?
GluN1 is required
Learn about the voltage-gated ion channel superfamily, specifically voltage-gated potassium channels and their role in the action potential. Understand how they function and the selectivity filter that allows K+ ions to pass through.
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