Ion selectivity and gating properties are major parameters used to what?

Characterize ion channel functions

Patch clamp recording, cloning and genetic engineering and x-ray crystallography are all methods used to what?

Investigate ion channel structure and function

What are the two methods by which ion channel gating is affected?

Physical (voltage changes or stretch changes) or chemical (intra or extracellular ligands)

What are ligand-gated ion channels called?

Ionotropic receptors

What are G-protein coupled receptors called?

Metabotrophic receptors

Neurotransmitter receptors and calcium-activated potassium channels are both what?

Ionotropic

Cyclic nucleotide gated channels are all what kind of receptor?

GPCR (metabotrophic)

Sodium, calcium, potassium and chlorine channels are all controlled by what mechanism?

Voltage gating

What is the patch clamp method?

Using a recording pipette, suction is applied to a specific site and an ion channel is taken off of the cell body (or whatever other structure is being looked at). Inside out or outside in methods allow for different analyses of ion channels

What will be observed in the patch-clamp recording of a sodium channel?

The channel will briefly open which allows for inward current of sodium but this is quickly stopped as the inactivation mechanism is applied in a short matter of time

Inactivation of sodium channels is (blank) of time and voltage

Dependent

If you run a patch clamp experiment through a single sodium channel multiple times and add the results together, what will you eventually see?

The sum of the graphs put together will replicate the sodium current observed throughout the whole cell, not just from one single channels

In sodium channels, "de-inactivation" is what?

Voltage dependent

The functional state of potassium channels is purely based on what?

The mathematical function of voltage

When a current is run through a single potassium channel using the patch cell method, what is observed?

The sum of the currents, when added together, exactly resembles that of a whole cell experiment for potassium in that there is a delayed response, continued action and then quick, immediate deactivation

Give a general description of the structure of a voltage-gated ion channel

There are 4 repeating subunits and 6 segments to each: 3 outer sections, a 4th cut-in section which acts as a voltage sensor and then segments 5 and 6 which form the central ion channel

How does a delayed rectifier potassium channel differ from a type A K channel?

The type A channels quickly spike in conductance then quickly fall back down while the delayed rectifier remains high in conductance then almost immediately cuts back down

Compare the closing of sodium channels to type A potassium channels

They are very similar in that a ball-and-chain model mechanism comes in to close the channel in both cases

How can the gap between the QT phases of cardiac/neuronal charging be impacted by potassium recharging?

The interval is spread out which can lead to cardiac arrhythmia which in turn can lead to fainting, seizures and sudden death

What potassium channel type gives rise to AHP (after hyper polarization) and regulates cell excitability?

Calcium-activated potassium conductance

In ion channel proteins, how are selectivity filters formed?

Pore loops form a narrow pore that has 4 binding sites for its respective ion, typically potassium

How do the selectivity factors in potassium channels work?

Amino acids in the inner cavity destabilize the water shell around potassium allowing them to interact with the structure; sodium is not capable of having its water shell manipulated through this same way

How does the S4 voltage sensor respond to depolarization?

It is attracted to membrane potentials over -60mV and then flips up out of the membrane resulting in a complete conformation shift which opens the inner ion channel

Comparing the sequences of the same type of channel from different species to find regions of high similarity and comparing sequences of different but related channels from the same species are both methods for what?

Identifying functionally important domains

What effects can mutated genes, antibodies/toxins and abnormal transcription of normal genes have on ion channels?

They can result in abnormal or absent channel proteins, irregular binding to channels or aberrant expression of normal proteins (respectively) which can all lead to various channelopathies

How do nerve injury and neuropathic pain impact neuronal signaling and what sodium channels are modified as a result?

They can induce electrical hyperexcitability; Na1.8 and Na1.9 expression is down-regulated while Na1.3 expression is up-regulated

How could sodium channel clustering at the site of an injury lead to chronic pain?

The increased hyperexcitability could result in higher firing rates and larger depolarization of neurons

Are genetic changes in ion channels of neurons typically autosomal dominant or recessive?

Dominant

How do anti-seizure medications help to alleviate symptoms?

They act as agonists on GABA receptors which in turn increase chloride influx which adds to hyperpolarization