Lecture 14: Communication with Ionotropic Receptors

What are ionotropic receptors and how can they be studied?

They are ligand-gated ion channels and can be studied via patch clamp techniques

Instead of referring to muscles as synapses, what do we refer to them as?

End plate currents and end plate potentials

When do the end plate currents and end plate potentials occur in muscles?

When it receives acetylcholine

How do we identify EPC?

We look for reversal potentials by removing extracellular concentrations of the ions

Is an inward current negative or positive?

It is negative

As the post synaptic membrane potential in a muscle cell increases, the EPC…

has a greater amplitude

How do we figure out which ion the membrane of a cell is permeable to?

By matching the membrane potential with the reversal potential

What does it mean when the reversal potential is not at one ion?

That the cell membrane must be permeable to more than one ion

Does the voltage of the presynaptic cell gave to change in order for a ligand gated ion channel to open?

No, only has to produce a synaptic or change in potential

What does it mean to be cat-ion non-specific?

It means that you have an excitatory ionotropic receptor that allows multiple types of cations to move in and out of it

What always happens when the membrane potential is above the action potential threshold and where does this decision occur?

We fire and the decision occurs right in the cell body or axon hillock

Excitatory postsynaptic potential

a potential change driving the membrane above the action potential threshold potential

Inhibitory postsynaptic potential

a potential change driving the membrane below the action potential threshold

Do EPSP’s and IPSP’s come in constantly or one at a time?

constantly

What are the two things that determine whether a potential is excitatory or inhibitory?

* reversal potential of the ions that are conducted
* threshold potential of the neuron (usually around -40mV)

If the reversal potential is below the threshold potential, it’s…..

Provide two ion examples

inhibitory

* k+,Cl-

if the reversal potential is above the threshold potential it’s…

provide an example

excitatory

* cation non-specific ion channels

When is the reversal potential the same as the equilibrium potential?

When the cell is only permeable to one ion

Is glutamate excitatory or inhibitory? Why?

Excitatory because it pushes the cell above the threshold potential

Is GABA excitatory or inhibitory? Why?

Inhibitory because it never allows the cell to exceed the threshold potential

Temporal Summation

Any two postsynaptic potentials that occur at the same time will build on each other and are more likely to produce an action potential

Spatial Summation

iThe closer electrical potentials are to the cell body and particularly the axon hillock, the more influential they will be (more likely to produce an action potential)

Where in the cell are inhibitory potentials more commonly found and why?

They are more commonly found right at the cell body or root of the dendrite because their job is to veto so they need to be spatially influential