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17 Cards in this Set

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What is the process of an excitatory postsynatpic response?
Opening of cation-selective channel
--> excitatory current (EPSC) --> depolarizing excitatory potential (EPSP)
What is the process of an inhibitory response?
Opening of Cl-selective GABA channels or K-selective ion channels
--> inhibitory current (IPSC) --> Inhibitory potential (IPSP)
What determines the firing probability of an individual neuron?
Simultaneous excitatory and inhibitory inputs
What type of potentials are always found at the NMJ?
Always excitatory
What are ionotropic receptors?

What is the structure?
Ligand-gated ion channels that mediate fast changes in postsynaptic (5-30 ms) excitability

Made up of 5 subunits around pore
What makes an ionotropic receptor excitatory vs. inhibitory?
Excitatory: cation selective

Inhibitory: Cl-selective (GABA and glycine receptors)
What do metabotropic receptors do?

How are they formed?
Mediate slow changes in postsynaptic excitability (hundreds of ms)

Formed from single seven-transmembrane domain polypeptides coupled to G-proteins
What are the steps for metabotropic receptor activation? (4)
1. NT binds receptor
2. GTP binds to receptor, beta and gamma subunits leave
3. Ga activates effector protein
4. Intermediate steps --> open or close ion channels
What is the nicotinic Ach receptor?

What does it mediate?
Ligand-gated ion channel at the NMJ

Mediates fast synaptic transmission
What does the snake toxin alpha-bungarotoxin do?
Bind to and blocks nicotinic ACHR --> muscle paralysis
What is the process of nicotinic ACHR activity?
Ach binds --> increases open potential of receptors (for msecs)--> individual channels let cations in --> summation of channels leads to EPSC --> depolarization --> AP
How does Erev determine whether a channel is excitatory or inhibitory?
Erev < threshold = inhibitory
Erev > threshold = excitatory
What happens to Erev when...

a. [Na]ec decreases
b. [K]ec increases
a. Erev gets more negative
b. Erev gets more positive
What is the permeability of nAchR to K and Na?
Equal permeabilities
When is PSP depolarizing?
Erev > Vmem
When is PSP hyperpolarizing?
Erev < Vmem
What drives the current at negative potentials?
Na in --> depolarizing