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What determines if Ach will act in an excitatory or inhibitory manner?
the type of ion channel on the post synaptic membrane
Source of Ach in the CNS?
Degeneration of Nucleus Basalis leads to/?
What happens in Presynaptic Facilitation?
nt decreases k+permeability, trapping k+inside the cell..effectively depolarizing the membrane so upon AP the membrane is dopolarized to +45 instead of +35
Short-term memory is characterized by what?
Presynaptic Ca +2
What happens in presynaptic inhibition?
Cl - permeability increased...hyperpolarizing the membrane...no depolarization
Ion channels are exclusively present where on the neuron?
On the Axon
What limits the frequency of AP?
Absolute Refractory Period
Post synaptic potentials are voltage or ligand gated?
What nt is always excitatory in the CNS?
Whats the difference between an Ionotropic and metabotropic nt receptor?
Ionotropic--nt binding opens an ion channel--quick
Metabotropic--nt binding activates a series of 2nd messengers which opens the ion channel..long activation..long duration
Polio selectively affects what?
LMN in Lamina 9
What is the mode of action of a botulism toxin?
B. toxin prevents release Ach from the presynaptic membrane
A tumore in the cerebropontine angle affects what CN?
Auto-immune--ab against Ach receptors...paralysis..
Diagnosis---Endrophonium(short acting- anticholinesterase
Treatment--Neostigmine(long lasting anticholinesterase)
Whats the cure for Myesthenia Gravis?
What is the mode of action of Sarin Gas
A lesion where would produce a toxic gait?
A lesion in the midbrain region of the brainstem would produce what deficit?
CN III lesion---can't adduct eye
A lesion in the pons region of the brainstem would produce what deficit?
Lesion of CN VI---can't abduct eye
A lesion in the medulla region of the brainstem would produce what deficit?
CN-XII---ipsilateral deviation of tounge
Absolute refractory period is due to?
What prevents the Action Potential from being bidirectional?
Absolute refractory Period
deposition of iron
Disease caused by hemosiderosis