Wagner Flashcards
Axoplasmic resistance
increasing axon diameter decreases axoplasmic resistance and increases conduction velocity
Myelin
decreases membrane capacitance and increases conduction velocity
TTX sensitivity
inhibits voltage-gated Na channels –> no depolarization
results in flaccid paralysis;
due to tyrosine and glutamate residue in the loop between S5 and S6 of repeat1
Na selectivity
due to collective interaction between S5, S6 and intervening loop;
critical residues include lysine of repeat III and alanine of repeat IV
Determinants of activation
arginine and lysine at every third position of S4 enables S4 to act as a voltage sensor
TEA sensitivity
inhibits voltage-gated K channels –> prolonged depolarization;
results in rigidity/tetanus;
due to consensus sequence w/n H5 loop
Pore formation
H5 loop lines the pore; S6 cytoplasmic loop linking S4 and S5 forms pore mouth
Na channel inactivation
due to isoleucine, phenylalanine, methionine residues of cytoplasmic loop
K channel inactivation
N-type (fast): inactivation ball at N terminus interacts w/cytoplasmic loop b/n S4 and S5 to form inactivation gate
C-type (slow): C-terminal undergoes conformational change
Ca channel inactivation
at S6 of repeat 1;
C-terminus there is Ca dependent inactivation
Postsynaptic anatomical features
enriched w/postsynaptic receptors;
four elements that may be contracted: dendritic spines, proximal dendrites, soma, another axon terminal
Type I Synapse
asymmetric excitatory synapses; wide synaptic cleft; dense projections
Type II Synapse
symmetric inhibitory synapses; narrow synaptic cleft; fewer dense projections
En passant synapses
intermittent presynaptic axonal swellings;
greater separation b/n presynaptic and postsynaptic elements;
no postsynaptic specializations;
transmission is diffuse and sluggish
Synaptic vesicles
derived from endosomes;
express neurotransmitter transporters;
can be filled with neurotransmitter