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Unformatted text preview: dium in) and
increase driving force (move potassium out), so there's no net effect. one compensate the other.
threshold is the level when you depolarize a lot so total inward sodium current exceed the
outward potassium current.
-if transmitter open potassium channel: have more outward potassium current (positive driving
force), make membrane potential closer to Ek
-if transmitter open chloride in: most neuron ECL is more negative than resting potential. so
open chloride channel: 1. if conductance/permeability of ion increase, ion approach Ek of cell 2.
driving force (subtract,,.) get a positive=outward current (always hyperpolarize), outward current
is inward movement of chloride. Responses of Postsynaptic Cells Chemical synapse
inhibit: increase total outward current, move threshold to
higher potential. glycine+GABA are inhibitor transmitter,
act by open chloride or potassium channel.
-closing of ion channel: if it's sodium channel that's close,
cut off inward current, result in hyperpolarization.
-potassium (formerly open, out K, hyper): cell would
depolarize and excite Fig. 8-23 defects in synaptic transmission:
-most mental disorder (depression, schizophrenia, nicotine/drug abuse), neurological disease
-neuromuscular junction: synapse between nerve and skeletal muscle. severe muscle weakness (myashenia). autoimmune disease. produce antibody
against body's own nicotinic ACh receptor (ionotropic receptor for
acetylcholine). ACh would have open a pore that is permeable to sodium and
potassium, which will flow in opposite direction with sodium will come in and
potassium will come out. this means that inward sodium movement will be
greater than potassium outward, sodium is more out of equilibrium than
potassium. membrane potential is farther away from Ena (big inward current
add small outward current=big current). depolarize.
neuromuscular junction have very strong synapse. AP is always trigger.
ptosis is dropping of of eyelid
dipopia: two eyes looking different place. can't look at two same place.
both muscles are weaken. the synapse is weaken. if you take biopsy tissue.
when you depolarize, trigger AP. stimulate the nerve see AP don't line up. not
all signal are AP. EPSP is weak, barely make past threshold, so there's a delay.
(so it either don't work or there's a delay.
metabotropic the other ACH R. Myasthenia Gravis
put a drug that prevent degradation of acetylcholine Single Fiber
Electromyography Normal Ptosis & Diplopia
+10 Normal MG after Tensilon
failure of transmission mV -80
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- Spring '09