Synapse Flashcards
synapse
synapse are junctions between neurones
synaptic cleft is the gap between two neurones
excitatory synapse
action potential arrives at synapse
triggers Ca+ ion channels to open and Ca+ enter
causes vesicles to fuse with pre synaptic membrane
NT diffuses across synapse
NT binds to complementary receptors on the post synaptic membrane
triggers Na+ VGIC to open and Na+ enter
if depol reaches threshold then an action potential will form
inhibitory synapse
NT binds with post synaptic membrane
triggers chloride ions to enter PSM through chloride ion protein channels
triggers K+ VGIC so K+ diffuse from PSM into synaptic cleft
makes membrane hyperpolarised
more Na+ are needed to reach threshold and depol so an action potential is not generated
spatial summation
lower frequency action potential can hit threshold in next neurone if they create an accumulation of NT in the synaptic cleft, enough to depol and reach threshold
merging of many synaptic knobs at a PSM
effects NT are combined
if there are inhib and excit then they may cancel each other out
if there are more excit than inhib then an act pot will be generated
drugs- stimulate
increase amount of excitatory NT in synaptic cleft
mimic the neurotransmitter- same shape so binds to receptors
inhibit the enzyme that breaks down NT
increase the release of the NT into the synaptic cleft
drugs- inhibit
increase amount of inhibitory NT in synaptic cleft
mimic the neurotransmitter
inhibit the enzyme that breaks down the NT
increase the release of the NT
examples
epilepsy- caused by an increase in activity in the brain eg insufficient GABA which is an inhibitory NT
vigabitrin has similar structure and binds instead
serotonin is involved in regulation of mood, drugs can increase levels of serotonin eg prozac
stopping transmission
enzyme specific to NT will break down NT
products will be actively transported back into pre synaptic membrane
temporal summation
act potentials arrive quickly after eachother
lots of NT is released into synaptic cleft
enough released to depot membrane and generate an action potential
unidirectional impulse
vesicles with NT are only found at synaptic knob
NT receptors only on post synaptic membrane
impulse travels in one direction
