synaptic transmissions Flashcards
receptors only on post synaptic membranes
unidirectional
cholinergic synapse
- AP at synaptic knob of presynaptic neurone
- stimulates voltag-gated calcium ion channels in presynaptic neurone to open
- calcium ions (Ca2+) diffuse into synaptic knob (pumped out after by AT)
- causes synaptic vesicles to move to membrane and fuse
- release acetylcholine ACh into synaptic cleft (exocytosis)
- diffuse across synaptic cleft bind to specific cholinergic receptors on post synaptic membrane -> sodium channels open
- influx of sodium -> deploarisation. AP generated if threshold reached
- ACh broken down by enzyme acetylcholineesterate AChE products reabsorbed by presynaptic neurone used to make more ACh
Excitatory neurotransmitters
depolarise postsynaptic membrane - action potential if threshold reached e.g. acetyl choline in CNS
inhibitory neurotransmitters
hyperpolarise postsynaptic membrane - cant fire AP e.g. acetylcholine in heart
spatial summataions
many neurones connect to 1 neurone
neurotransmitter released from each neurone altogether reach threshold and trigger AP
temporal summation
2 or more nerve impulse in quick succession from same presynaptic neurone
AP more likely more neurotransmitter released
summation
accuratley process info
neuromuscular junctions differencs to cholinergic synapes
postsynaptic membrane had folds that form clefts which store acetylcholineesterase
more receptors
ACh always excitatory
nicotinic cholinergic receptors
drugs same shape as neurotransmitters (agonists)
mimic
more receptors activated
e.g. nicotine mimics acetylcholine
drugs block receptors (antagonists)
fewer or cant be activated
drugs inhibit enzyme
more neurotransmitter in synaptic cleft / there for longer
drugs stimulate release of neurotransmitter
more receptors activated
e.g. amphetamine
inhibit release of neurotransmiiter
fewer receptors activated
e.g. alcohol
