Oct. 13: 2.2 Flashcards
How many synaptic inputs does a neuron receive in chemical synaptic transmission?
tens of thousands to hundreds of thousands
Compare versatility of chemical to electrical synapses
Chemical is more versatile: FIRES melt Plastic fast synapses inhibitory tsmission regulation excitatory tsmission slow synapses plasticity
Experiment demonstrating existence of chemical synapses/ neurotransmitters
Otto Loewi
Stimulate one frog heart electrically through vagus nerve, then add perfusate to another heart. This heart slows down.
Speeds up heart rate
sympathetic stimulation
Slows down heart rate
parasympathetic stimulation/ vagus nerve
Why heart beats by itself in saline
pacemaker cells
chemical which slows down heart rate
acetylcholine
Types of NT receptors in chemical tsmission
ionotropic
metabotropic
Effects of metabotropic receptors
cascade of biochemical events culminating in the opening or closing of certain ion channels and a change in membrane potential
PSD
post-synaptic density
proteins needed for NT clustering and synaptic function
Active zones
where vesicles are docked at presyn membrane
calcium entry at terminals triggers
fusion of vesicles with membrane
EPSP produces _____ current
Inward
“Inwardly excited, outwardly inhibited”
Outward current leads to
hyperpolarization
example of effect EPSP might have w/o reaching threshold
effects voltage-gated Ca++ channels which then changes calcium signalling inside cell
Fast synaptic transmission describes transmission involving _____ receptors
ionotropic
neuromuscular junction makes good prep for study because
most neurons form synapses at spines of dendrites, which are so small an indirect reading is necessary
nicotinic versus muscarinic acetylcholine receptors
nicotinic are ionotropic
muscarinic are metabotropic
Targets acetylcholinesterase
Organophosphates such as nerve gas and insecticides
When acetylcholine is broken down, what happens to the choline?
recycled back into presyn cleft b/c of choline gradient
Curare blocks
nicotinic ACh receptors
Type of ACh receptors at neuromuscular junction
nicotinic
depolarizations of skeletal muscle fibers are called
EPPs
Vesicle cycle time: _____
1 minute
Delay between excitation of presynaptic terminal and tsmission
1ms
Time required for budding phase of vesicle cycle
10-20sec
