synaptic transmission and neurotransmitter release Flashcards
what is a synapse
neuroanatomical structure that permits communication between a neuron and its target cell
what is a synaptic cleft
physical gap between neuron and target cell
what are the 3 types of synapses
- axodendritic
- axosomatic
- axoaxonic
why are neurotrasnmitters stored in vesicles
- quantal release
- protection from degradation
- conservation (many NT are recycled)
what are the 4 steps in vesicular release
- action potential
- calcium entry
- membrane fusion
- endocytosis
how does calcium enter the synaptic terminal
- through voltage-gated calcium channels
- these are the N-type channels
- concentrated at active zones
what does the proton pump do
creates a proton gradient across the synaptic membrane
what do transmitter transporters do
uses energy of proton gradient to transport NTs into vesicles
what occurs when there is release from cytoskeleton
- action potential reaches the terminals
- causes voltage-sensitive calcium channels to open
- intracellular calcium concentrations increase
what is calcium-dependent phosphorylation of synapsin
causes the vesicles to detach from microfilaments (from cytoskeleton)
what are snares
vesicular (v-snare) vs terminal (t-snare)
what does snap-25 do
(t-snare) regulates the assembly of snares that tether the vesicle to the presynaptic membrane
what does synaptotagmin do
(v-snare) is a Ca2+ sensor and catalyzes membrane fusion
what are some effects of toxins on NT release
- tetanus toxin damages synaptobrevin
- botulinum toxins damage t-SNAREs and V-SNARES
what are 3 sources of botulism toxin
- toxicoinfectious botulism (grows in intestinal tract - often in foals)
- ingestion of preformed toxin (animal ingest contaminated feed, any age affected)
- infection in wounds (rare)
