L6: Synaptic Transmission Flashcards
What are the 4 criteria for a chemical NT to be considered a chemical NT?
- present in presynaptic terminals
- release in response to stimulation (release must be Ca2+ dependent)
- specific receptors present on post-synaptic cell
- mechanism to inactivate NT must be present
What are some steps of chemical neurotransmission?
1 - transmitter is synthesized & in vesicles
2 - A.P invades presynaptic terminal
3 - depolarization opens voltage-gated Ca2+channels
4 - influx of Ca2+ thru channels
5 - Ca2+ causes vesicles to fuse w/ presynaptic membrane
6 - release of NT into synapse
7 - NT binds to receptor in post-synaptic membrane
8 - opening or closing of post-synaptic channel
9 - removal of NT
What are 5 characteristics of chemical synapses, which are more common in CNS than electrical synapses?
- directionality
- amplification
- potential for excitation & inhibition
- potential for plasticity
- integration in space & time
How are synaptic facilitation and temporal summation different?
Synaptic facilitation occurs in pre-synaptic terminal while temporal summation occurs in post-synaptic terminal
What is and what produces synaptic facilitation?
- synaptic facilitation is a form of short-term synaptic plasticity in which 2 or more A.Ps invade pre-synaptic terminal causing a rapid increase in synaptic strength
- due to prolonged elevation of pre-synaptic Ca2+
Why is it that Ca2+ can build up in the nerve terminal?
b/c entry of Ca2+ is rapid, clearance is slow
What type of NT release (small molecules vs peptides) occurs when there is a low frequency stimulation?
When there’s a low frequency stimulation with a localized increase in Ca2+, there will be a preferential release of small molecule NTs.
What type of NT release (small molecules vs peptide NT) occurs when there is a high frequency, diffuse increase in Ca2+ stimulation?
When there’s a high frequency stimulation with diffuse increase in Ca2+, both types of NTs will be released.
T/F: One neuron can only release 1 NT.
False; 1 neuron can release 1 or more NTs
What proves that NT release is quantal?
release of many quantal packets of Ach each produces miniature endplate potentials (MEPPs), which togethr produces EPP that depolarizes target cell. It is known that the size of MEPP is proportional to vesicle’s Ach content.
At most glutamate-mediated synapses, EPSP is a sum of which 2 components?
1) rapid component mediated by AMPA receptor that is always firing
2) slow component mediated by NMDA receptor which only fires when there’s Ca2+, glycine, glutamate, and depolarization to get Mg2+ off receptor.
What are barbiturates?
a class of CNS depressants
- GABA elicits larger IPSP
- increase GABA = relaxing, anti-anxiety & anti-convulsive effects
GABA binding to GABA receptors result in EPSPs or IPSPS?
hyperpolarization = IPSPs
