Synaptic Transmission Flashcards
What are the types of synapses?
electrical and chemical
this type of synapse has gap junctions between neurons
eletrical
electrical synapse main protein
connexins
this type of synapse has a narrow intercellular gap
electrical
in what direction do electrical synpases occur
both direction
which type of synapse has a synaptic delay
chemical
in what direction do chemical synapses occur
one direction
Charcot marie tooth is csused by a mutation in one of the _____ genes expressed in the Schwann cells disease:
connexin
what type of synapse does CMT disease occur in
electrical - ionic gap junctions
charcot marie tooth symptoms:
impaired myelination
peripheral - motor and sensory
foot drop
not fatal
sequence of events at chemical synpase
AP - calcium enters - transmitter release - binds to receptor - open close ion channels
what is Ca2+ buffering?
Ca2+ accumulates in presynaptic terminal
proteins involved in vesicle docking:
SNARE:
syntaxin
SNAP-25
synaptobrevin
targets nicotinic cholinergic terminals at NMJ
botox
targets glycinergic inhibitory terminals
Ttx
what is synaptotagmin?
calcium sensor
specific protease that cleaves SNARE proteins associated with the vesicular and presynaptic cell membranes
botulinum and tetanus
this toxin occurs after open wounds and takes up inhibitory spinal interneurons
tetanus
this toxin affects motor nuerons
botulinum
what proteins are involved in vesicle recycling?
clathrin and dynamin
what is synaptic fatigue?
synaptic depression -prolonged stimulation of synapse decreasing # of vesicles
inward current of transmitters causes
depolarization - excitatory
outward current of transmitters causes
hyperpolarization - inhibitory
how can transmitter be removed by synaptic cleft?
diffusion, uptake or enzymatic degradation
what is enzymatic degradation
Ach hydrolysed by acetylcholinesterase
what does the NMJ release
Ach - nicotinic Ach receptor
what are postsynaptic potentials
graded potentials - size decreases
Muscle weakness due to reduced functional ACh receptor be a symptom of
Myasthenia gravis
Myastenia gravis symptoms
droopy eyelids, limb muscles weakness
MG treatment
inhibitory acetylcholinesterase and removal of thymus
disease associated with carcinoma of the lung and reduced Ach release
Lambert-eaton
what does lamber eaton syndrome do to channels
produces antibody against voltage gated calcium channels
what are the postsynaptic receptor types
- ion gatted channels
- g-protein coupled receptors
Neuromuscular junction receptor
nicotinic acetylcholine receptor
Permeable to cations (mostly Na+, K+, small amounts of Ca2+). Not as selective as the voltage gated channels
nicotinic Ach receptors
Prolonged exposure to ACh causes
desensitization (inactivation) of Ach receptor
high doses of Ach can cause
muscle paralysis
carries most of the excitatory current through the ACh receptor ion channel
Na+
Individual ligand gated receptor channels can be studied with
psthc clamp recording opened in ach presence
ionotropic glutamate receptors have two major classes:
AMPA and NMDA
synthetic drug agonist
* Most common receptor in the CNS
AMPA
permeable to Na and K
AMPA
permeable to Na and Ca
NMDA
which receptors are dually regulated
NMDA glutamate receptors
depolarization of NMDA removes which blocking channel
Mg2+ ion blocking channel
receptor important in learning and memory formation
NMDA
glutamate toxicity is:
Excessive Ca2+ or glutamate entry can be harmful to neurons
glutamate toxicity causes:
strokes, epileptic seizures, neurodegenerative diseases like Huntingtons chorea and ALS
inhibitory transmitter in spinal interneurons
glycine
major inhibitory transmitter in brain
GABA
inward flow of Cl- ions
Cl- permeability caused by inhibitory transmitters
Which drugs can bind to GABA receptors and increase their inhibitory function
Benzodiazepines
Barbiturates
prescribes for anxiety
valium and librium
Proteins with 7 transmembrane regions activate:
G-protein receptors
Most transmitters use _____ coupled receptors
G-protein
Examples of G-protein transmitters
serotonin, dopamine, norepinephrine, histamine
Synapse of multiple sites for pharmacologic intervention
seronotin synapse
which is the serotonin channel
5-HT3