chemical synaptic transmission SEM1 Flashcards
(41 cards)
what is the criteria that define a neurotransmitter
A)Presence at Synapse: Must exist in the synapse with pathways for its synthesis.
B)Calcium-Dependent Release: Released upon stimulation (like a pre-synaptic action potential) through a mechanism dependent on calcium ions.
C)Specific Receptors: Must have specific receptors on the post-synaptic cell
what is end plate potential (EPP)
the conversion of an electrical signal in the nerve into a mechanical response in the muscle resulting in muscle contraction
what do NMJ function with
high safety factor
what does the safety factor at the NMJ ensure
ensures the end plate potentials (EPPs) are much larger than required for reliable muscle action potential generation
what is the normal response of calcium entering a neuron
action potential triggers chain reaction => calcium enters neuron => promotes release of acetylcholine => imitating muscle contraction
what occurs if tetrodotoxin blocks the initial action potentials in neuron
chain reaction leading to calcium entering neuron is halted preventing muscle contraction
what are the 4 main steps of calcium induced vesicle fusion and neurotransmitter exocytosis at a synapse
1)vesicle docks
2)SNARE complex formation
3)calcium entry
4)membrane fusion and neurotransmitter release
what occurs during vesicle docking during Ca2+ induced vesicle fusion
neurotransmitter vesicles attach to presynaptic membrane with SNARE proteins (e.g syntaxin and SNAP-25)
what occurs during SNARE complex formation during Ca2+ induced vesicle fusion
SNARE proteins tightly bind together pulling the vesicle and presynaptic membrane close for fusion
what occurs during calcium entry during Ca2+ induced vesicle fusion
voltage-gated calcium channels open due to incoming action potential, allows Ca2+ ions to enter and bind to synaptotagmin on vesicle
what occurs during membrane fusion and neurotransmitter release during Ca2+ induced vesicle fusion
calcium-bound synaptotagmin triggers fusion of vesicle w/ presynaptic membrane => release of neurotransmitters into synaptic cleft to signal next neuron
what is the function of SNARE proteins
mediate the fusion of vesicles containing neurotransmitters, hormones etc w cell membranes to release their contents
what is the process of vesicular exocytosis and recycling at a synaptic terminal
1)brief stimulation of presynaptic terminal
2)washing away extracellular HRP
3)formation of clathrin-coated pits
4)recycling and reformation of synaptic vesicle
5)continuous cycle of endo and exocytosis
At the NMJ what does acetylcholine bind to
Binds to post-synaptic nicotinic acetylcholine receptors (nAChR)
What are nicotinic acetylcholine receptors (nAChR)
nAChR are ligand-gated ion channels
How is acetylcholine cleared from the synaptic cleft
By the enzyme acetylcholinesterase
What does the enzyme acetylcholinesterase do
Hydrolyses acetylcholine to choline and acetate
What are combined together to synthesise acetylcholine
Acetyl CoA and choline are combined by the enzyme choline acetyltransferase (ChAT)
What are the two types of synaptic communication
Electrical and chemical synapse
what is Dale’s law
the same neuron uses the same set of neurotransmitters at all of its synapses
what occurs at the axon hillock
low threshold action potentials originate here
What is the process of synthesis and release of glutamate in the brain
1)synthesis of glutamate
2)storage and release
3)reuptake and recycling
4)modulation
What is L-glutamate
Major ‘fast’ excitatory neurotransmitter in the mammalian CNS
What is glutamate
Amino acid
