Lecture 34 - Synapses Flashcards
What is a synapse
junctions that mediate transfer of information
pre-synaptic
neuron conducting impulse towards synapse (sender)
post-synaptic
neuron conducting impulse away from the synapse (receiver)
Synaptic cleft
space between neurons
neurotransmitter
chemical messenger of electrical impulse across synaptic cleft
receptor region of postsynaptic neuron
receives neurotransmitters via specialized receptors
what is the most common type of synapse
chemical synapse
Electrical synapse
neurons are electrically couples and joint by gap junctions, can be bidirectional
axon terminal of presynaptic neuron
contains vesicles filled with neurotransmitters
what type of synapse is abundant in embryonic nervous tissue
electrical
what kind of communication is used by electrical synapses
rapid
Large neurotransmitters are made in _____ while small neurotransmitters are made in _____
cell body; terminals
what are considered large neurotransmitters
peptides
what are considered small neurotransmitters
- acetylcholine
- biogenic amines
- amino acids
Synaptic vesicles
uptake, store, and release neurotransmitters
spherical, membrane-bound organelles
Summarize neurotransmitter release
1 - 3. Neurotransmitter synthesis and packaging in vesicle
4. formation of reserve pool vesicles
5. Ca2+ entry in response to AP
6. Vesicle mobilization to the active site
7. docking, fusion, and exocytosis of neurotransmitter
8. vesicle endocytosis
Fusion of vesicle to plasma membrane depends on
SNARE proteins
what acts as an intracellular messenger at the axon terminal
calcium
What are the 4 steps for vesicle fusion
- Docking (at active zone)
- Priming (ATP dependent)
- Fusion (SNARE and calcium)
- Release
when does signal termination occur
neurotransmitter levels fall
how can neurotransmitter levels fall to terminate signals
- reuptake
- enzymatic degradation
- diffusion
what are neurotransmitters classified by
function and chemical structure
What 3 effects do neurotransmitters have
- excitatory
- inhibitory
- neuromodulatory
what are the 2 actions of neurotransmitters
- direct (bind to channel)
- indirect (use of secondary messengers)
give an example of inhibitory neurotransmitters
GABA and endorphins
what determines a neurotransmitter’s effect
receptors
give an example of excitatory neurotransmitters
glutamate, epinephrine, norepinephrine
give an example of neuromodulatory neurotransmitters
serotonin and dopamine
Acetylcholine (ACh)
- commonly used at the neuromuscular junction
- synthesized by acetyltransferase
- degraded by acetylcholinesterase
Catecholamines are derivatives of what amino acid
tyrosine
examples of catecholamines
dopamine, norepinephrine, epinephrine
serotonin is a derivative of
tryptophan
histamine is a derivative of
histidine
what are proven neurotransmitters
- glutamate
- aspartate
- glycine
- GABA
Endocannabinoids
naturally occurring, lipid-based
neuromodulatory
Purines
monomers of nucleic acid
adenosine/ATP
Gas/Lipid neurotransmitters
nitric oxide, carbon monoxide
Summarize what happens at the neuromuscular junction
- ACh binds to receptors on the sarcolemma
- Na+ flux
- action potential generated
- potential travels down T-tubules
- calcium release
- cross-bridge cycling
how does tetanus cause a permanent excitatory state
invade inhibitory interneurons (cleaves SNARE protein)
vesicles don’t fuse
