L1 Synaptic Transmission Flashcards
Which type of synapse forms the majority?
Chemical synapses
What are the 6 differences in electrical synpases?
oSimpler structure and function
oFaster
oPassive signal transmission
oBidirectional
oMinority, but particularly common in development
oAllow synchronised electrical activity among populations of neurons
label the type of synapse
What type of neuron is shown?
(a) axodendritic
(b) axosomatic
(c) axoaxonic
Label the diagram of a chemical synapse
Label the neuromuscular junction
What happens to neurotransmitter molecules when an action potential reaches the synaptic terminal?
On an action potential reaching the synaptic terminal, neurotransmitter molecules are released from the presynaptic neuron and diffuse across the synaptic cleft to the postsynaptic membrane.
What are the 2 possible responses that can be initiated when receptors recognise the neurotransmitters?
1) Direct excitatory or inhibitory neurotransmission - the membrane of the next cell becomes slightly depolarized or hyperpolarised.
2) Neuromodulation - alters the presynaptic cell’s ability to release more transmitter or the postsynaptic cell’s ability to respond
What are the 4 criteria that define a neurotransmitter?
1) synthesized in the neuron
2) present in presynaptic terminal and released in amounts sufficient to exert a defined effect on the postsynaptic neuron or effector organ.
3) when administered exogenously (as a drug) it mimics the action of the endogenously released transmitter.
4) a specific mechanism exists for removing it from the synaptic cleft
fill in the gaps on Synaptic vesicle release and recycling
Pool of vesicles above the active zone is anchored to the cytoskeleton by __________
- Action potential to presynaptic terminal, _________ channels open, ________ flows into the cytoplasm
- _______ activates _________ which phosphorylates _______.
___________ can no longer bind to the cytoskeleton, vesicles dock to the _________
Pool of vesicles above the active zone is anchored to the cytoskeleton by synapsin
Action potential to presynaptic terminal, voltage gated Ca2+ channels open, Ca2+ flows into the cytoplasm
Ca2+ activates Calcium calmodulin activated kinase II (CaMKII) which phosphorylates synapsin.
P-synapsin can no longer bind to the cytoskeleton, vesicles dock to the active zone
Label the stages of Synaptic vesicle release and recycling
How does Synaptic vesicle release and recycling happen?
SNARE* complex at active zone docks vesicles to the plasma membrane
What is this?
SNARE protein
complete the diagram
During Synaptic vesicle release and recycling, vesicle membrane is rapidly recovered via __________, new vesicles bud off and are refilled with ____________
vesicle membrane is rapidly recovered via ENDOCYTOSIS, new vesicles bud off and are refilled with transmitter
What are the 2 deadliest toxins?
Botulinum toxin (BoTX)
Tetanus toxin (TeTX)
What do clostridial toxins target?
Sites of proteolysis that blocks neurotransmitter release.
Cleavage of SNARE proteins by clostridial toxins
Where does Botulinum toxin (BoTX) target?
neuromuscular transmission ACh - paralysis
Where does Tetanus toxin (TeTX) target?
interneurons at spinal cord, GABA, Gly - muscle rigidity
Both Botox and Tetanus prevent __________ release
Botox and Tetanus – prevent transmitter release
Which bacteria do botox and tetanus come from?
(from bacteria Clostridium botulinum and tetani respectively)
What does botox cause?
Botox acts directly at the neuromuscular junction. The muscles lose all input and so become permanently relaxed.
What can botox be used to treat?
treatment of muscle spasms
what does tetanus cause?
Tetanus toxin inhibits the release of Glycine and GABA at inhibitory neurons, resulting in dis-inhibition of cholinergic neurons, which causes permanent muscle contraction.
List 5 different diseases that affect the presynaptic terminal
What are vesicular transporters powered by?
Proton gradient
ATPase proton pump loads up vesicles with H+ making vesicles acidic (pH5.5) compared to neutral pH of cytoplasm (pH7.2)
e.g. 1 glutamate traded for 1 H+ (counter-transport mechanism)
What are plasma membrane transporters powered by?
electrochemical gradient
[Na+] higher outside / [K+] higher inside
Glutamate co-transported with 2 Na+
What are the 2 types of membrane transporters and what do they transport?
Vesicular transporters powered by proton gradient
Plasma membrane transporters powered by electrochemical gradient
(amino acids, amines and ACh)
Label the diagram on the role of glia
What are the 3 main functions of glia?
They express neurotransmitter receptors, which allows them to respond to synaptic activity by changing intracellular levels of Ca2+
They coordinate synapse formation and elimination with secreted and cell-surface associated signals
They control synapse formation, function, plasticity and elimination. They are crucial during development, for learning and memory, as well as in disease.
What does this show?
The tri-partite synapse
Synapse + astrocyte process
Name 6 diseases glia are involved in
Reactive gliosis following injury (relevant for CNS regeneration potential)
Role in aberrant synapse formation, linked with epilepsy and neuropathic pain
Brain cancer
HIV-induced dementia
Neuroinflammatory response of depression
Other neurodegenerative diseases, such as Alzheimer’s, glaucoma and prion disease, through aberrant synaptic stripping
