L8 Synaptic Transmission Flashcards
What is another term for electirical synapses?
Gap junctions
Which is faster: gap junctions/electrical synapses or chemical synapses?
Gap junctions/electrical synapse
What links the adjacent cells in gap junctions?
Little tunnels called connexons
Where are gap junctions abundant?
Cardiac muscle and single-unit smooth muscles
What is synaptic delay?
The time needed for the conversion of the electrical signal from the presynaptic neuron to an electrical signal in the post synaptic neuron by chemical means. (0.5-1 msec)
What happens when the action potential reaches the end of the axon?
Calcium channels open and let calcium in to the presynaptic knob.
(Remember there is 10k times more calcium outside than inside the cell)
Once calcium comes in to the presynaptic knob, what happens?
Calcium binds to vesicles full of neurotransmitters and tell them to release their contents into the cleft
Which type of post synaptic receptor is faster: ligand gated ion channels or G-Protein coupled receptors?
Ligand-gated ion channels have faster transmission
What are three ways to get the neurotransmitter out of the cleft and end the signal?
- Diffusion away from cleft
- Enzymatic degradation
- Reputake into the presynaptic axon
What is the only neurotransmitter in the neuromuscular junction?
Acetylcholine
How long is the synaptic delay
0.5 msec
What is the end result of ACh being released into the cleft?
Binds to ligand gated Na+ channels, creating a graded potential, and then triggering an action potential once the post synaptic cell gets to -55mV
When calcium rushes into the presynaptic knob, what does it bind to?
Binds to one of the SNARE proteins (synaptotagmin) on the vesicle and then the SNARE protein allows it to dump its contents into the cleft
WHat happens to ACh after AChEsterase degrades it?
Gets broken down into acetic acid and choline
Choline is then pumped back in to the presynaptic cell and acetic acid is thrown away
What neurotransmitter is used at the excitatory adrenergic synapse?
Norepinephrine
Aka noradrenaline
What is the end result of norepinephrine being released into the cleft?
It binds to a G-Protein coupled receptor that activated Adenylate Cyclase, which makes cAMP, which THEN activates a ligand -gated sodium channel, depolarizing the cell
What is the neurotransmitter used in a GABA-ergic synapse?
GABA
What is the end result of GABA being released into the synapse?
GABA binds to Cl- channels, which lets Cl- into the postsynaptic cell, making it even more negative and less likely to fire.
Remember Cl- is higher outside the cell
