Neuromuscular junction Flashcards
What is a neuromuscular junction?
A specialised synapse between a motor neurone and muscle cell
How is different to a normal synapse?
The post synaptic cell is a muscle cell
What does it trigger?
Muscle contraction
What is it specialised to do?
Rapid reliable neurotransmission
Where does the motor neurone terminate?
At the motor end-plate
What specialisation can be seen at the post synaptic membrane?
Lots of folds
Meaning lots of receptors
What neurotransmitter is used?
Acetylcholine
What is synaptotagmin?
A sensor of Ca2+ levels
Triggers movement of vesicles
Vesicle fuses with membrane
What receptors are present in neuromuscular junctions?
Nicotinic acetylcholine receptors
What kind of channels are receptors?
Ligand-gated channels
What happens after ACh binds to the ACh receptor?
The channel opens
It is permeable to Na+ and K+
What is the Em of the muscle cell?
-90mV
What is the ion movement in the cell?
More Na+ influx than there is K+ efflux
Describe the driving force on Na+ and K+
Na+ is great
K+ is very small
What is the end-plate potential?
-20mV
What determines end-plate potential?
-20mV is the potential after the release of neurotransmitter
What does the end-plate potential initiate?
An action potential in the muscle
What is the difference between the end-plate potential and the action potential?
The end-plate potential decays
Decreases as distance from motor end-plate increases
The action potential does not
What is the delay between a presynaptic action potential and an end-plate potential?
1msec
Comment on the size of an end-plate potential, why?
It is a very large synaptic potential
High density of receptors
Large release of neurotransmitter
