Synaptic Transmission And Neuromuscular Junction (session 5) Flashcards
How is a signal passed from nerve to muscle?
Neuromuscular junction (synapse between nerve and skeletal muscle fibre)
Which voltage-gated channels are present in the nerve terminal?
Na+
K+
Ca2+
What happens at the nerve terminal? (4)
- Depolarisation
- Opens voltage-gated Ca2+ channels
- Ca2+ entry
- Release of neurotransmitter
Why can the internal concentration of Ca2+ be increased significantly at the nerve terminal?
Because the concentration of Ca2+ inside is so low
Complete the sentence:
Increasing the frequency of AP _________ the amount of nerve terminal Ca2+ entry
Increases
The alpha subunit of voltage-gated Ca2+ channels is very similar to which other voltage-gated channel?
Na+
What is a pore forming subunit necessary for?
A functional channel
What do other associated subunits do in channels?
Fine-tune the properties and enable correct regulation of channel activity
True or false: voltage-gated Ca2+ channels activate quicker than voltage-gated Na+ channels
FALSE
What does acetylcholine esterase do?
Breaks down ACh
What type of acetylcholine receptors are on the postsynaptic membrane?
Nicotinic
Describe the process of transmitter release (5)
- Ca2+ entry through Ca2+ channels
- Ca2+ binds to synaptotagmin
- Vesicle brought close to membrane
- Snare complex make fusion pore
- Transmitter released through this pore
What is reverse potential?
No net flow of charge when the channel is open-halfway between K+ and Na+ equilibrium potential
What happens at the synaptic cleft when two ACh molecules bind to the receptor?
Leads to a conformational change and the pore opens
What is excitation contraction coupling?
Muscle AP initiated adjacent to the end-plate and propagates along the muscle fibre.
The AP initiates contraction of the skeletal muscle fibre.