Synaptic Transmission Flashcards
What is a neuromuscular junction?
A synapse between a nerve and skeletal muscle fibre
What are the 3 types of ion channel found in nerve terminals?
Na+, K+ and Ca2+
What opens Ca2+ channels and what does this promote?
- Depolarisation
- Promotes neurotransmitter release
What does Ca2+ bind to in the nerve terminal process?
Synaptotagnin
Which complex makes fusion pores between vesicles and the nerve terminal?
Snare complex
What happens when Ca2+ entry is increased at the nerve terminal?
It increases the frequency of the action potential
Name 3 characteristics of Ca2+ channels in the nerve terminal
- Basis of most cellular processes
- Similar in structure to Na+ channels
- Can activate and inactivate
- Ca2+ channel activation is Ca2+ dependent
Which neurotransmitter and receptor are involved in skeletal muscle contraction?
- Acetylcholine
- Nicotinic ACh receptors
What is an end-plate potential in relation to skeletal muscle?
Cation channel ion movement through nAChR producing depolarisation
What is the name for the process where action potentials initiate contraction of skeletal muscle fibres?
Excitation contraction coupling
What are the 2 types of neuromuscular blockers? Give an example of each
Competitive Blocker - Rocuronium
Depolarising Blocker - Succinylcholine
What is the mechanism of a neuromuscular competitive blocker?
- Binds to AChR instead of ACh
- Can be overcome by increasing ACh concentration
What is the mechanism of a neuromuscular depolarising blocker?
- Binds to nAChR on muscle membrane causing activation
- Maintained depolarisation inactivated Na+ Channels
What is Myasthenia Gravis?
An autoimmune disease targeting nACh receptors
What are the symptoms of Myasthenia Gravis and what causes this?
- Muscle weakness and fatigue
- Receptors are degraded and amplitude of endplate potentials are reduced
How does Organophosphate Poisoning affect Acetylcholinesterase?
Inhibits it by forming a stable irreversible covalent bond to the enzyme
Name 2 differences between nicotinic and muscarinic receptors?
Nicotinic - fast depolarisation through a ligand-gated ion channel
Muscarinic- slow response due to a cascade response via a G-protein
