lecture 11 - neuromuscular junctions Flashcards
What is the alternative name for the neuromuscular junction?
Motor end plate
How many neurons innervate a single muscle fibre?
1
How many muscle fibres does a single motor neruon supply?
Usually multiple
What neurotransmitter is used at the neuromuscular junction?
ACh - Acetylcholine
What enzyme is used to break down the neurotransmitter at a neuromuscular junction?
AChE - acetylcholine esterase
What are the sequence of events during a synapse at the neuromuscular junction?
1.) AP in axon
2.) Voltage gated Ca2+ channels open and Ca2+ enters presynaptic cell
3.) Vesicles fuse and release ACh
4.) AcH binds nAChR on muscle fibre
5.) nAChR channel opens and Na+ enters muscle fibre leading to local depolarisation
6.) depolarisation opens more voltage gated Na+ channels
7.) AP propogates down muscle fibre
8.) ACh degraded by AChE
What neurotransmitter receptor is found on the postsynaptic cell of the postsynaptic cell?
nAChR (nicotinic acetylcholine receptor)
What is the life cycle of Acetylcholine at the NMJ?
ACh packaged into vesicles, released into cleft, triggers nACHr, broken down into Choline & Acetic Acid by AChE, transported into neuron by Na+ choline transporter, converted to ACh again
What are the products of ACh breakdown by AChE?
Choline, Acetic Acid
What is AChE?
Acetylcholine esterase - breaks down ACh in the synaptic cleft
What is myasthenia gravis?
An autoimmune condition where nACh receptors are reduced, meaning ACh activation diminished with repetitive activation at the Neuromuscular Junction
How do antibodies impact nAChR in myasthenia gravis?
Reduce receptor number by blocking receptors, damaging the endplate.
What type of medication is used to treat myasthenia gravis, and why?
AChE blockers (anticholinesterases) - they increase the amount of ACh in the neuromuscular junction by decreasing enzyme breakdown, increasing the activation of nAChRs
What is the role of T-tubules in a muscle fibre?
Propagates action potentials into the fibre by going deep in between the myofibrils
What is the name for the cell membrane of a muscle fibre?
Sarcolemma