Neuromuscular Junction Flashcards
What is neuromuscular junction?
It is the synapses between motor neurons and skeletal muscles; they are simple, large and easy to see
What are the components you see in NMJ structure?
Presynaptic terminal, vesicles, Schwan cell, basal lamina, muscular fiber, acetylcholine receptors
What is recording endplate potentials (EPP)?
An instrument that evokes action potential in the presynaptic motor neuron to elicit a transient depolarization of the post synaptic muscle.
Who is Eccles, Katz, and Kuffler?
They used tubocurarine to reduce action potential in the frog muscle to be able to record the EPP during acetylcholine release
What is tubocurarine
It is a plant based alkaloid that binds to acetylcholine receptors
What is ionophoresis?
It is the process of applying define amounts of acetylcholine with a brief voltage pulse to the pipette
What is miniature endplate potentials?
It is depolarization on the muscle fiber that is not the huge spike. They are miniature (0.5 mV).
What causes MEPP?
Bernhard Katz found that acetylcholine is released at NMJ in discrete amounts called quanta.
Under low calcium condition, what kind of distribution do EPP’s follow?
Poisson distribution
How many transmitter molecules per quantum?
4000-7000 molecules per quantum
What is a synapse with little integration?
NMJ: 200-300 vesicles
What is synapse with high integration?
Hippocampal synapses: 1-20 vesicles
How many molecules in one vesicle?
10,000 ACh molecules per quanta
Acetylcholine recycling
Acetylcholine esterase cleaves acetylcholine into choline and acetate. Choline is taken up by the presynaptic terminal
