Neuromuscular junction

Question 1

What is the neuromuscular junction?

Answer 1

The synapse between the motor neuron and skeletal muscle

Question 2

How do we trigger muscle contraction?

Answer 2

evoke an action potential in skeletal muscle membrane (the sarcolemma)

Question 3

Describe the neuromuscular junction?

Answer 3

Presynaptic terminal of motor neuron filled with vesicles containing acetylcholine (ACh)- neurotransmitter

Synaptic cleft- gap between motor neuron and muscle cell

Postsynaptic end plate of skeletal muscle fibre

Question 4

Why are there post-junctional folds?

Answer 4

increase no. voltage gated Na+ channels to where end plate potential evoked

Question 4

How do we evoke an action potential in skeletal muscle membrane?

Answer 4

action potential fired in motor neuron and sodium can flood into cell causing depolarisation

depolarisation will lead to opening of voltage gated calcium channels in pre synaptic terminal

calcium pulled into cell by concentration and electrical gradients

Calcium interacts with some synaptic proteins and pulls those vesicles to membrane and causes them to fuse with it (calcium dependent exocytosis)

Acetylcholine will then be released into synaptic cleft and is going to diffuse across it

ACh binds to ACh (nicotinic) receptors

Receptors contain an integral ion channel

Lots of sodium is going to come into muscle cell as being pulled in by conc and electrical gradient

Evokes end plate potential- depolarise membrane to threshold

Voltage gated sodium channels will open and evokes action potential

Propagated along muscle cell membrane

Acetylcholine cleared up by acetylcholinesterase