the neuromuscular junction Flashcards
what does nerve signal trigger?
triggers muscle action potential
how does the neuromuscular interaction work?
delivered by one motor neuron
if a neuron is triggered how many fibres are triggered
1+ at the same time
what is a neuronal ending to a muscle fibre
neuromuscular junction
what do synaptic end bulbs do?
release neurotransmitter
how many steps is there at neuromuscular junction
4
what are the 4 steps in neuromuscular junction
-Release of the neurotransmitter, acetylcholine (ACh)
Diffuses across cleft
-Activation of ACh receptors on sarcolemma
-Generation of Muscle Action Potential
Repeats with each nerve action potential
-Breakdown of ACh by the enzyme acetylcholinesterase
what happens when a muscle initiates a contraction
Muscle action potential
Ca2+ released from the Sarcoplasmic
Reticulum (SR)
4 Ca2+ bind to troponin
Moves tropomyosin off actin sites
Myosin binds to actin and starts the contraction cycle
what does myosin bind to in the contraction cycle
what does it release
binding to actin
releases phosphate group
(forming cross-bridge)
what does the cross-bridge release in contraction cycle
ADP & shortening sarcomere (power stroke)
what does ATP bind to in and then release contracting cycle
binds to myosin
release of myosin from actin
if ATP is broken down to ADP & Pi what does it activate
myosin head to bind and start again
when the muscle is relaxing what happens
A breakdown of ACh happens
stops muscle action potentials by acetylcholinesterase
where do the Ca2+ ions go in relaxation in the muscles
transported back into SR lowering concentration
what happens when the nerves are cut in the muscle
fibres become flaccid
very limp
