Motor Units and Neuromuscular Transmission Flashcards
What happens at neuromuscular junctions?
The nerve signals a muscle action potential Myelin sheath is lost boutons terminating junctional folds Vesicle and nicotinic receptor
What happens during neuromuscular transmission?
Impulse arrival opens Ca2+ channels
Exocytosis of clear ACH vesicles into the cleft
Nicotonic ach receptors
Open the cation channels
Small release of NT at rest
Minature end plate potential
arrival of impulse, MEPPs increase in size
Temporal summation, firing level EPP - AP
what is 1 action potential the same as
One twitch (Contraction)
What happens in excitation contraction coupling
APs on sarcolemma Conducted in T tubules voltage gated Ca2+ Coupled with ryanodine receptors on SR release Ca++ intracellular ca2+ pump limits contraction
How is the termination of ACh brought about?
Ach diffuses out of the synaptic cleft
ACh is destroyed by acetylcholinesterase converted to hyrolyse choline and esterase
Ach persists of few miliseconds in synaptic cleft
What can the pharmacological manipulation of NMJ do?
Reduce Ach release
Alter Ach binding
Change activity of ach esterase which increases ach in the body
What is a motor unit
All muscle fibres of same type
One motor neurone and all of the fibres it innervates
What is a fasiculation
a movement of an entire muscle fascicle
What is the size principle
Small motor units activated before larger motor units
