Neuromuscular junction Flashcards
Is the neuromuscular junction contain alpha or gamma motoneurone?
alpha
The axon terminals are myelinated, true orflase
flase- nerve endings are unmyelinated
where does the presynaptic terminal synapse?
end plate region of skeletal muscle
what kind of ACh receptors are present in the neuromuscular junction
nicotinic in the active zomnes in junctional folds
what is choline transported by?
choline transporter
What is ACh synthesized from and by?
Choline and acetyl CoA choline acetyltrasferase
what is the response to one quantum of transmitter called?
miniature end plate potential
what makes up the end plate potential
all the quantum of miniature end plate potential
How is muscle action brought about involving Ca++, troponin and SR
Action potential arrives at T tubule on sarcoplasmic reticulum causing release of Ca++. This causes contraction by interacting with the troponin associated with the myofibrils
What enzyme breaks down ACh
acetylcholinesterase
What does acetylcholinesterase break acetylcholine down into?
acetate and choline- acetate diffuses from synaptic cleft
What is neuromyotonia
autoimmune where antibodies are produced against voltage activated K channels in motor neurone, causing hyperexcitability.
What are the symptoms of Neuromyotonia
stiffness, slow relaxation, muscle twitches and cramps
How do you treat neuromyotonia
anti-convulsants- carbamazepine, phenytoin
How is lambert eaton myasthenia syndrome determined
muscle weakness in limbs, assoc with small cell carcinoma in the lungs. Antibodies produced against Ca channels, thus decreased Ca entry and reduced ACh
What is the treatment for LEMS
anticholinesterases- pyridostigmine and potassium channel blockers- 3,4- diaminopyridine- increases ACh contraction in synaptic cleft
How would you recognise myasthenia gravis
progressive muscle weakness during periods of activity. Often weakness of the eye presents first
What is the chemistry behind myasthenia gravis?
antibodies produced again nicotinic ACh receptors in end plate, thus decreased EPP
How wouldoyu treat MG
anticholinesterases- edrophonium (increase ACh in cleft) , pyridostigmine for long term treatment and immunosuppressants like azathioprine
What doesBotulinum toxin do?
Irreversibly inhibit ACh release
What gets used to decrease frown lines or wrinkles?
Botulinum toxin!
vecuronium and atracurium drugs are used to treat what? and how do they do this?
reverse muscle paralysis, reduce amplitude of end plate potential to below threshold for muscle fibre action potential to be generated
