Neuromuscular juntion Q

[physionerd]

Hi! Im new to the forums and i need your help regarding neuromuscular synapse.

If a nerve electrical response is 100%, is the muscle electrical and mechanical response at max too? Please explain.

Thank you :)

[Dr. X]

my weakest subject physio.. so in the process of learning to love a hate subject. i'll give it a shot. would love a good discussion.

short answer, no. for example, lets take a muscarinic junction (working with motor end plate and ach). from the presynaptic cell, the action potential relays its response to presynapitc terminal. im not sure about what 100% is, so lets jus say a high impulse is flowin down causing an action potential on the presynaptic terminal. That would cause the ca++ uptake, which in turn releases the Ach into the synaptic cleft from the vesicles. Almost everyone is familiar with the diagram i hope.

Ach receptors on the muscle is also a Na+, K+ channel, so the binding of Ach to it would cause the action potential, ie depolarization and the response. There can be several reasons how the ach receptors could be blocked, for example botulinus toxin or any sort of antimuscarinic blocking agents (drug). These could have a potential effect on the muscle's response.

Without any abnormalities in the synaptic cleft, the high impulse from the nerve should have no problem attaining the threshold potential on the muscle end. Also if there's an electrolyte disturbances (hypo/hyperkalemia --> muscle weakness), that might change the muscle's response potential. im not sure if anyone wants me to get into how K+ abnor. causes weakness.

[Dr. X]

did anyone catch that i said 'antimuscarinic blocking' agent. double negative. i meant antimuscarinic agent.