Control of the neuromuscular junction in this new invertebrate is found to involve dual innervation, where one motor neuron secretes an excitatory neurotransmitter and another secretes an inhibitory neurotransmitter onto the muscle. How does this compare to the human neuromuscular junction? Propose three different types of inhibitory receptors/channels that would produce inhibition of the

Question

invertebrate muscle, specifying ion and direction of ion flow. For each ion, calculate the equilibrium potential. What similarity do you notice in the equilibrium potentials of the ions involved, and how is that significant? How may inhibition be accomplished in human muscle?

What will be an ideal response?

Answer 1

The human neuromuscular junction is innervated by only an excitatory neuron. The inhibitory motor neuron in the
invertebrate may open a channel to potassium, to chloride, or to both, resulting in hyperpolarization as potassium exits and/or chloride enters.
EK+= 61 × log 20/420 = -81 mV. ECl- = -61 × log 550/50 = -64 mV.
Both of these equilibrium potentials are negative, indicating that these ions can be useful for inhibition. In humans,
inhibition of muscle activity occurs within the CNS, rather than at the muscle.