Question

Which of the amino acids neurotransmitters would be responsible for producing an action potential and which would most likely be released to prevent an action potential from occurring? Can you think of a time when it might be helpful to have a neurotransmitter that, when it binds to the post-synaptic cell, it inhibits an action potential?

Answer 1

Neurotransmitters are of 2 types: excitatory and inhibitory. Means excitatory neurotransmitters generate action potential in the neurons while inhibitory neurotransmitter inhibits action potential. Excitatory neurotransmitters are dopamine and acetylcholine and inhibitory are GABA(Gamma amino butyric acid), dopamine also but in different way.

A neurotransmitter that opens a sodium channel in the postsynaptic cell, would move the membrane potential of that cell in a positive direction i.e. Na ion has positive charge and thus would be an excitatory neurotransmitter. A neurotransmitter that opens a Cl^- channel would move the membrane potential of the cell in a negative direction so is inhibits action potential.

The open channels are selectively permeable to chloride or potassium ions(depending on the type of receptor) and allow these ions to pass through the membrane. If the electrochemical potential of the ion is more negative than that of the action potential threshold then the resultant conductance change that occurs due to the binding of GABA to its receptors keeps the postsynaptic potential more negative than the threshold and decrease the probability of postsynaptic neuron completing an action potential.