Nadya is running an experiment for her neurophysiology class. She incubates neurons with different characteristics in a petri dish with different compounds present, stimulates the initial segment of the axon with an electrode and looks at action potential conduction and neurotransmitter release. In the petri dish, the solution mimics the extracellular fluid.
Her results are summarized in the table above. Assume that a depolarization of 15 mV will reach threshold for all of neurons.
A. List all the experiments where you would expect an action potential to be propagated. Identify in which experiment the action potential
propagation would be the fastest and in which experiment it would be the slowest and explain why.
B. Explain why action potentials wouldn't be propagated in the other experiments.
C. Identify the experiment where you would expect the lowest and highest frequency of action potential generation and why.
D. List all the experiments where you would expect neurotransmitter to be released at the axon terminal and state whether this neurotransmitter release would be normal, increased or decreased. Explain why neurotransmitter would not be released when appropriate.
E. Methylphenidate (also known as Ritalin®) is a medication prescribed to treat ADHD (attention-deficit & hyperactivity disorder) and works as a dopamine reuptake inhibitor. Knowing that dopamine is an excitatory neurotransmitter, what effects would this drug have on action potential generation in the post-synaptic neuron and why.