14. The Autonomic Nervous System

The effects of neurotransmitter binding are very brief. Explain.

Inhibition of acetylcholinesterase by poisoning blocks neurotransmission at the neuromuscular junction because

a. ACh is no longer released by the presynaptic terminal.

b. ACh synthesis in the presynaptic terminal is blocked.

c. ACh is not degraded, so prolonged depolarization is enforced on the postsynaptic cell.

d. ACh is blocked from attaching to the postsynaptic ACh receptors.

What are the two types of receptors found in the parasympathetic system?

The poison curare (kyoo-RAH-ray) blocks the binding of acetylcholine to its receptors at the neuromuscular junction. What effects would you predict from such a poison? Can you think of any useful applications for it? Why might an overdose of it be lethal?

In the Netherlands a young man named Jan was admitted to the emergency room. He and his friends had been to a rave. His friends say he started twitching and having muscle spasms which progressed until he was 'stiff as a board.' On examination, staff found a marked increase in muscle tone and hyperreflexia involving facial and limb muscles. In his pocket, he had unmarked dark yellow tablets with dark flecks. Analysis of the tablets showed them to contain a mixture of ecstasy and strychnine. Ecstasy would not cause this clinical picture, but strychnine, which blocks glycine receptors, could. Explain how.

The neurotransmitter released at all synapses in the parasympathetic division is:

The drug neostigmine blocks the activity of the enzyme acetylcholinesterase in the synaptic cleft. Predict the effects of this drug.

___________ and ___________ are the major neurotransmitters released by autonomic nervous system neurons.

Since at any moment a neuron is likely to have thousands of neurons releasing neurotransmitters at its surface, how is neuronal activity (to fire or not to fire) determined?