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

Neuropeptides that act as natural opiates include

a. Substance P

b. Somatostatin and cholecystokinin

c. Tachykinins

d. Enkephalins

Receptors that bind acetylcholine at the postsynaptic membrane are:

(a) Chemically gated channels

(b) Voltage-gated channels

(c) Passive channels

(d) Mechanically gated channels

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?

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 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?

Match the following neurotransmitters with their correct description.    

_____ GABA    

_____ Dopamine     

_____ Substance P     

_____ Acetylcholine    

_____ Glutamate     

_____ Endorphins     

_____ Norepinephrine

a. Neuropeptide involved in transmission of pain

b. Neurotransmitter released at the neuromuscular junction

c. Major excitatory neurotransmitter in the brain

d. Major inhibitory neurotransmitter in the brain

e. Neuropeptide involved in relief of pain

f. Catecholamine involved in the autonomic nervous system

g. Catecholamine involved in movement and behavior

Which neurotransmitter(s) is/are used by sympathetic postganglionic neurons?

a. Epinephrine

b. Norepinephrine

c. Acetylcholine

d. Both a and b

e. All of the above

Many chemical warfare agents, such as the poisonous gas sarin, block the enzyme acetylcholinesterase in the synaptic cleft. What effects will this poison have on muscle contraction? What effects will it have on the autonomic nervous system? What symptoms would you expect to see from this poison?