11. Nervous Tissue and Nervous System

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

c. The Na+/K+ pumps and gated channels maintain the Na+ and K+ gradients necessary for action potentials to occur.

Sequence the following list of events of a neuronal action potential by placing 1 next to the first event, 2 next to the second event, and so on.          

a. ____The activation gates of voltage-gated Na+ channels open, Na+ flood the cytoplasm, and depolarization occurs.          

b. ____K+ continue to flow out of the axon until the membrane is hyperpolarized.          

c. ____Local potentials depolarize the membrane to threshold.          

d. ____The inactivation gates of voltage-gated Na+ channels close as voltage-gated K+ channels open, K+ begin to exit the axon, and repolarization begins.          

e. ____Repolarization continues and Na+ channels return to resting.

The drug neostigmine blocks the actions of acetylcholinesterase in the synaptic cleft. What effect would this have on synaptic transmission? What effects might you expect to see as a result of this drug?

During a surgical procedure, an anesthesiologist administers to the patient an inhaled anesthetic agent that opens Cl− channels in the postsynaptic membranes of neurons in the brain. Explain why this would put the patient 'to sleep' for the duration of the surgical procedure.

Albert accidentally ingests the poison tetrodotoxin from the pufferfish, which you know blocks voltage-gated Na+ channels. Predict the symptoms Albert will experience from this poisoning.

Albert, the patient in question 3, takes the drug lithium, which reduces the permeability of the neuronal axolemma to Na+ (that is, it allows fewer Na+ to enter the axon). Predict the effect this would normally have on his neuronal action potentials. Do you think this drug would be beneficial or harmful, considering his condition?

Predict the effect that tetrodotoxin would have on Albert's muscle fiber action potentials (see question 3). Would it affect end-plate potentials at the motor end plate? Why or why not? (Connects to Chapter 10)

Explain what would happen if depolarization of the trigger zone led to a negative feedback loop instead of a positive one. (Connects to Chapter 1)