11. Nervous Tissue and Nervous System

The anatomical region of a multipolar neuron where the AP is initiated is the

a. Soma

b. Dendrites

c. Axon's initial segment

d. Axon terminals

Since all APs generated by a given nerve fiber have the same magnitude, how does the CNS 'know' whether a stimulus is strong or weak?

What is the polarized membrane state? How is it maintained? (Note the relative roles of both passive and active mechanisms.)

Describe the events that must occur to generate an AP. Relate the sequence of changes in permeability to changes in the ion channels, and explain why the AP is an all-or-none phenomenon.

When admitted to the emergency room, Sean was holding his right hand, which had a deep puncture hole in its palm. He explained that he had fallen on a nail while exploring a barn. Sean was given an antitetanus shot to prevent neural complications. Tetanus bacteria fester in deep, dark wounds, but how do their toxins travel in neural tissue?

Local anesthetics block voltage-gated Na⁺ channels. General anesthetics are thought to activate chemically gated Cl⁻ channels, thereby rendering the nervous system quiescent while surgery is performed. What specific process do anesthetics impair, and how does this interfere with nerve impulse transmission?

Rochelle developed multiple sclerosis when she was 27. After eight years she had lost a good portion of her ability to control her skeletal muscles. How did this happen?

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

A depolarization is a change in membrane potential that makes the potential less negative.

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

A local potential is a change in membrane potential that conducts the long-distance signals of the nervous system.

A drug that blocks Na⁺ channels in neurons does so not only in the axon but also in the dendrites and cell body. What overall effect would this have on action potential generation?

What would happen if the drug blocked K⁺ channels instead?

Describe the steps involved in the generation of an action potential.