11. Nervous Tissue and Nervous System

Which of the following electrical events occurs when a certain threshold is reached?

Which of the following is characteristic of an action potential?

An action potential is a phenomenon that either happens completely or doesn't happen at all.

Which part of the action potential occurs when the voltage-gated Na⁺ channels are inactivating and voltage-gated K⁺ channels open?

The CNS can discriminate between strong and weak stimuli as strong stimuli __________.

During which phase of an action potential are voltage-gated K⁺ channels open, while voltage-gated Na⁺ channels are closed?

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