11. Nervous Tissue and Nervous System

In unmyelinated axons, action potentials are propagated by_________ conduction.

Dr. Roberts is testing a new drug that blocks sodium channels in the axons of a neuron. Which of the following statements is correct?

Would you expect to find larger motor units in the postural muscles of the back or the muscles of the hand? Explain your answer.

Explain why cardiac muscle cells and some smooth muscle cells will continue to contract even when their nerve supply has been removed

Which of the following statements best describes saltatory conduction?

a. Every section of the axolemma must be depolarized and triggered to generate an action potential.

b. The internodes must generate action potentials.

c. The dendrites and cell bodies propagate EPSPs toward the trigger zone.

d. Only the nodes of Ranvier must generate action potentials.

Identify the following as properties of electrical synapses (ES), chemical synapses (CS), or both (B).           

a. ______The plasma membranes of presynaptic and postsynaptic neurons are joined by gap junctions.          

b. ______Transmission is unidirectional and delayed.          

c. ______A presynaptic neuron and a postsynaptic neuron are involved.          

d. ______The use of neurotransmitters packaged into synaptic vesicles is required.          

e. ______Transmission is nearly instantaneous and bidirectional.