Question

The conduction of action potentials in a myelinated nerve fiber is a. saltatory. b. without decrement. c. faster than in an unmyelinated fiber. d. all of these.

Short answer

The conduction of action potentials in a myelinated nerve fiber is saltatory, without decrement, and faster than in an unmyelinated fiber. Therefore, the correct answer is d. all of these.

Step-by-step solution

Understanding Myelinated Nerve Fibers

Myelinated nerve fibers are nerve cells with a myelin sheath, a protective layer covering the axon. Myelin is composed of lipids and proteins and serves to insulate the axon, speeding up the transmission of action potentials (electrical signals) along the length of the nerve fiber compared to unmyelinated nerve fibers, which lack the myelin coating.

Understanding Saltatory Conduction

Saltatory conduction refers to the "jumping" transmission of action potentials from one node of Ranvier (gaps between myelin sheaths) to the next in myelinated nerve fibers. This "jumping" of action potentials significantly increases the speed of conduction compared to the continuous propagation of action potentials in unmyelinated fibers.

Understanding Decrement

Decrement refers to the decrease in amplitude (strength) of electrical signals as they propagate along a nerve fiber. In myelinated nerve fibers, action potentials are conducted without decrement as they maintain their amplitude (strength) from one node of Ranvier to the next.

Comparing Speed in Myelinated and Unmyelinated Fibers

Action potentials are conducted faster in myelinated nerve fibers compared to unmyelinated fibers, due to saltatory conduction and lack of decrement.

Selecting the Correct Option

Now that we have an understanding of action potentials in myelinated nerve fibers, we can go through each option and evaluate its accuracy: a. Saltatory Conduction - True, as explained in the "Understanding Saltatory Conduction" step. b. Without Decrement - True, as explained in the "Understanding Decrement" step. c. Faster than in an unmyelinated fiber - True, as explained in the "Comparing Speed in Myelinated and Unmyelinated Fibers" step. d. All of these - Since all the previous statements are true, the correct answer is "d. all of these."