Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

11. Nervous Tissue and Nervous System

Propagation of Action Potentials

Anatomy & Physiology

11. Nervous Tissue and Nervous System

Propagation of Action Potentials

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2:08 minutes

Problem 14

Textbook Question

The velocity of nerve impulse conduction is greatest in
a. Heavily myelinated, large-diameter fibers
b. Myelinated, small-diameter fibers
c. Nonmyelinated, small-diameter fibers
d. Nonmyelinated, large-diameter fibers

Verified step by step guidance

Understand the role of myelination: Myelin is a fatty sheath that insulates axons, allowing electrical impulses to travel faster by enabling saltatory conduction, where the impulse jumps between nodes of Ranvier.

Consider the effect of fiber diameter: Larger-diameter fibers have less resistance to the flow of ions, which facilitates faster conduction of nerve impulses compared to smaller-diameter fibers.

Compare the options: Heavily myelinated fibers will conduct impulses faster than nonmyelinated fibers due to the presence of myelin. Similarly, large-diameter fibers will conduct faster than small-diameter fibers due to reduced resistance.

Eliminate incorrect options: Nonmyelinated fibers (options c and d) will have slower conduction velocities compared to myelinated fibers. Among myelinated fibers, small-diameter fibers (option b) will conduct slower than large-diameter fibers.

Conclude based on the analysis: The combination of heavy myelination and large diameter (option a) results in the greatest velocity of nerve impulse conduction.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Myelination

Myelination refers to the process of forming a myelin sheath around the axons of neurons. This sheath, composed of lipid-rich layers, acts as an insulator, allowing electrical impulses to travel more quickly along the nerve fibers. Heavily myelinated fibers exhibit faster conduction velocities due to reduced ion leakage and increased efficiency in signal transmission.

Axon Diameter

The diameter of an axon significantly influences the speed of nerve impulse conduction. Larger-diameter axons provide less resistance to the flow of ions, facilitating faster transmission of action potentials. This is particularly important in the context of myelinated fibers, where the combination of large diameter and myelination maximizes conduction velocity.

Saltatory Conduction

Saltatory conduction is the process by which nerve impulses jump from one node of Ranvier to another along myelinated axons. This mechanism greatly enhances the speed of conduction compared to continuous conduction in nonmyelinated fibers. The presence of myelin allows for rapid depolarization at the nodes, making it a key factor in the efficiency of nerve signal transmission.

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