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

The Refractory Period

Anatomy & Physiology

11. Nervous Tissue and Nervous System

The Refractory Period

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Problem 8

Textbook Question

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.

Verified step by step guidance

Understand the concept of saltatory conduction: Saltatory conduction is a process in which action potentials 'jump' from one node of Ranvier to the next along a myelinated axon. This occurs because the myelin sheath insulates the axon, preventing ion exchange in the internodal regions and speeding up signal transmission.

Review the structure of a myelinated axon: Myelinated axons have regions covered by myelin (internodes) and small gaps between these regions called nodes of Ranvier. The nodes of Ranvier are the only places where ion exchange (depolarization) occurs during an action potential.

Analyze the role of the nodes of Ranvier: During saltatory conduction, action potentials are generated only at the nodes of Ranvier. The myelin sheath prevents depolarization in the internodes, so the signal 'jumps' from node to node, making conduction faster and more efficient.

Evaluate each answer choice: a) Incorrect, because not every section of the axolemma is depolarized in saltatory conduction; only the nodes of Ranvier are involved. b) Incorrect, because the internodes do not generate action potentials; they are insulated by myelin. c) Incorrect, because this describes the propagation of excitatory postsynaptic potentials (EPSPs) in dendrites and cell bodies, not saltatory conduction. d) Correct, because only the nodes of Ranvier generate action potentials in saltatory conduction.

Conclude that the correct answer is the statement that describes the generation of action potentials only at the nodes of Ranvier, which is option d.

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Key Concepts

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

Saltatory Conduction

Saltatory conduction is a process by which action potentials jump from one node of Ranvier to another along myelinated axons. This mechanism significantly increases the speed of electrical signal transmission in neurons, as the myelin sheath insulates the axon and prevents ion leakage, allowing depolarization to occur only at the nodes.

Nodes of Ranvier

Nodes of Ranvier are small gaps in the myelin sheath of an axon where the axolemma is exposed. These nodes are crucial for saltatory conduction, as they contain a high density of voltage-gated sodium channels, enabling the rapid depolarization necessary for action potentials to occur at these specific points.

Action Potential

An action potential is a rapid, temporary change in the electrical membrane potential of a neuron, allowing for the transmission of signals along the axon. It is initiated when a threshold level of depolarization is reached, leading to the opening of sodium channels and the subsequent influx of sodium ions, which propagates the signal.

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