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Ch. 11 Introduction to the Nervous System and Nervous Tissue
Amerman - Human Anatomy & Physiology 2nd Edition
Amerman2nd EditionHuman Anatomy & PhysiologyISBN: 9780136873822Not the one you use?Change textbook
All textbooksAmerman 2nd EditionCh. 11 Introduction to the Nervous System and Nervous TissueProblem 8
Chapter 11, Problem 8

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
1
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.
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Types of Propagation: Saltatory Conduction

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.
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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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Related Practice
Textbook Question

Which of the following is not a method by which the effects of neurotransmitters are terminated?

a. Reuptake into the presynaptic neuron

b. Diffusion away from the synaptic cleft and uptake by glial cells

c. Movement back to the cell body by retrograde axonal transport

d. Degradation by enzymes in the synaptic cleft

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Textbook Question

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.

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Textbook Question

The ________ is the period of time during which it is impossible to stimulate a neuron to have an action potential, whereas the ________ is the period of time during which a larger-than-normal stimulus is required to elicit an action potential.

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Textbook Question

Describe the three components of the neuromuscular junction.

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Textbook Question

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

A depolarization is a change in membrane potential that makes the potential less negative.

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Textbook Question

The trigger for exocytosis of synaptic vesicles from the presynaptic neuron is:

a. Arrival of an action potential at the axon terminal and influx of calcium ions.

b. Summation of IPSPs at the presynaptic neuron.

c. Binding of neurotransmitters to the axon hillock.

d. Influx of Na+ into the postsynaptic neuron.

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