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Ch. 11 Fundamentals of the Nervous System and Nervous Tissue
Marieb - Human Anatomy & Physiology 11th Edition
Marieb, Hoehn11th EditionHuman Anatomy & PhysiologyISBN: 9780136874034Not the one you use?Change textbook
All textbooksMarieb, Hoehn 11th EditionCh. 11 Fundamentals of the Nervous System and Nervous TissueProblem 18
Chapter 11, Problem 18

What is the polarized membrane state? How is it maintained? (Note the relative roles of both passive and active mechanisms.)

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Understand that the polarized membrane state refers to the difference in electrical charge across the plasma membrane of a cell, typically a neuron or muscle cell, where the inside of the cell is more negative relative to the outside.
Recognize that this polarization is primarily due to the unequal distribution of ions, especially sodium (Na\^+), potassium (K\^+), chloride (Cl\^-), and negatively charged proteins, across the membrane.
Identify the passive mechanisms that contribute to maintaining polarization, such as the selective permeability of the membrane to ions (mainly K\^+ leaking out of the cell) and the diffusion of ions down their concentration gradients through ion channels.
Explain the active mechanism, which is the sodium-potassium pump (Na\^+/K\^+ ATPase), that uses ATP energy to actively transport 3 Na\^+ ions out of the cell and 2 K\^+ ions into the cell, against their concentration gradients, helping to maintain the resting membrane potential.
Summarize that the polarized state is maintained by a balance between passive ion movement (diffusion and leakage) and active transport (Na\^+/K\^+ pump), which together establish and preserve the resting membrane potential essential for cell excitability.

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Key Concepts

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

Polarized Membrane State

The polarized membrane state refers to the difference in electrical charge across a cell's plasma membrane, typically with the inside being more negative relative to the outside. This resting membrane potential is essential for functions like nerve impulse transmission and muscle contraction.
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Characteristic 1: Polarity

Passive Mechanisms in Membrane Polarization

Passive mechanisms involve the movement of ions down their electrochemical gradients through ion channels, such as potassium ions leaking out of the cell. These movements help establish and maintain the resting membrane potential without energy expenditure.
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Passive vs. Active Transport

Active Mechanisms in Membrane Polarization

Active mechanisms use energy, primarily from ATP, to transport ions against their concentration gradients via pumps like the sodium-potassium ATPase. This pump moves sodium out and potassium into the cell, crucially maintaining ion gradients that sustain the polarized state.
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Active Transport
Related Practice
Textbook Question

Local anesthetics block voltage-gated Na⁺ channels. General anesthetics are thought to activate chemically gated Cl⁻ channels, thereby rendering the nervous system quiescent while surgery is performed. What specific process do anesthetics impair, and how does this interfere with nerve impulse transmission?

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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

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Textbook Question

When admitted to the emergency room, Sean was holding his right hand, which had a deep puncture hole in its palm. He explained that he had fallen on a nail while exploring a barn. Sean was given an antitetanus shot to prevent neural complications. Tetanus bacteria fester in deep, dark wounds, but how do their toxins travel in neural tissue?

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Textbook Question

a. Describe the composition and function of the cell body.

b. How are axons and dendrites alike? In what ways (structurally and functionally) do they differ?

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Textbook Question

The effects of neurotransmitter binding are very brief. Explain.

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Textbook Question

a. Contrast unipolar, bipolar, and multipolar neurons structurally.

b. Indicate where each is most likely to be found.

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