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Ch. 25 Fluid, Electrolyte, and Acid-Base Homeostasis
Amerman- Human Anatomy & Physiology 3e
Amerman3rd EditionHuman Anatomy & PhysiologyISBN: 9780138247201, 9780138247928, 9780138201814Not the one you use?Change textbook
All textbooksAmerman 3rd EditionCh. 25 Fluid, Electrolyte, and Acid-Base HomeostasisProblem 10a
Chapter 25, Problem 10a

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.
a. Potassium ions are responsible for the repolarization phase of the action potential.

Verified step by step guidance
1
Understand the context: The problem is about the phases of an action potential, which is a rapid change in membrane potential in excitable cells like neurons and muscle cells. The repolarization phase specifically involves the return of the membrane potential to its resting state after depolarization.
Recall the role of ions in the action potential: During the depolarization phase, sodium (Na⁺) ions rush into the cell, making the inside more positive. During the repolarization phase, potassium (K⁺) ions move out of the cell, restoring the negative membrane potential.
Evaluate the statement: The statement claims that potassium ions are responsible for the repolarization phase. Based on the physiology of action potentials, this is correct because the efflux of K⁺ ions through voltage-gated potassium channels is the primary mechanism for repolarization.
Determine if the statement is true or false: Since potassium ions are indeed responsible for the repolarization phase, the statement is true.
If the statement were false, correct it: For educational purposes, if the statement had been false (e.g., if it incorrectly stated that sodium ions are responsible for repolarization), the correction would be: 'Potassium ions, not sodium ions, are responsible for the repolarization phase of the action potential.'

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Key Concepts

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

Action Potential

An action potential is a rapid change in the electrical membrane potential of a neuron or muscle cell, which occurs when a stimulus causes the cell to depolarize. This process involves the influx of sodium ions (Na+) followed by the efflux of potassium ions (K+), leading to a brief reversal of the membrane potential. Understanding the phases of an action potential is crucial for analyzing neuronal signaling.
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Action Potential

Repolarization Phase

The repolarization phase of an action potential occurs after depolarization, where the membrane potential returns to a more negative value. This phase is primarily driven by the efflux of potassium ions (K+) through voltage-gated potassium channels, which helps restore the resting membrane potential. Recognizing the role of potassium ions in this phase is essential for understanding neuronal excitability.
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Ionic Movement in Neurons

Ionic movement in neurons refers to the flow of ions across the cell membrane, which is critical for generating and propagating action potentials. Sodium (Na+) and potassium (K+) ions play key roles in this process, with Na+ influx causing depolarization and K+ efflux leading to repolarization. A clear grasp of ionic movement is necessary to accurately assess the statements regarding action potentials.
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Related Practice
Textbook Question

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

d. Hypocalcemia causes neurons to become hyperexcitable, leading to potential tetanic contractions.

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Textbook Question

Which of the following effects tend to be caused by hypernatremia?

a. Inhibition of ADH secretion

b. Cellular crenation

c. Cellular swelling

d. Increased urine production

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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.

c. Hyperkalemia tends to decrease the resting membrane potential and hyperpolarize excitable cells.

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Textbook Question

Which of the following statements best describes the principle of mass balance?

a. The amount of a variable that is gained by the body through ingestion equals the amount that is lost from the body.

b. The body maintains a stable mass at all times.

c. The amount of each variable brought into the body must be balanced by all other variables.

d. The amount of a variable ingested is regulated by a positive feedback loop.

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Textbook Question

Which of the following is false with respect to sodium ions in human physiology?

a. Sodium ions are the most abundant extracellular cation.

b. Sodium ions are an important osmotic particle in the ECF.

c. The entry of sodium ions into a cell causes depolarization.

d. Sodium ions are more concentrated in the cytosol than in the ECF.

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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.

b. Insulin, aldosterone, and epinephrine stimulate the uptake of potassium ions into cells.

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