Chapter 35, Problem 3STP

Summary Introduction

Introduction:

Neurons are specialized cells that allow us to gather information about our world. Neurons make up an immense network of communication in our body called the nervous system. The nerve impulse is an electrical charge that travels the length of a neuron. An impulse is the product of a stimulus, like a touch or a loud bang that causes us to jump.

Answer to Problem 3STP

Correct answer:

The correct answer is option (C) Sodium ions move into the nerve cell.

Explanation of Solution

Explanation/justification for the correct answer:

Option (C) Sodium ions move into the nerve cell. The minimum stimulus to give rise to the potential for action is a threshold. Stronger stimulus does not generate a stronger potential for action. The channels in the plasma membrane open when the stimulus reaches the threshold. Sodium ions move quickly through these channels into the cytoplasm of the neurons, causing a temporary reversal of electrical charges. So, the correct answer is option (C).

Explanation for incorrect answer:

Option (A) Potassium channels in the cell membrane open. Since sodium ions pass through the nerve cell, the inner side of the cell has a positive charge, which allows other channels to open up. Potassium ions exit the cell through these pathways, creating a positive charge outside the cell. So, this is an incorrect answer.

Option (B) Neurotransmitters are released into the synapse. In a nerve cell, the channels in the plasma membrane open when the stimulus crosses the threshold. Sodium ions pass rapidly through these channels through the cytoplasm of the neurons, causing a temporary reversal of electrical charges. So, this is an incorrect answer.

Option (D) The cell becomes negatively charged. Since sodium ions pass through the nerve cell, the inner side of the cell has a positive charge, which allows other channels to open up. Potassium ions exit the cell through these pathways, creating a positive charge outside the cell. So, this is an incorrect option.