Multiple Choice
Which of the following best describes the primary difference between memory T cells and cytotoxic T cells?
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10. Cell Signaling
Introduction to Cell Signaling
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Which of the following best characterizes depolarization in a cell membrane?
A
An efflux of K\(^+\) ions causing the membrane potential to become more negative
B
The restoration of the resting membrane potential after an action potential
C
A rapid influx of Na\(^+\) ions causing the membrane potential to become less negative
D
The movement of Cl\(^-\) ions into the cell making the inside more negative
Verified step by step guidance1
Step 1: Understand the concept of depolarization. Depolarization refers to the process by which the membrane potential of a cell becomes less negative (closer to zero) compared to its resting state. This is a key event in the generation of an action potential in excitable cells like neurons and muscle cells.
Step 2: Recall the role of ions in membrane potential. The resting membrane potential is typically negative due to the distribution of ions across the membrane. Sodium (Na\(^+\)), potassium (K\(^+\)), chloride (Cl\(^-\)), and other ions play critical roles in maintaining and altering this potential.
Step 3: Analyze the options provided. Depolarization is characterized by a rapid influx of Na\(^+\) ions into the cell, which reduces the negativity of the membrane potential. This is distinct from processes like the efflux of K\(^+\) ions (which typically occurs during repolarization) or the movement of Cl\(^-\) ions (which would make the membrane potential more negative).
Step 4: Relate depolarization to the action potential. During an action potential, depolarization is the initial phase where voltage-gated Na\(^+\) channels open, allowing Na\(^+\) ions to rush into the cell. This influx causes the membrane potential to become less negative and may even become positive.
Step 5: Confirm the correct characterization. Based on the explanation, the best characterization of depolarization is 'A rapid influx of Na\(^+\) ions causing the membrane potential to become less negative.' This aligns with the physiological process observed during the initiation of an action potential.
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