Question

Which of these is not a characteristic of action potentials? a. They are produced by voltage-regulated gates. b. They are conducted without decrement. c. \(\mathrm{Na}^{+}\)and \(\mathrm{K}^{+}\)gates open at the same time.

Short answer

Option c stating 'Na+ and K+ gates open at the same time' is not a characteristic of action potentials, as Na+ gates open first, causing depolarization, while K+ gates open later, resulting in repolarization.

Step-by-step solution

Recall the characteristics of action potentials

Action potentials are produced by voltage-gated ion channels that help in the flow of sodium (Na+) and potassium (K+) ions across the cell membrane. They are characterized by the following steps: 1. Resting state: The neuron is at the resting membrane potential, and all voltage-gated channels are closed. 2. Depolarization: Voltage-gated Na+ channels open, allowing Na+ ions to flow into the neuron, making the membrane potential more positive. 3. Repolarization: Voltage-gated K+ channels open, inducing a flow of K+ ions out of the neuron, making the membrane potential more negative again. 4. Hyperpolarization: More K+ ions flow out of the neuron, making the membrane potential even more negative. 5. Refractory period: The neuron returns to its resting membrane potential. Now, let's examine each of the given options:

Option a: They are produced by voltage-regulated gates

Voltage-regulated gates refer to the voltage-gated ion channels responsible for the flow of Na+ and K+ ions during the action potential. This statement is a characteristic of action potentials.

Option b: They are conducted without decrement

This statement means that action potentials don't lose their strength as they propagate along the neuron. This characteristic is true for action potentials due to their all-or-nothing nature, ensuring the signal's strength is maintained.

Option c: Na+ and K+ gates open at the same time

During an action potential, the opening of Na+ and K+ gates occurs at different times. Na+ gates open first, causing depolarization, while K+ gates open later, resulting in repolarization. So, this statement is incorrect and is not a characteristic of action potentials.

Option d: The membrane potential reverses polarity during depolarization

When an action potential is initiated, the membrane potential depolarizes, meaning it becomes less negative or more positive, as Na+ ions flow into the neuron. This process involves polarity reversal and is a characteristic of action potentials.

Conclusion

From the analysis above, option c stating 'Na+ and K+ gates open at the same time' is not a characteristic of action potentials and is the correct answer to the given question.