A common feature of action potentials is that they a. cause the membrane to hyperpolarize and then depolarize. b. can undergo temporal and spatial summation. c. are triggered by a depolarization that reaches threshold. d. move at the same speed along all axons.

Verified step by step guidance

1. Step 1: Understand the concept of action potentials. Action potentials are rapid, temporary changes in a neuron's membrane potential. They are the fundamental units of communication in the nervous system.
2. Step 2: Evaluate each option individually. Option a suggests that action potentials cause the membrane to hyperpolarize and then depolarize. This is partially correct. During an action potential, the membrane first depolarizes, then repolarizes, and may hyperpolarize briefly before returning to the resting state.
3. Step 3: Consider option b, which states that action potentials can undergo temporal and spatial summation. This is incorrect. Summation refers to the additive effect of multiple postsynaptic potentials, not action potentials.
4. Step 4: Look at option c, which says that action potentials are triggered by a depolarization that reaches threshold. This is correct. When the membrane potential reaches a certain threshold, voltage-gated sodium channels open, leading to a rapid influx of sodium ions and the initiation of an action potential.
5. Step 5: Finally, consider option d, which suggests that action potentials move at the same speed along all axons. This is incorrect. The speed of action potential propagation can vary depending on factors such as axon diameter and the presence of myelination.

Key Concepts

Action Potential

An action potential is a rapid, temporary change in the membrane potential of a neuron, characterized by depolarization followed by repolarization. It occurs when a neuron's membrane potential reaches a certain threshold, leading to the opening of voltage-gated ion channels. This process allows sodium ions to flow into the cell, causing depolarization, followed by potassium ions exiting the cell to restore the resting potential.

Threshold Potential

Threshold potential is the critical level to which a membrane potential must be depolarized to initiate an action potential. If the depolarization reaches this threshold, it triggers a cascade of events that lead to the opening of additional ion channels, resulting in a full action potential. This concept is essential for understanding how neurons communicate and transmit signals.

Propagation of Action Potentials

The propagation of action potentials refers to the way these electrical signals travel along the axon of a neuron. This process can vary in speed depending on factors such as axon diameter and myelination. Myelinated axons conduct action potentials faster due to saltatory conduction, where the action potential jumps between nodes of Ranvier, while unmyelinated axons conduct more slowly.