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.