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. Understand the concept of an action potential: An action potential is a rapid rise and subsequent fall in voltage or membrane potential across a cellular membrane, typically observed in neurons.
2. Identify the key feature of action potentials: Action potentials are initiated when a depolarization event reaches a certain threshold level, causing voltage-gated ion channels to open.
3. Clarify the term 'threshold': The threshold is the critical level to which a membrane potential must be depolarized to initiate an action potential. This is a specific voltage value that triggers the opening of sodium channels.
4. Examine the options given: Analyze each option to determine which one accurately describes the initiation of an action potential. Focus on the role of depolarization reaching the threshold.
5. Conclude with the correct feature: Recognize that the correct answer is the option that describes action potentials being triggered by a depolarization that reaches threshold, as this is a fundamental characteristic of how action potentials are initiated.

Key Concepts

Action Potential

An action potential is a rapid rise and subsequent fall in voltage or membrane potential across a cellular membrane, primarily in neurons. It is initiated when a neuron receives a stimulus that causes depolarization to reach a threshold, leading to a sequence of ionic exchanges across the membrane. This process is essential for nerve signal transmission.

Depolarization and Threshold

Depolarization refers to the reduction in membrane potential, making the inside of the neuron less negative compared to the outside. When depolarization reaches a specific threshold, it triggers an action potential. This threshold is crucial as it determines whether the neuron will fire an action potential, thus playing a key role in neural communication.

Propagation of Action Potentials

Action potentials propagate along axons at varying speeds, influenced by factors such as axon diameter and myelination. Larger diameter axons and those with myelin sheaths conduct impulses faster due to reduced resistance and saltatory conduction. Understanding this variability is important for comprehending how signals are transmitted efficiently in the nervous system.