Action Potentials Crossword Answer Key


Action potentials are crucial for the transmission of electrical signals in the nervous system. These rapid changes in voltage allow neurons to communicate with each other and facilitate various physiological processes. Understanding the intricacies of action potentials is essential for comprehending the functioning of the nervous system. In this article, we will explore the action potentials crossword answer key, providing a comprehensive analysis of the different components and mechanisms involved.

1. The Neuron and Resting Potential

To understand action potentials, it is important to first grasp the basics of neuron structure and function. Neurons are specialized cells responsible for transmitting information throughout the body. At rest, neurons maintain a negative charge inside the cell compared to the outside, known as the resting potential. This resting potential is maintained by the selective permeability of the neuron’s cell membrane to ions such as potassium (K+) and sodium (Na+).

2. Depolarization and Threshold

When a neuron receives a stimulus, it can initiate an action potential. This process begins with depolarization, where the voltage across the cell membrane becomes less negative. If the depolarization reaches a certain threshold, typically around -55 millivolts (mV), an action potential is triggered. The threshold is a critical point that ensures only strong enough signals are transmitted, preventing weak or irrelevant stimuli from activating the neuron.

3. Rising Phase and Falling Phase

Once the threshold is reached, the neuron undergoes a series of rapid changes in voltage during the action potential. The rising phase is characterized by a sudden influx of sodium ions into the neuron, causing a rapid increase in voltage. This influx occurs through voltage-gated sodium channels that open in response to depolarization. As the voltage reaches its peak, typically around +40 mV, these sodium channels close, initiating the falling phase.

During the falling phase, the neuron undergoes repolarization, where the voltage returns to its resting potential. This process involves the opening of voltage-gated potassium channels, allowing potassium ions to flow out of the neuron. The efflux of potassium ions restores the negative charge inside the cell, bringing the voltage back to its resting potential.

4. Refractory Period and Propagation

Following an action potential, the neuron enters a refractory period, during which it is temporarily unable to generate another action potential. This period allows the neuron to reset and ensures that action potentials propagate in one direction, preventing backward transmission. The refractory period is divided into two phases: the absolute refractory period, where no action potential can be generated, and the relative refractory period, where a stronger stimulus is required to initiate an action potential.

Action potentials also propagate along the neuron’s axon, allowing signals to travel long distances. This propagation occurs through a process called saltatory conduction in myelinated neurons. The myelin sheath, formed by glial cells, insulates the axon and increases the speed of signal transmission. Action potentials “jump” from one node of Ranvier to another, skipping the myelinated regions and speeding up the overall transmission.


Action potentials are fundamental for neuronal communication and the functioning of the nervous system. Understanding their mechanisms and components is crucial for comprehending how information is transmitted within our bodies. In this article, we explored the action potentials crossword answer key, delving into topics such as resting potential, depolarization, threshold, rising and falling phases, refractory periods, and propagation. By gaining a deeper understanding of action potentials, we can appreciate the complexity and efficiency of our nervous system’s communication network.

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