An action potential is the electrical signal that travels down an axon when a neuron receives a sufficiently strong stimulus. This impulse operates on an all-or-none principle, meaning it either fires completely or not at all. The propagation of the signal involves the movement of sodium (Na+) and potassium (K+) ions across the neuronal membrane.

Action Potential

Between signals, a neuron's membrane potential is maintained in a state of readiness known as the resting potential. In this condition, ions—such as sodium (Na+) and potassium (K+)—accumulate closely on either side of the cell membrane. This separation of charges acts much like a stretched rubber band storing potential energy, leaving the ions prepared to rush across the membrane as soon as the neuron activates and its gates open.

Resting Potential

The membrane potential is the difference in electrical charge between the intracellular and extracellular fluids across the neuronal membrane. This electrical difference serves as the energy source for the neural signal.

Membrane Potential

The threshold of excitation represents the critical level of membrane potential that a neuron must reach to initiate an action potential. This specific charge level (approximately -55mV) is attained when an influx of positive ions enters the cell, making the internal environment sufficiently positive. Once this exact threshold is surpassed, the neuron becomes active and inevitably triggers an action potential.

Threshold of Excitation

When two neurons repeatedly become stimulated, the signal transmission between them gets enhanced. This enhancement is known as long-term potentiation (LTP). 

Long-term Potentiation (LTP)

The process of neuronal communication is described as an electrochemical event because it involves two distinct stages. The electrical stage is the movement of the action potential down the axon, while the chemical stage is the transmission of the signal across the synaptic space via neurotransmitters.

Neuronal Communication as an Electrochemical Event

Based on the patient's medication described in the case study, explain how the normal process of communication between two neurons is interrupted, leading to reduced neural activity.

Pharmacological Intervention in Neural Pathways

It is important to understand how electrical signals move through a neuron and onto the next neuron in order to facilitate communication.

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The nervous system is comprised of two primary cell types: neurons and glial cells. Neurons act as the main information processors, and the communication between them is essential for all nervous system functions. Glial cells, or glia, primarily serve in supporting roles for the neurons.

Cells of the Nervous System

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

Neuronal Communication 

There are different types of neurotransmitters with different functions in the human body. Some of the major neurotransmitters include:
- Serotonin (Mood & sleep)
- Glutamate (Memory & learning)
- Dopamine (Mood, sleep, & learning)
- Acetylcholine (Muscle action & memory)
- Beta-endorphin (Pain & pleasure)
- Gamma-aminobutyric acide (Brain function & sleep)
- Norepinephrine (Heart, intestines, & alertness)

Major Neurotransmitters

Psychologists have gained much of their understanding regarding the functions of neurotransmitters by researching how various drugs affect individuals with psychological disorders.

Neurotransmitters and Drugs

Functioning as the central building blocks and core information processors of the nervous system, neurons are interconnected cells essential for all tasks the system performs. The human brain contains around 100 billion neurons at birth. Their role encompasses everything from simple reflexes to complex cognitive functions.

Neurons

Glial cells, or glia, are a primary cell type in the nervous system that provides crucial physical and metabolic support to neurons. Their functions include creating a structural scaffold for the nervous system, insulating neurons, helping neurons align to facilitate communication, transporting nutrients and waste, and mediating immune responses.

Glial Cells

Based on the fundamental roles of the two primary cell types in the nervous system, which type of cell is most likely malfunctioning in this patient's condition, and why?

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