Basic Neural Units of the Brain: Neurons, Synapses and Action Potential (1906.01703v1)

Abstract: As a follow-up tutorial article of [29], in this paper, we will introduce the basic compositional units of the human brain, which will further illustrate the cell-level bio-structure of the brain. On average, the human brain contains about 100 billion neurons and many more neuroglia which serve to support and protect the neurons. Each neuron may be connected to up to 10,000 other neurons, passing signals to each other via as many as 1,000 trillion synapses. In the nervous system, a synapse is a structure that permits a neuron to pass an electrical or chemical signal to another neuron or to the target effector cell. Such signals will be accumulated as the membrane potential of the neurons, and it will trigger and pass the signal pulse (i.e., action potential) to other neurons when the membrane potential is greater than a precisely defined threshold voltage. To be more specific, in this paper, we will talk about the neurons, synapses and the action potential concepts in detail. Many of the materials used in this paper are from wikipedia and several other neuroscience introductory articles, which will be properly cited in this paper. This is the second of the three tutorial articles about the brain (the other two are [29] and [28]). The readers are suggested to read the previous tutorial article [29] to get more background information about the brain structure and functions prior to reading this paper.

• The paper provides a comprehensive overview of the fundamental cellular units of the brain: neurons, synapses, and action potentials.
• It details neuronal structure and function, including classifications and membrane potential, alongside synaptic connectivity mechanisms like chemical and electrical synapses.
• The paper thoroughly explains the dynamics of action potential generation and propagation, emphasizing underlying ionic movements and voltage-gated channels.

Overview of the Paper: Basic Neural Units of the Brain: Neurons, Synapses, and Action Potential

The paper "Basic Neural Units of the Brain: Neurons, Synapses, and Action Potential" authored by Jiawei Zhang offers an exhaustive overview of the fundamental cellular components of the human brain. It is a pivotal part of a tutorial series intended to elucidate the intricate workings of the brain from a biological perspective. The paper not only delineates the structural and functional aspects of neurons but also explores the complex interactions occurring at synapses and elaborates on the principles of action potentials.

Neuronal Structure and Function

The paper provides a detailed exposition of the neuron, described as a highly specialized, electrically excitable cell responsible for processing and transmitting information through electrochemical signaling. Each human brain neuron, totaling around 100 billion, connects to up to 10,000 others through synapses, allowing for the immense data processing capabilities characteristic of the human brain. Neurons are systematically classified based on structure (unipolar, bipolar, multipolar, etc.) and function (afferent, efferent, interneurons), illustrating their diverse roles in neural connectivity and information processing.

The document also discusses the critical role of the neuron's membrane potential, maintained by ion pumps and channels, which is integral to the generation of action potentials. These biophysical properties are fundamental to understanding how neurons transmit nerve impulses.

Synaptic Connectivity

At the core of nervous system functionality are synapses, which facilitate the passage of electrical or chemical signals between neurons or between neurons and effector cells. Synapses are broadly categorized into chemical and electrical types, each with distinct roles and mechanisms. The paper details how chemical synapses utilize neurotransmitter release to modulate post-synaptic response, whereas electrical synapses allow direct ion exchange through gap junctions for rapid signaling.

Additionally, the article explores synaptic vesicle dynamics and neurotransmitter types, shedding light on their roles in synaptic function and plasticity. This includes a discussion on neurotransmitter identification criteria and the wide variety of neurotransmitters involved in neural signaling, highlighting glutamate and GABA as major contributors to excitatory and inhibitory functions, respectively.

The Dynamics of Action Potential

The dynamic process of action potential generation and propagation is thoroughly dissected, detailing the phases of depolarization, repolarization, hyperpolarization, and their underlying ionic movements. The nuanced interplay of sodium and potassium channels, alongside their voltage-gated properties, illustrates the biophysical basis of the action potential—a fundamental process for neuronal communication.

The paper emphasizes the importance of understanding the refractory period, underscoring why action potentials propagate unidirectionally along axons. This exploration of action potential mechanics provides a foundational understanding necessary for further paper on neuronal signaling.

Implications and Future Directions

By demystifying the basic neural units, this paper lays the groundwork for deeper insights into more complex brain functions and diseases. Understanding neurons, synapses, and action potentials forms the basis for exploring neuronal network operations and, potentially, their dysregulation in neurological disorders.

The paper, as a part of a broader educational series, indicates that future work will aim to address higher-level cognitive functions such as perception and memory, building on the foundational biological mechanisms outlined. The insights from this manuscript are critical both for basic neuroscience research and for developing applications in neural technology and medicine.

In closing, the paper serves as a comprehensive resource for understanding the cell-level intricacies of the brain, catering to researchers looking to deepen their knowledge of neurobiological processes. As research progresses, these insights will potentially inform developments in synthetic biology, neuroprosthetics, and artificial intelligence systems inspired by human cognition.