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Homo Sapiens (“Us”): Strengths and Weaknesses
Published in Michael Hehenberger, Zhi Xia, Huanming Yang, Our Animal Connection, 2020
Michael Hehenberger, Zhi Xia, Huanming Yang
A nerve is defined as a cable-like, enclosed, bundle of axons (nerve fibers, projections of neurons) in the peripheral nervous system. It typically conducts electrical impulses known as action potentials, away from the nerve cell body. Axons transmit information to different neurons, muscles, and glands by having electrochemical impulses travel from peripheral organs to the cell body. This information is then propagated from the cell body to the spinal cord. In addition to neurons, nerves also include non-neuronal cells that coat the axons in myelin. There are two types of axons in the nervous system, namely myelinated and unmyelinated axons. Myelin is a layer of a fatty insulating substance and plays an important role in brain health.
Homo Sapiens (“Us”): Strengths and Weaknesses
Published in Michael Hehenberger, Zhi Xia, Our Animal Connection, 2019
A nerve is defined as a cable-like, enclosed, bundle of axons (nerve fibers, projections of neurons) in the peripheral nervous system. It typically conducts electrical impulses known as action potentials, away from the nerve cell body. Axons transmit information to different neurons, muscles, and glands by having electrochemical impulses travel from peripheral organs to the cell body. This information is then propagated from the cell body to the spinal cord. In addition to neurons, nerves also include non-neuronal cells that coat the axons in myelin. There are two types of axons in the nervous system, namely myelinated and unmyelinated axons. Myelin is a layer of a fatty insulating substance and plays an important role in brain health.
Computational Neuroscience and Compartmental Modeling
Published in Bahman Zohuri, Patrick J. McDaniel, Electrical Brain Stimulation for the Treatment of Neurological Disorders, 2019
Bahman Zohuri, Patrick J. McDaniel
Figure 3.5 illustrates the parts of a nerve cell or neuron. Each neuron consists of a cell body, or soma, that contains a cell nucleus. Branching out from the cell body are a number of fibers called dendrites and a single long fiber called the axon. The axon stretches out for a long distance, much longer than the scale in this diagram indicates. Typically, an axon is 1 cm long (100 times the diameter of the cell body) but can reach up to 1 meter. A neuron makes connections with 10 to 100,000 other neurons at junctions called synapses. Signals are propagated from neuron to neuron by a complicated electrochemical reaction. The signals control brain activity in the short term and also enable long-term changes in the connectivity of neurons. These mechanisms are thought to form the basis for learning in the brain. Most information processing goes on in the cerebral cortex, the outer layer of the brain. The basic organizational unit appears to be a column of tissue about 0.5 mm in diameter, containing about 20,000 neurons and extending the full depth of the cortex about 4 mm in humans).38
Emerging memristive neurons for neuromorphic computing and sensing
Published in Science and Technology of Advanced Materials, 2023
Zhiyuan Li, Wei Tang, Beining Zhang, Rui Yang, Xiangshui Miao
Despite this great variety, they all have a typical neuronal structure, comprising of three main parts: (i) Dendrites, which are the tree-root-shaped part of the neuron which are usually extending from the soma. Dendrites receive neural signals from pre-synaptic neurons and then transmit them to soma. It has been found that many complex calculations can be done in dendrites before the signal reaches soma, including Boolean operating, coincidence detecting, etc [44,45]. (ii) The soma, also called cell body, which is the essential center of the neuron. The soma synthetizes neurotransmitters, generates an action potential and then sends it to the axon. (iii) The axon, also referred to as nerve fiber, is a tail-like structure of the neuron which joins the soma at a junction called the axon hillock, acting as the output channel of neuron signals in biological system. The function of the axon is to transmit neuron signals away from the soma to the post-synaptic neurons.
Why slow axonal transport is bidirectional – can axonal transport of tau protein rely only on motor-driven anterograde transport?
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Ivan A. Kuznetsov, Andrey V. Kuznetsov
Due to the great length of axons, neurons must rely on a complicated “railway” system composed of microtubules (MTs). Various cargos are transported along MTs while pulled by molecular motors. Typically, newly synthesized cargos are transported in the anterograde direction (from the soma to the axon terminal) by molecular motors that belong to the kinesin superfamily. Cargos that need to be recycled in the somatic lysosomes are transported in the retrograde direction by molecular motors that belong to the dynein superfamily. Axonal transport is classified into fast anterograde axonal transport, which is driven by kinesin motors (representative velocity 1 μm s−1), fast retrograde axonal transport, which is driven by dynein motors (representative velocity is also 1 μm s−1), and slow axonal transport (SAT) (Morfini et al. 2012; Brown 2016; Roy 2020; Sleigh et al. 2019; Guedes-Dias and Holzbaur 2019).
Effect of axonal fiber architecture on mechanical heterogeneity of the white matter—a statistical micromechanical model
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Hesam Hoursan, Farzam Farahmand, Mohammad Taghi Ahmadian
Human brain white matter consists of axonal bundles which connect nerve cell bodies mostly located in the grey matter. A sudden inertial loading on the head can cause Diffuse Axonal Injury (DAI) of white matter, which involves axonal damage in a variety of modes. Among the failure modes of axons, rapid stretching of neural tracts, leading to the impairment of axoplasmic transport and subsequent swelling and neuropathologic problems, has been reported to be the prevailing failure mode (McKenzie et al. 1996; Smith and Meaney 2000; Di Pietro 2013). DAI tends to occur in three anatomical regions of white matter, known as the “injury triad”: the lobar white matter (including corona radiata), the corpus callosum, and the dorsolateral quadrant of the rostal brainstem, adjacent to the superior cerebellar peduncle (Tsao 2012).