Disorders of the nervous system
Judy Bothamley, Maureen Boyle in Medical Conditions Affecting Pregnancy and Childbirth, 2020
The axon is the output process of the neuron. Specialised cell junctions called synapses between the axon and other cells allow for efficient communication between cells. The input region comprises a complex arrangement of processes called dendrites. One axon (output) will synapse onto many different neurons, and a dendrite will receive inputs from many neurons. Neurotransmitters are released across this synapse, and once a critical point is reached, an electrical (nerve) impulse (action potential) is fired down the axon. Some neurotransmitters, such as glutamate, are excitatory, triggering depolarisation of the post-synaptic membrane and thus producing an action potential. Inhibitory neurotransmitters such as gamma-aminobutyric acid decrease the chance of post-synaptic action potential8.
Disorders of the nervous system
Judy Bothamley, Maureen Boyle in Medical Conditions Affecting Pregnancy and Childbirth, 2020
The axon is the output process of the neurone. Specialised cell junctions called synapses between the axon and other cells allow for efficient communication between cells. The input region comprises a complex arrangement of processes called dendrites. One axon (output) will synapse onto many different neurones and a dendrite will receive inputs from many neurones. Neurotransmitters are released across this synapse and once a critical point is reached an electrical (nerve) impulse (action potential) is fired down the axon. Some neurotransmitters, such as glutamate, are excitatory, triggering depolarisation of the post-synaptic membrane and thus producing an action potential. Inhibitory neurotransmitters such as gamma-aminobutyric acid (GABA) decrease the chance of post-synaptic action potential (Manford, 2003).
Pharmacological Management of Amyotrophic Lateral Sclerosis
Sahab Uddin, Rashid Mamunur in Advances in Neuropharmacology, 2020
Neurons lengthen their axons in excess of extensive distances during developing connections with other synaptic neurons. Proteins involved in guiding the axon may control the progression of axon guidance. These proteins can play a function in attracting or repelling axons thus guide them to a definite area or stopping them from rising into unsuitable regions, correspondingly. Recently several report sustain the testing theory that abnormal expression or function of axon guiding proteins such as ephrins, semaphorins, slits, and netrins usually implicated in curating and maintaining circuits of motor neuron may bring on pathological variations in circuits of motor neuron (Hollis, 2015). Interestingly, pathological variations occurring in nerve terminals and motor axons are found to lead degeneration of motor neurons and associated clinical abnormalities (Fischer et al., 2004). It can be inferred from this discovery that the disease development may begin at the nerve endings and ultimately grow toward the body of the neuronal cell. Numerous diverse molecules responsible for guiding the axons changed expressions in patients of ALS. Thus single-nucleotide polymorphisms (SNPs) in genes expressing proteins for axon guidance may important for diagnosis of ALS (Lesnick et al., 2008). After realizing the importance of these proteins, recently the cell replacement strategies have been designed for corrections of the degenerating motor system of these patients (Silva and Yu, 2008).
The Brain in Search of Itself: Santiago Ramón y Cajal and the Story of the Neuron
Published in Journal of the History of the Neurosciences, 2023
Douglas J. Lanska
Notably, Cajal distinguished dendrites from axons, and inferred that these serve different functions, the dendrites acting as conduits of information to the cell body from other nerves, and the axons acting as conduits of information away from the cell body to other neurons. He further determined that (1) the terminals of one neuron’s axon communicate with the dendrites of other neurons at specialized sites, later termed synapses by English neurophysiologist Charles Sherrington (1857–1952); (2) neurons do not communicate indiscriminately with other neurons, but instead have “connection specificity,” so that signals can travel along specific neural circuits in a predictable way; and (3) (with Belgian anatomist and neurologist Arthur van Gehuchten) neurons have “dynamic polarization,” meaning that signals in a neuron or neural circuit travel in only one direction.
Molecular mechanisms governing axonal transport: a C. elegans perspective
Published in Journal of Neurogenetics, 2020
Amruta Vasudevan, Sandhya P. Koushika
Axonal transport is a critical process, central to neuronal function and maintenance. In vitro studies have provided a wealth of information about single and ensemble motor behaviours in different cytoskeletal geometries (Holzbaur & Goldman, 2010). Super resolution imaging techniques, such as single molecule localization microscopy, allow researchers to examine complex in vivo cytoskeletal geometries. Recent studies have succeeded in resolving individual microtubules in axons of cultured hippocampal neurons, using anti-tubulin nanobodies to stain microtubules, and a novel optical nanoscopy technique, named motor-PAINT, to assess the stability and orientation of individual microtubules (Mikhaylova et al., 2015; Tas et al., 2017). Such techniques, when applied to model organisms, can pave the way for investigating mechanisms by which motor-cargo complexes exhibit a preference for specific microtubules in vivo, for instance, to understand the role of post-translational modifications of microtubules in track selection by motors. Advanced microscopy techniques such as STORM (He et al., 2016; Stewart & Shen, 2015) and Expansion microscopy (Yu et al., 2020) have already begun to provide insights into the cytoskeletal architecture and synaptic organization of C. elegans neurons. These techniques allow investigators to translate the precision of in vitro measurements to in vivo systems.
Current concepts review: peripheral neuropathies of the shoulder in the young athlete
Published in The Physician and Sportsmedicine, 2020
Tamara S. John, Felicity Fishman, Melinda S. Sharkey, Cordelia W. Carter
Peripheral neuropathies of the shoulder and upper extremity in the young athletic population – older children, adolescents and young adults – are uncommon, yet may result in significant pain and impairment. It is therefore important to understand the relevant anatomy, common injury mechanisms, characteristic clinical presentation, pertinent physical examination findings, diagnostic tools, treatment options and functional outcomes for these injuries. Furthermore, familiarity with standard terminology for nerve injuries is essential. Neuropraxia is the mildest nerve injury type, in which the nerve structure and its primary elements remain intact, but the myelin sheath is disrupted. The cause of a neurapraxia is typically a stretch mechanism and neurapraxias are often associated with complete functional recovery. Axonotmesis is a nerve injury in which the axon itself is disrupted in addition to its myelin sheath, although the endoneurial tubes and supportive tissues (perineurium, epineurium) remain intact. The mechanism of axonotmesis is typically a more severe stretch or crushing-type injury of the neural tissue. Finally, neurotmesis is the most severe form of nerve injury, in which there is complete nerve disruption. Neurotmetic injuries have the least potential for recovery. Fortunately, most sports-related peripheral neuropathies are either neurapraxic or axonotmetic in nature, rather than fully neurotmetic.
Related Knowledge Centers
- Action Potential
- Central Nervous System
- Neurological Disorder
- Peripheral Nervous System
- Sensory Neuron
- Neuron
- Soma
- Afferent Nerve Fiber
- Group A Nerve Fiber
- Group B Nerve Fiber