Functional Neurology
James Crossley in Functional Exercise and Rehabilitation, 2021
Neurons clump together to form nerves. Nerves can be either sensory, motor or interconnecting. Sensory nerves, also known as afferent nerves, relay signals from the peripheral tissues and organs to the central nervous system (CNS). Afferent nerves provide the CNS with information regarding our environment. Motor, or efferent nerves, transmit signals from the CNS to the tissues and organs. These signals ‘activate’ or alter the function of peripheral tissues and organs. Motor signals sent from the CNS innervate muscles, making them contract, for example. Interneurons are so called because they communicate between or connect spinal and motor neurons, influencing and modulating neuronal function on yet another level. Nerves congregate in various areas of the body, the entirety of which we call the nervous system.
Mechanistic Aspects of Neurodegeneration in Alzheimer’s Disease and the Role of Phytochemicals as Restorative Agents
Atanu Bhattacharjee, Akula Ramakrishna, Magisetty Obulesu in Phytomedicine and Alzheimer’s Disease, 2020
Neurotransmitters, also known as endogenous chemical messengers, enable neurotransmission of signals across the chemical synapses. To maintain the homeostatic balance of neural circuits, diverse sets of inhibitory interneurons regulate the activity of excitatory neurons in the CNS. Impaired co-activation of excitatory and inhibitory neurons, such as substantial loss of gamma amino butyric acid (GABA)-ergic interneurons, dysfunction of interneurons due to loss of their afferent excitatory input, changes in their receptors, and an imbalance of the different neurotransmitters, like glutamate, acetylcholine, dopamine, and serotonin, have been proposed in many neurobiological disorders like AD. AD is a neurodegenerative disorder which is characterized by memory loss, and behavioral and psychological symptoms of dementia (Southwell et al., 2014). It is hypothesized that altered reuptake of neurotransmitters by vesicular glutamate transporters (VGLUTs), excitatory amino acid transporters (EAATs), the vesicular acetylcholine transporter (VAChT), the serotonin reuptake transporter (SERT), or the dopamine reuptake transporter (DAT), are involved in the neurotransmission imbalance in AD. Compared with control subjects, the protein and mRNA levels of VGLUTs, EAAT1–3, VAChT, and SERT are reduced significantly in AD subjects; playing a contributory role to the recognized cholinergic deficiency, alteration in glutamatergic recycling and reduced SERT levels could exacerbate depressive symptoms in AD (Isaacson and Scanziani, 2011).
The nervous system
Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella in Essentials of Human Physiology and Pathophysiology for Pharmacy and Allied Health, 2019
Interneurons, the third class of neurons, lie entirely within the CNS. The human brain and spinal cord contains well over 100 billion neurons, and interneurons account for approximately 99% of all the neurons within the body. Interneurons lie between afferent and efferent neurons and are responsible for integrating sensory input and coordinating a motor response. In the simplest condition, interneurons process responses at the level of the spinal cord in the form of reflexes, which are automatic, stereotyped responses to given stimuli. For example, stimulation of pain receptors generates action potentials in their associated afferent neurons. These impulses are transmitted to the spinal cord where the afferent neurons stimulate interneurons. These interneurons then stimulate efferent neurons that cause skeletal muscle contraction in the affected area to move the body part away from the painful stimulus. This withdrawal reflex involves comparatively few interneurons and does not require any input from higher nervous centers in the brain. On the other hand, a response to some other stimulus may involve more sophisticated neurological phenomena such as memory, motivation, judgment and intellect. This type of response is not automatic, is clearly far more complex and may require the activity of millions of interneurons in many regions of the brain prior to the stimulation of motor neurons to carry out the desired effect.
Split phenomenon of antagonistic muscle groups in amyotrophic lateral sclerosis: relative preservation of flexor muscles
Published in Neurological Research, 2021
Jingwen Liu, Zhili Wang, Dongchao Shen, Xunzhe Yang, Mingsheng Liu, Liying Cui
Nevertheless, the size differences in the cortical representations are difficult to exactly explain our study findings. For instance, the biceps has a more extensive cortical representation than the triceps [18,19]. However, in the present study, elbow extension was more vulnerable to weakness compared to elbow flexion. In addition to motor neurons, interneurons that release inhibitory neurotransmitters are diffusely distributed in the cortex and spinal cord and regulate a range of activities in the nervous system. Evidence from clinical and electrophysiological sources indicates that ALS patients may suffer from a loss of interneurons. Currently, it has been hypothesized that the dysfunction of interneurons may mediate the degeneration of upper motor neurons (UMN) and lower motor neurons (LMN) in ALS patients, ultimately causing the pathological hyperexcitability [20].
The osmotic demyelination syndrome: the resilience of thalamic neurons is verified with transmission electron microscopy
Published in Ultrastructural Pathology, 2020
Jacques Gilloteaux, Joanna Bouchat, Jean-Pierre Brion, Charles Nicaise
The fine structure observations here reported concerned both the ventral posterolateral (VPL) and ventral posteromedial (VPM) thalamic nuclei cell bodies. There, most are interneurons whose neuropil contain long entwined neurite’s extensions undergoing ODS myelinolysis, i.e. axons, dendrites and neuroglial structures that were investigated in other studies.72–74 It is also clear that, at ODS12h, the ultrastructure examination allowed to verify the demyelinating zones along with the surrounded intact region of the thalamus nuclei while LM aspects were not entirely able to show the fine changes whether damaged, undamaged or undergoing repairs. For each treatment, several examples of cell bodies were displayed in panes of Figures 5–15.
Low Fos expression in newly generated neurons of the main and accessory olfactory bulb following single maternal separation
Published in Stress, 2020
Monika Závodská, Kamila Fabianová, Marcela Martončíková, Adam Raček, Enikő Račeková
Neurogenesis of the local circuit neurons of the MOB and into a lesser extent of the AOB is not completed at the end of the embryonic period, rather continuing throughout life (Lois & Alvarez-Buylla, 1994; Oboti et al., 2009). Postnatal olfactory interneurons derive from neuronal stem cells located in the subventricular zone of the lateral ventricles (Doetsch et al., 2002) from where they migrate a long distance to the target structures – the MOB and AOB. Here, the neuroblasts differentiate into different types of interneurons, mainly the granule and periglomerular cells (Belluzzi et al., 2003; Carleton et al., 2003, Oboti et al., 2009; Luskin, 1993). Despite the recent knowledge about involvement of postnatal neurogenesis in several aspects of olfactory function such as, olfactory perceptual learning (Moreno et al., 2009), odor discrimination (Belnoue et al., 2011), and short-term and long-term odor memory (Breton-Provencher et al., 2009), the functional role of newly generated cells is still not sufficiently understood. Interestingly, the results of studies investigating the function of newborn neurons suggest that adult-born neurons differ from neurons generated during development in several properties (reviewed in Ming & Song, 2011).
Related Knowledge Centers
- Central Nervous System
- Motor Neuron
- Neural Oscillation
- Reflex
- Sensory Neuron
- Neurogenesis
- Neuron
- Neural Circuit
- Learning
- Decision-Making