The control systems: nervous and endocrine
Nick Draper, Helen Marshall in Exercise Physiology, 2014
Astrocytes are the most abundant CNS neuroglia and have several functions which include providing support for neurons, maintaining chemical balance and regulating nervous tissue growth. Ependymal cells line the central cavities of the brain and spinal cord and have hair-like structures protruding from them called microvilli and cilia which help with the flow of cerebrospinal fluid (CSF). Microglia are involved in repair of neurological tissue and help by removing debris from the interstitial environment. Oligodendrocytes are responsible for creating a myelin sheath around neurons of the CNS and to create a structural framework for the CNS. Schwann cells are the equivalent of oligodendrocytes in the PNS and, as can be seen in Figure 4.3, each Schwann cell is responsible for myelination of one section of a neuronal axon. Schwann cells also have a role in providing a coordinated structure and protection for unmyelinated neurons and can enclose up to 10 or 20 of these neurons. Satellite cells (Figure 4.3), the second form of neuroglia found in the PNS, help to supply nutrients to the surrounding neurons.
Nervous system
David Sturgeon in Introduction to Anatomy and Physiology for Healthcare Students, 2018
The next type of glial cell found in the CNS are microglia. As their name suggests, they are the smallest of the glial cells and function primarily as phagocytic immune cells. They are highly mobile and move through the nervous tissue removing cellular debris, waste products and other material including microorganisms. The final type of support cell found in the CNS are specialised epithelial cells called ependymal cells. Like epithelial cells found elsewhere in the body, many of these are ciliated (i.e. they possess tiny hair-like projections). Ependymal cells line the ventricles (cavities) of the brain and the central canal of the spinal cord, and contribute to the secretion of cerebrospinal fluid (see below). The beating of their cilia also helps to direct the flow of cerebrospinal fluid around the CNS and filter out debris and foreign particles. Since the peripheral nervous system is mainly composed of axons, there are only two types of support cell: satellite cells and Schwann cells. The first are similar in function to astrocytes and surround and support neuronal cell bodies found in clusters called ganglia. They also help to control and maintain the chemical environment around the neurons they support. Schwann cells are the principle glial cells of the peripheral nervous system and, as we already know, are functionally similar to oligodendrocytes. They manufacture myelin, maintain the axon and contribute to the removal of cellular debris.
Blood–Brain Barrier and Cerebrospinal Fluid (CSF)
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2020
CSF circulates through the ventricular system and the subarachnoid space from the formation sites to the absorption sites and has a hydrostatic pressure of 6.5–20 cmH2O (or 5–15 mmHg). Ciliary movements of the ependymal cells propel the CSF towards the fourth ventricle and the foramina of Luschka and Magendie into the cisterna magna. From the cisterna magna, CSF passes superiorly into the subarachnoid space around the cerebellar hemispheres, caudally into the spinal subarachnoid space, and cephalad to the basilar cisterns (around the premedullary pontine and interpeduncular cisterns). From the basilar cisterns, CSF flows through the pre-chiasmatic cistern and Sylvian fissure to the lateral and frontal cortical regions, and by a second route to the medial and posterior part of the cerebral cortex (Figure 5.2). Respiratory oscillations and arterial pulsations of the cerebral arteries and choroid plexus provide additional momentum for the movement of CSF.
Proteomic examination of the neuroglial secretome: lessons for the clinic
Published in Expert Review of Proteomics, 2020
Jong-Heon Kim, Ruqayya Afridi, Won-Ha Lee, Kyoungho Suk
Glial cells are non-neuronal cells that constitute half of the brain tissue [1,2]. These cells play diverse homeostatic and supportive roles in brain development and function. Previously regarded as simply the glue of the brain, glial cells are now recognized as important functional cells in the brain, with perturbations in their functions leading to a pathological state [1]. Glial cells are in a continuous, intimate association with neurons and regulate neuronal functioning in multiple ways [3]. These cells are classified into four major types, namely astrocytes, microglia, oligodendrocytes, and ependymal cells, each with a distinct role in maintaining brain homeostasis. Astrocytes are the most abundant glial cells and regulate neuronal function by providing metabolites, ion homeostasis, recycling neurotransmitters, and synaptogenesis [4]. Microglia are the brain resident macrophages, surveying the brain parenchyma to protect it from noxious stimuli. Microglia also play an important role in synaptogenesis during brain development [5,6]. Oligodendrocytes, another important class of glial cells, are myelin-producing cells that provide neuronal axons with metabolic support and regulate action potentials through saltatory conduction. Ependymal cells are ciliated glial cells that line the ventricular surface of the brain and regulate the cerebrospinal fluid (CSF).
Cerebral gliomas: Treatment, prognosis and palliative alternatives
Published in Progress in Palliative Care, 2018
Dharam Persaud-Sharma, Joseph Burns, Marien Govea, Sanaz Kashan
The brain is a complex organ composed of multiple cell types, layers, and strata. One of the primary cell types of brain tissue includes glial cells which serve countless roles in the human brain. Glial cells can be subdivided into numerous categories, each with a specific function. Gliomas are tumors of glial cells that affect the human brain and spinal cord. They most frequently arise from three cell types: astrocytes, oligodendrocytes, and ependymal cells.1 Astrocytes are the most abundant glial cell in the brain and act primarily as supporting cells to the neurons. Oligodendrocytes function in myelin production in order to accelerate propagation of action potentials between neurons. Astrocytes give rise to astrocytomas; oligodendrocytes give rise to oligodendrocytomas, and a mix of both cell types gives rise to oligoastrocytomas.2
Early life stress decreases cell proliferation and the number of putative adult neural stem cells in the adult hypothalamus
Published in Stress, 2021
Pascal Bielefeld, Maralinde R. Abbink, Anna R. Davidson, Niels Reijner, Oihane Abiega, Paul J. Lucassen, Aniko Korosi, Carlos P. Fitzsimons
In addition to the hippocampus, several ‘non-canonical’ neurogenic niches have been recently described in the adult mammalian brain, including the rodent hypothalamus (Yoo and Blackshaw 2018; Feliciano et al., 2015; Kokoeva et al., 2007; Xu et al., 2005). This novel hypothalamic neurogenic niche has been observed in mouse, sheep and human brains (Batailler et al., 2014; Pellegrino et al., 2018). The identity of putative NSPC populations generating new neurons in the hypothalamus is still being investigated, but most studies point toward populations of tanycytes that express NSPC markers such as Nestin, Sox2, or vimentin (Haan et al., 2013; Lee et al., 2012; Robins et al., 2013a). In mice, hypothalamic tanycytes are divided in four types based on their cell type marker expression and localization: α1, α2, β1 and β2. While all α- and β-tanycytes co-express putative NSPC markers such as Sox2 and Nestin, they differ in their localization relative to the 3rd ventricle wall. α-Tanycytes are located more dorsally, while β-tanycytes occupy more ventral parts of the 3rd ventricle ependyma (Goodman and Hajihosseini, 2015). In addition, while the processes of α-tanycytes project horizontally to terminate in close proximity to the dorsomedial and ventromedial hypothalamic nucleus (α1) as well as the dorsomedial part of the arcuate nucleus (α2), the processes from β-tanycytes curve to contact the hypothalamic parenchymal capillaries in the arcuate nucleus (β1) or the portal blood vessels of the median eminence (ME) (β2) (Prevot et al., 2018; Rizzoti and Lovell-Badge, 2017; Rodriguez et al., 2005).
Related Knowledge Centers
- Central Nervous System
- Cerebrospinal Fluid
- Glia
- Simple Columnar Epithelium
- Ventricular System
- Spinal Cord
- Brain
- Neuroepithelial Cell
- Central Canal
- Neuroregeneration