Sensory System Vs Neurons

* White matter is one of the two components of the central nervous system, and it consists of glial cells and myelinated axons that transmit signals from one region of the cerebrum to another as well as in between the cerebrum and lower brain centers. Grey matter contains neural cell bodies. Unlike white matter, it is mostly made up of myelinated axon tracts. Tracts are bundles of fibers that connect to different parts of the CNS. Roots receive information sent by neurons. Spinal nerves refer to a mixture of spinal nerves, which carry

The nervous system is made up of basic units called neurons. The main role of the neurons is to receive, integrate and transmit information throughout the body. There are some neuroglial cells found in nervous system aswell which provide support to the neurons by giving protection and nourishment Neurons have nerve processes that looks like finger like projections extended from the nerve cell body. They also contain axons and dendrites which enable them to transmit signals throughout the body. Normally, axon carry signals away from the cell body and dendrites carry signals toward the cell body according to Regina Bailey (2013). Neurons have three different shapes: bipolar, unipolar and multipolar where bipolar has two neuronal processes coming out of the cell body, unipolar has only one neuronal process coming out of the cell body and multipolar has many neuronal processes coming out of the cell body.

a) The structures and the afferent division of the peripheral nervous system that are involved in

He noted the parallel lines of the mesolobe (corpus callosum), afterwards minutely described by Félix Vicq-d'Azyr. He seems to have recognised the communication of the convoluted surface of the brain and that between the lateral cavities beneath the fornix. He described the corpora striata and optic thalami; the four orbicular eminences, with the bridge, which he first named annular protuberance; and the white mammillary eminences, behind the infundibulum. In the cerebellum he remarks the arborescent arrangement of the white and grey matter and gives a good account of the internal carotids and the communications which they make with the branches of the basilar

Age-related declines are not constant across brain regions. Moreover, patterns of brain aging differs among individuals. Post mortem (PM) studies cannot help in assessment of brain tissue and its components. Moreover, PM cannot provide information on dynamic process of adult brain development, and its connection with brain structure and function. MRI helps in in-vivo measurements of the brain. It was realized that there is cortical thinning as age progresses. . Some studies of cortical thickness failed to replicate stability of the primary sensory regions (e.g., calcarine cortex) (Fjell et al., 2009; Salat et al., 2004) while others found that cortical thinning in frontal and parietal lobes exceed that of the temporal and occipital regions (Thambisetty et al., 2010). It is suggested that myelin is related to shrinkage in cerebral cortex or responsible for loss of cortical volume. MRI has helped evaluate leukoaraiosis which is a change in white matter integrity that is displayed on a T2-weighted MR image as a high signal intensity area. This area is defined as white matter hyperintensities (WMH) which depicts pathological processes such as ischemic lesions, gliosis, axonal degeneration, loss of myelin, microinfarcts, and expansion of perivascular spaces (de Leeuw et al., 2001; Pantoni, 1998). WHM is observed around the borders of the ventricles and deep in the subcortical WM regions. WHM is not present in health adults until the age of 50-55 (Hopkins et al., 2006). Further,

The CNS contains the brain and spinal cord. Its main functions include: processing, integrating, and coordinating sensory information and motor instructions. The sensory data conducts information that is being processed from internal and external conditions the body is experiencing. Motor commands regulate and control peripheral organs (skeletal muscles). The brain functions under memory, emotions, learning, and intelligence. The PNS consist of the neural tissue found outside of the CNS. It functions in sending data to the CNS which motor commands are than carried out to the peripheral tissues/systems. Multiple nerve fibers send sensory data and motor commands in the PNS. The nerves that assist with transmitting data include the cranial nerves and spinal nerve. However, the PNS can be divided into afferent (to bring in) and efferent (to bring out) divisions of transferring data. The afferent division functions in bringing in sensory data to the CNS. Sensory structures are receptors that detect internal/external environmental change and adjusting accordingly. The efferent division functions in carrying out motor commands from the CNS to glands, muscles, and adipose tissue. The efferent division contains somatic

Magnetic Resonance Imaging (MRI) is used to show the borders of white and gray matter in the brain. This can help to differentiate AD from multi infarct dementia and low pressure hydrocephalus based on the ratios of white and gray matter. A person with AD suffers from a loss of gray matter, thus making the ratio of gray to white matter smaller than in a person without AD. An exam of the body fluid and non-neural tissue can be helpful to differentiate between AD and other disorders and infections that cause changes in the blood and CSF. These tests also help to demonstrate the functionality of neurotransmitters, metabolites, and enzymes. Although these tests are useful, the only way to confirm that a patient definitely has AD is by autopsy

Brain consists of white matter and gray matter. While gray matter of brain contains nerve cells, white matter of brain contains nerve fibers and myelin. Nerve fibers connect the nerve cells and myelin covers the nerve fibers. Myelin is responsible for conduction of impulses. It also helps in insulation which prevents short circuits.

At least eight to ten layer V pyramidal neurons from the visual cortex monocular region were selected from each brain for analysis utilizing light microscopy. Each of these neurons had to have an apical dendrite of at least 80μm long and exhibited full Golgi impregnation represented by a lack of floating spine heads. Each neuron underwent analysis of the apical dendrite, and following regions if present: apical oblique (branch protruding from apical dendrite), first order basilar branch (branching directly from pyramidal cell), second order basilar branch (separated from first order branch), third order basilar branch (from second order branch) and forth order basilar branch (from third order branch). A segment of at least 10μm long and at least 2μm away from bifurcations, was selected from the structures mentioned above, and analyzed based on the number of dendritic spines and morphology of dendritic spines. Each dendritic spine was categorized based on similarity to 12 categories (Figure 1) modified from those described in Irwin et al., 2002 as seen in Figure 2. All final analyses were done under 100X magnification. Length of the each segment was recorded, as well as the thickness of the segment at the starting and end points. The segment thickness was recorded to ensure that any differences in dendritic spine density was not due to differences in dendritic branch thickness.

Myelin, that is prevalent in the white matter, is a protein-lipid substance formed by 20% of proteins and for the remaining part of lipids (Fig.4). It forms a coating around the axons that acts as an insulating sheath, preventing the electric fields dispersion and ensuring a more rapid and efficient conduction. Myelination begins in the late fetal period and continues for at least 20 years during the life of each individual. Its biosynthetic pathway occurs mainly in oligodendrocytes for the CNS and in the Schwann cells for the peripheral nervous system (PNS).

The weakened vessels also become leaky, causing fluid to seep into the retina. This fluid form sediment which is composed of lipids and proteins, and appeared as waxy, yellow deposits called hard exudates. As NPDR progresses, the affected vessels eventually become obstructed. This obstruction may cause infarction of the nerve fiber layer, resulting white patches called cotton wool spots (CWS).

The eventual correlation between serum levels of targeted sphingolipids and the microstructural characteristics of the brain white matter, assessed by DTI-NMR and, finally,

white matter of the nervous system, white matter is typically found at the centre of the brain, the

Within the human anatomy, an intricate and complex network of specialised nerve fibres and neurons works in collaboration with the central nervous system and peripheral system, designed to carry out the various actions humans perform every day. The nervous system is also known as the master control unit of the human body, as it operates other major functions such as the circulatory and respiratory systems (Jakab, 2006). It is composed of the central nervous system (CNS) and the peripheral nervous system (PNS). The neurons established within the various sections of the nervous system, is structured with three main parts: a dendrite which is a cluster of branches that operates by receiving information from the

Human brain consists of billions of cells interconnected together, with each performing its separate functions. It consists of two explicit categories of nerves: neurons and glia cells. Neuron is a single nerve cell in the entire nervous system; which is electrically excitable cell that carries information after being processed via chemical or electrical signals. One of its key characteristics is that it does not undergo cell division. In addition, it maintains a voltage gradient for all the neurons across its membranes. Glia cells, on the other hand, its functionality is to maintain homeostasis.