Cerebrospinal fluidCerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the brain, and absorbed in the arachnoid granulations. There is about 125 mL of CSF at any one time, and about 500 mL is generated every day. CSF acts as a shock absorber, cushion or buffer, providing basic mechanical and immunological protection to the brain inside the skull.
Subarachnoid hemorrhageSubarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space—the area between the arachnoid membrane and the pia mater surrounding the brain. Symptoms may include a severe headache of rapid onset, vomiting, decreased level of consciousness, fever, weakness, numbness, and sometimes seizures. Neck stiffness or neck pain are also relatively common. In about a quarter of people a small bleed with resolving symptoms occurs within a month of a larger bleed.
Shear rateIn physics, shear rate is the rate at which a progressive shearing deformation is applied to some material. The shear rate for a fluid flowing between two parallel plates, one moving at a constant speed and the other one stationary (Couette flow), is defined by where: is the shear rate, measured in reciprocal seconds; v is the velocity of the moving plate, measured in meters per second; h is the distance between the two parallel plates, measured in meters. Or: For the simple shear case, it is just a gradient of velocity in a flowing material.
Pressure-gradient forceIn fluid mechanics, the pressure-gradient force is the force that results when there is a difference in pressure across a surface. In general, a pressure is a force per unit area across a surface. A difference in pressure across a surface then implies a difference in force, which can result in an acceleration according to Newton's second law of motion, if there is no additional force to balance it. The resulting force is always directed from the region of higher-pressure to the region of lower-pressure.
Volumetric flow rateIn physics and engineering, in particular fluid dynamics, the volumetric flow rate (also known as volume flow rate, or volume velocity) is the volume of fluid which passes per unit time; usually it is represented by the symbol Q (sometimes ). It contrasts with mass flow rate, which is the other main type of fluid flow rate. In most contexts a mention of rate of fluid flow is likely to refer to the volumetric rate. In hydrometry, the volumetric flow rate is known as discharge.
Mass transferMass transfer is the net movement of mass from one location (usually meaning stream, phase, fraction or component) to another. Mass transfer occurs in many processes, such as absorption, evaporation, drying, precipitation, membrane filtration, and distillation. Mass transfer is used by different scientific disciplines for different processes and mechanisms. The phrase is commonly used in engineering for physical processes that involve diffusive and convective transport of chemical species within physical systems.
Perivascular spaceA perivascular space, also known as a Virchow–Robin space, is a fluid-filled space surrounding certain blood vessels in several organs, including the brain, potentially having an immunological function, but more broadly a dispersive role for neural and blood-derived messengers. The brain pia mater is reflected from the surface of the brain onto the surface of blood vessels in the subarachnoid space. In the brain, perivascular cuffs are regions of leukocyte aggregation in the perivascular spaces, usually found in patients with viral encephalitis.
PressurePressure (symbol: p or P) is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled gage pressure) is the pressure relative to the ambient pressure. Various units are used to express pressure. Some of these derive from a unit of force divided by a unit of area; the SI unit of pressure, the pascal (Pa), for example, is one newton per square metre (N/m2); similarly, the pound-force per square inch (psi, symbol lbf/in2) is the traditional unit of pressure in the imperial and US customary systems.
Pressure gradientIn atmospheric science, the pressure gradient (typically of air but more generally of any fluid) is a physical quantity that describes in which direction and at what rate the pressure increases the most rapidly around a particular location. The pressure gradient is a dimensional quantity expressed in units of pascals per metre (Pa/m). Mathematically, it is the gradient of pressure as a function of position. The negative gradient of pressure is known as the force density.
Strain rateIn materials science, strain rate is the change in strain (deformation) of a material with respect to time. The strain rate at some point within the material measures the rate at which the distances of adjacent parcels of the material change with time in the neighborhood of that point. It comprises both the rate at which the material is expanding or shrinking (expansion rate), and also the rate at which it is being deformed by progressive shearing without changing its volume (shear rate).
Fluid dynamicsIn physics, physical chemistry and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids—liquids and gases. It has several subdisciplines, including aerodynamics (the study of air and other gases in motion) and hydrodynamics (the study of liquids in motion). Fluid dynamics has a wide range of applications, including calculating forces and moments on aircraft, determining the mass flow rate of petroleum through pipelines, predicting weather patterns, understanding nebulae in interstellar space and modelling fission weapon detonation.
Frontotemporal dementiaFrontotemporal dementia (FTD), or frontotemporal degeneration disease, or frontotemporal neurocognitive disorder, encompasses several types of dementia involving the progressive degeneration of frontal and temporal lobes. FTDs broadly present as behavioral or language disorders with gradual onsets. Common signs and symptoms include significant changes in social and personal behavior, apathy, blunting of emotions, and deficits in both expressive and receptive language.
Central nervous systemThe central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all parts of the bodies of bilaterally symmetric and triploblastic animals—that is, all multicellular animals except sponges and diploblasts. It is a structure composed of nervous tissue positioned along the rostral (nose end) to caudal (tail end) axis of the body and may have an enlarged section at the rostral end which is a brain.
MeningesIn anatomy, the meninges (məˈnɪndʒiːz, : meninx (ˈmiːnɪŋks or ˈmɛnɪŋks), ) are the three membranes that envelop the brain and spinal cord. In mammals, the meninges are the dura mater, the arachnoid mater, and the pia mater. Cerebrospinal fluid is located in the subarachnoid space between the arachnoid mater and the pia mater. The primary function of the meninges is to protect the central nervous system. Dura mater The dura mater (tough mother) (also rarely called meninx fibrosa or pachymeninx) is a thick, durable membrane, closest to the skull and vertebrae.
Mass flow rateIn physics and engineering, mass flow rate is the mass of a substance which passes per unit of time. Its unit is kilogram per second in SI units, and slug per second or pound per second in US customary units. The common symbol is (ṁ, pronounced "m-dot"), although sometimes μ (Greek lowercase mu) is used. Sometimes, mass flow rate is termed mass flux or mass current, see for example Schaum's Outline of Fluid Mechanics. In this article, the (more intuitive) definition is used. Mass flow rate is defined by the limit: i.
Intracranial pressureIntracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury (mmHg) and at rest, is normally 7–15 mmHg for a supine adult. The body has various mechanisms by which it keeps the ICP stable, with CSF pressures varying by about 1 mmHg in normal adults through shifts in production and absorption of CSF. Changes in ICP are attributed to volume changes in one or more of the constituents contained in the cranium.
Frontotemporal lobar degenerationFrontotemporal lobar degeneration (FTLD) is a pathological process that occurs in frontotemporal dementia. It is characterized by atrophy in the frontal lobe and temporal lobe of the brain, with sparing of the parietal and occipital lobes. Common proteinopathies that are found in FTLD include the accumulation of tau proteins and TAR DNA-binding protein 43 (TDP-43). Mutations in the C9orf72 gene have been established as a major genetic contribution of FTLD, although defects in the granulin (GRN) and microtubule-associated proteins (MAPs) are also associated with it.
Computational fluid dynamicsComputational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structures to analyze and solve problems that involve fluid flows. Computers are used to perform the calculations required to simulate the free-stream flow of the fluid, and the interaction of the fluid (liquids and gases) with surfaces defined by boundary conditions. With high-speed supercomputers, better solutions can be achieved, and are often required to solve the largest and most complex problems.
Heat transferHeat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes. Engineers also consider the transfer of mass of differing chemical species (mass transfer in the form of advection), either cold or hot, to achieve heat transfer.
Cerebrospinal fluid leakA cerebrospinal fluid leak (CSF leak or CSFL) is a medical condition where the cerebrospinal fluid (CSF) surrounding the brain or spinal cord leaks out of one or more holes or tears in the dura mater. A cerebrospinal fluid leak can be either cranial or spinal, and these are two different disorders. A spinal CSF leak can be caused by one or more meningeal diverticula or CSF-venous fistulas not associated with an epidural leak.
