Glia, Meninges, Ventricles, & the Blood Brain Barrier
Glia, Meninges, Ventricles, & the Blood Brain Barrier NROSCI 1000 - Intro to Neuroscience
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This 4 page Class Notes was uploaded by Svena Verma on Saturday September 24, 2016. The Class Notes belongs to NROSCI 1000 - Intro to Neuroscience at University of Pittsburgh taught by Linda Rinaman in Summer 2015. Since its upload, it has received 3 views. For similar materials see Intro to Neuroscience in Neuroscience at University of Pittsburgh.
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Date Created: 09/24/16
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Glia, Meninges, Ventricles, & the Blood Brain Barrier Glial cells - cells in the brain that support the neurons CNS contains 3-4x more glial cells than neurons; for every neuron there are 3-4 glial cells types of glial cells astrocytes oligodendrocytes (CNS) shwann cells (PNS) microglia/macrophages macrophages are derived from bone marrow macrophages diﬀerentiate into microglia ependymoglia cells that line the ventricles; interface between cerebral spinal ﬂuid and Astrocytes in close proximity with the blood vessels; usually where you will ﬁnd them restricted to CNS they help maintain the proper extracellular chemical environment necessary for neural signaling calcium regulating “end feet” that come into contact with capillary endothelial cells to maintain their tight junctions; these junctions comprise the blood brain barrier the astrocytes interacting with the tissue that forms the tight junctions also have a special role during early embryonic development astrocytes become radial glia cells; neuron Oligodendrocytes and Schwann cells - the glia that make myelin CNS: oligo PNS: shwann each glial cell lays down multiple layers of myelin (lipid membrane) to “insulate” myelinated axons Each oligodendrocyte myelinates several parts of several CNS axons Each Schwann cell myelinates one part of a single PNS axon (like beads on a chain) Microglia smallest glial cells multifunctional originally from the bone marrow - don’t develop as part of the brain/spinal chord, develop in the Periphery, and migrate to the CNS primary function: scavenger change their form back and forth multiple times (can become phagocytic and return to resting state) e.g. infection/stab wound: migrate in and help out, transform in many directions as necessary bacteria being gobbled up by macrophages with lysosomes that have enzymes that digest them down microglia secrete cytokines (signalling molecules) to call more macrophages into the area while the local microglia react to the situation they call macrophages to help out (via cytokine secretion) change the fastest, have the most plastic structure Ependymoglia line the inner surface of the ventricles not just providing the barrier; long processes that go into the tissue probably signaling into brain tissue in that area especially in the hypothalamus specialized form interacts with capillary cells and forms the choroid plexus choroid plexus is a vascularized tissue this secretes the cerebral spinal ﬂuid into the ventricular system Meninges encases the CNS (brain and spinal chord), protects it from trauma, maintains a ﬂuid cushion around the nervous system three protective layers of tissue surrounding the CNS 1. dura mater: hard, tough, can’t break through it dura mater comes oﬀ with the skull 2. arachnoid mater: spider like subarachnoid space 3. pia mater: tender matter, fragile and thin, completely covers everything, impossible to peel oﬀ, really thin and ﬁne pia layer folds in with all the gyri subarachnoid space between arachnoid and pia layers this space is ﬁlled with ﬂuid and also is occupied by major arteries and veins on the surface of the CNS left the ventricular system and entered the subarachnoid space meningitis: infection of the meninges; causes swelling and subsequent compression of the skull, leads to seizures and stroke viral meningitis bacterial meningitis (more serious, often fatal; immunization available) Ventricular System series of interconnected, ﬂuid-ﬁlled spaces within the core of the brain and spinal cord ﬁlled with cerebrospinal ﬂuid (CSF) 1. derived from the choroid plexus - a specialized capillary/ependymoglia tissue within the walls of ventricles; ﬁlters capillary blood and secretes the CSF product into the ventricles 2. Enters the lateral ventricles, third ventricle, through cerebral aqueduct into fourth ventricle 3. CSF leaves ventricles through several foramina to enter the subarachnoid space surrounding the brain/spinal cord 4. CSF then drains out of subarachnoid space through the arachnoid villi/granulations into subdural sinuses, then back into the general venous blood circulation Blockage in cerebral aqueduct can lead to swelling of the head due to swelling of the brain thin aquaduct is blocked, that ﬂuid has no where to go, ventricles swell and push the brains out usually happens in infants because their skulls haven’t fully formed yet called hydrocephalus blockage and build up of spinal ﬂuid Blood-brain Barrier NOT the role of the meninges, meninges BBBarrier = walls of the blood vessels in the brain Formed by the tight junctions between vascular (capillary) endothelial cells inside the brain and spinal cord these tight junctions are induced by astrocytic “end feet” which contact vascular endothelial cells Brain capillaries are NON-FENESTRATED (no windows) capillaries in the rest of the body’s tissues are FENESTRATED (with windows because they lack tight junctions/barriers) A few small, special brain regions do contain fenestrated capillaries . . . specialized for detecting toxins, hormones, etc. Circumventricular organs (on brain midline, adjacent to ventricles) area postrema near the fourth ventricle allow entry of other molecules that the rest of BBB will not keeps out proteins, hormones, toxins, bacteria, blood cells allows in oxygen, carbon dioxide, gases, glucose, insulin, amino acids, alcohol, nicotine, cocaine
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