3 Cellular base of nervous system 1 Cellular base of nervous system • Neuronal cells – Reception, integration and propagation of information – Unique, irreplaceable • Neuroglial cells – Support for neuronal cells – Easily replacable • The total amount of neuronal cells - 100 billions (1011) • Neruon/glia ratio – 1/10 - 50 (Principles of Neural Science, 4th ed., 2012) – 1/1 (Nolte´s Human Brain, 7th ed., 2015) 2 Cellular base of nervous system • Neuronal cells – Reception, integration and propagation of information – Unique, irreplaceable • Neuroglial cells – Support for neuronal cells – Easily replacable • The total amount of neuronal cells - 100 billions (1011) • Neruon/glia ratio – 1/10 - 50 (Principles of Neural Science, 4th ed., 2012) – 1/2 – 10 (Principles of Neural Science, 5th ed., 2012) – 1/1 (Nolte´s Human Brain, 7th ed., 2015) 3 Neuron http://www.slideshare.net/drpsdeb/presentations 4 Neuron http://www.slideshare.net/drpsdeb/presentations ✓ Signal reception ✓ Signal integration ✓ AP generatin ✓ AP propagation ✓ Signal transmission The inside of the cell The membrane ✓ … ✓ Synthesis ✓ Transport ✓ … 5 https://upload.wikimedia.org/wikipedia/commons/e/ed/Neuron_Cell_Body.png Maintain Activity 6 https://upload.wikimedia.org/wikipedia/commons/e/ed/Neuron_Cell_Body.png Maintain Activity 7 http://www.oapublishinglondon.com/images/article/pdf/1397255957.pdf Maintain Activity 8 Membrane potential • Due to differences in the concentrations of ions on opposite sides of a cellular membrane http://www.slideshare.net/drpsdeb/presentations 9 Resting membrane potential of a neuron • Highly instable state of membrane • Why? – Speed! • Brain sonsumption ✓Oxygen - 20% of total body consumption ✓Glucose – 25% of total body consumption http://assassinscreed.ubi.com 10 Action potential • Quick voltage change on the membrane • Spreads along the axon • All or nothing principle http://www.slideshare.net/drpsdeb/presentations 11 Action potential spreading • Local currents • Anterograde http://www.slideshare.net/drpsdeb/presentations 12 Saltatory conduction http://www.slideshare.net/drpsdeb/presentations • Myelin sheat • Nodes of ranvier • Economy • Speed of conduction • Speed of conduction also dependent of nerve fibre diameter – the electrical resistance is inversly proportional to area of cross-section 13 Classification of nerve fibers • In humans mostly myelinated • All fibers are myelinated in CNS • Non-myelinated are evolutionary old ones http://neuroscience.uth.tmc.edu/s2/chapter04.html 14 Neuronal classification http://www.slideshare.net/CsillaEgri/presentations 15 Neuronal classification http://www.slideshare.net/CsillaEgri/presentations 16 Neuronal classification http://www.slideshare.net/CsillaEgri/presentations 17 Neuroglial cells Central nervous system • Astrocytes – Hematoencephalic b. – Homeostasis maintaining – Metabolism of neurotransmitters – Important during brain development 18 Neuroglial cells Central nervous system • Astrocytes – Hematoencephalic b. – Homeostasis maintaining – Metabolism of neurotransmitters – Important during brain development • Oligodendrocytes – Myelin sheat 19 Neuroglial cells Central nervous system • Astrocytes – Hematoencephalic b. – Homeostasis maintaining – Metabolism of neurotransmitters – Important during brain development • Oligodendrocytes – Myelin sheat • Microglia – Immune funtion 20 Neuroglial cells Central nervous system • Astrocytes – Hematoencephalic b. – Homeostasis maintaining – Metabolism of neurotransmitters – Important during brain development • Oligodendrocytes – Myelin sheat • Microglia – Immune funtion • Ependymal cells – Choroid plexus – (hemato-liquor barrier) – Ventricular lining (liquro-encephalic barrier) 21 Neuroglial cells Central nervous system • Astrocytes – Hematoencephalic b. – Homeostasis maintaining – Metabolism of neurotransmitters – Important during brain development • Oligodendrocytes – Myelin sheat • Microglia – Immune funtion • Ependymal cells – Choroid plexus – (hemato-liquor barrier) – Ventricular lining (liquro-encephalic barrier) Peripheral nervous system • Satelite cells – Support functions in PNS 22 Neuroglial cells Central nervous system • Astrocytes – Hematoencephalic b. – Homeostasis maintaining – Metabolism of neurotransmitters – Important during brain development • Oligodendrocytes – Myelin sheat • Microglia – Immune funtion • Ependymal cells – Choroid plexus – (hemato-liquor barrier) – Ventricular lining (liquro-encephalic barrier) Peripheral nervous system • Satelite cells – Support functions in PNS • Schwan cells – Myelin sheat 23 Compartmentalization • Cellular specialization leads to compartmentalization on several levels – Tissue level – Organ level – Organ system level • There are barriers in between compartments • Properties/content may vary among different compartments 24 Cellular base of nervous system The brain homeostasis is maintained within a narrow range thanks to hematoencephalic barrier and astrocyte activity 25 Cellular base of nervous system The brain homeostasis is maintained within a narrow range thanks to hematoencephalic barrier and astrocyte activity This allows neuronal cells to live for the entire life of the individual 26 Intracranial compartment http://edutoolanatomy.wikispaces.com v v http://www.corpshumain.ca/en/Cerveau3_en.php • Brain • Cerebrospinal fluid • Blood (intravasculary) • Barriers – Meningeal – Hematoliquor – Hematoencephalic 27 Meningeal and hematoliquor barrier https://sisu.ut.ee/histology/meninges https://sisu.ut.ee/histology/meninges 28 Cerebrospinal fluid http://www.control.tfe.umu.se PCh AG • Clear fluid produced by active secretion • Liquor space ➢ lined by ependymal cells ➢ 150-250 ml 29 Cerebrospinal fluid http://www.control.tfe.umu.se PCh AG • Clear fluidproduced by active secretion • Liquor space ➢ lined by ependymal cells ➢ 150-250 ml • Production ✓ Plexus choroideus (PCh) -70% ✓ Cell metabolism ✓ Cappilary filtration ➢ 450-750 ml/day • Resorbtion ✓ Archnoid granulations (AG) 30 Cerebrospinal fluid http://www.control.tfe.umu.se PCh AG• Content ✓ High levels of Mg+ and Na+ ✓ Low levels of K+ and Ca2+ ✓ Almost no cells (max 5/ml) 31 Cerebrospinal fluid http://www.control.tfe.umu.se PCh AG• Content ✓ High levels of Mg+ and Na+ ✓ Low levels of K+ and Ca2+ ✓ Almost no cells (max 5/ml) • Function ✓ Protection ✓ Microenvironment of neurons and glia – Metabolic function – Immunologic function – Transport function and so on 32 New insight into the production and resorbtion of CSF • CSF – cerebrospinal fluid • ISF – interstitial fluid • VRS – Virchow Robin space (space between the pia mater and an artery or a vein, but not capillaries) Ducros A, Biousse V. Headache arising from idiopathic changes in CSF pressure. The Neurology. 2015;14:655–668. 33 Hematoencephalic barrier • Highly organised structure – Endothelial cells (low permeability thanks to zonlua occludens) – Lamina basalis – Astrocytes https://upload.wikimedia.org/wikipedia/commons/1/12/Blood_vessels_brain_english.jpg 34 Hematoencephalic barrier FSM (basic artwork: wikimedia commons) 35 Circumventricular organs • Rich vascularisation • Modified hematoencephalic barrier • Sensors • Secretion http://www.neuros.org/index.php?option=com_photos&view=photos&oid=hafizbilal 36 Intracranial compartment • Brain • Cerebrospinal fluid • Blood (intravasculary) • Intracranial pressure (ICP) • Cerebral perfusion pressure (CPP) pressure gradient driving blood flow intracranialy http://edutoolanatomy.wikispaces.com CPP = MAP - ICPCPP = MAP - ICP Cerebral perfusion pressure Mean arterial pressure Intracranial pressure 37