Histology of the Nervous System – Part 1, Summer 2024 PDF

HISTOLOGY OF THE NERVOUS SYSTEM – PART 1 S 2024 María José Navarrete Talloni, DVM, MPVM, PhD...

HISTOLOGY OF THE NERVOUS SYSTEM – PART 1 S 2024 María José Navarrete Talloni, DVM, MPVM, PhD Department of Biomedical Sciences, RUSVM Disclaimer: Images and information in this presentation come from different sources including Drs. I. Irimescu, O. Illanes, M. Smith, M. Zibrin, P. Hanna and H. Bogdanovic‘s notes. Dellmann’s and Junqueira’s histology books, P. Hyttel et al. and K. Moore embryology books. This presentation is for teaching purposes only, please do not distribute. Part 1 Outline Nervous system – Overview Meninges Brain structures & surface features Nervous tissue White & Grey matter Neurons Glial cells (in CSN) Oligodendrocytes Microglial cells Astrocytes Nervous System Overview Nervous System Central nervous Peripheral nervous system (CNS) system (PNS) Brain Spinal cord Autonomic nervous Somatic system (ANS) nervous system Parasympathetic division Sympathetic division Meninges Scalp skin Skull bone Subarachnoid space Meninges The brain and spinal cord and the roots of peripheral nerves are enveloped by a series of connective tissue sheaths. Dura mater — outermost layer (Pachymeninx, Gr. pachys – thick) Arachnoid — membrane attached to dura mater Pia mater — highly vascular, adherent to brain and spinal cord Leptomeninges – Arachnoid + Pia mater Subarachnoid space — contains Cerebrospinal Fluid (CSF) Meningeal Layers Gray’s Anatomy FYI New meninges SLYM Subarachnoidal Lymphatic-like Membrane. - In mice and humans - Separates “clean” and “dirty” cerebrospinal fluid. SLYM and immunity The SLYM appeared to contain large numbers of myeloid cells, including white blood cells and macrophages. As a result, the SLYM may be well-positioned to have an immune monitoring role.  Brain The five brain divisions are convenient for CR CD regionally categorizing the locations of brain components. http://vanat.cvm.umn.edu/neurLab3/pages/MedFiveDiv.html EMBRYONIC BRAIN DERIVED BRAIN STRUCTURES DIVISION FOREBRAIN Telencephalon Cerebrum, Basal Nuclei, Hippocampus and Amygdala Diencephalon Thalamus and Hypothalamus MIDBRAIN Mesencephalon Midbrain HINDBRAIN Metencephalon Pons & Cerebellum Myelencephalon Medulla oblongata  entirely Brain thething Suvas Cerebral cortex Sulcus (pl. sulci) is WS son GyrusSulcus short Fissure Gyrus (pl. gyri) Cerebellar cortex  SULCI SULCUS GYRI GYRUS  Spinal Cord o The canine spine comprises 31 segments of interest; 8 cervical segments, 13 thoracic segments, 7 lumbar and 3 sacral, each of which supplies a lower sensory and motor spinal nerve. The spine can be functionally divided into 5 areas (Figure 5): a corresponds to segments C1-C5, b C6- T2, c T3-L3, d L4-S1 and e S1-S3. https://vetgrad.com/show10MinuteTopUp.php?type=Small&Entity=10MinuteTopUps&ID=21 Spinal Cord  Nervous Tissue Neurons do Astrocytes Nervous tissue CNS Oligodendroglia Microglial cells Neuroglia (Glial cells) Ependymal cells Schwann cells PNS Satellite cells  White & Grey Matter When the CNS (brain, spinal cord) is examined grossly grey matter and white matter regions can be observed. White matter - formed by dense accumulations of myelinated axons. The myelin sheath is rich in lipids and has a white appearance. Grey matter - rich in neuronal cell bodies, glial cells and neuropil. The neuropil represents the axons, dendrites and cytoplasmic projections of glial cells that form the background matrix to neuronal cell bodies within the grey matter. Grey matter (neurons, glia) White matter (axons, glia) Gross Image: Cow’s brain, coronal section – Arauz/ Illanes. Cerebrum - Brain Luxol Fast Blue stain to highlight myelin. http://vanat.cvm.umn.edu/brainsect/  Grey matter (neurons, glia) Cerebellum 0 Spinal cord White matter (axons, glia) White matter contains Grey matter contains neurons, myelinated axons and glial cells, glial cells, and axons, blood blood vessels vessels White matter is peripheral in Grey matter position is spinal cord, central in the brain peripheral in brain, central in spinal cord  Cellular composition of the central nervous system (CNS) Ectodermal Origin (very sensitive to hypoxia) Neurons onestodie Diedxythveiswtoef.us Astrocytes Oligodendrocytes Mesodermal Origin (not as sensitive to hypoxia) Microglia Vascular endothelium  Cellular composition of the central nervous system (CNS) Neurons Glial cells (neuroglia = “neural glue”) Ependymal cells Endothelial cells Pericytes of blood vessels http://slideplayer.es/slide/5611337/2/images/1/NEUROGLIA.jpg  Neurons http://learnwise.co/wp-content/uploads/2018/09/labelled-neuron-diagram-inspirational-what-are-the-parts-of-the-neuron-and-their-function-quora.png The neurons are the functional cells of the nervous system in which two protoplasmic properties are highly developed: irritability (generation of an impulse) and conductivity (ability to transmit such an impulse from one locality to another). Neurons are dispersed throughout the CNS and grouped in specific areas in PNS.  Neurons havethis Everyone Cell body = Perikaryon / Soma Parts: The cell body of the neuron contains the Perikaryon nucleus and the organelles. The axon and Nucleus Nucleolus the dendrites branch off off the cell body. Dendrites Axon  Neuron – Soma Structure o Euchromatic nucleus with prominent nucleolus o Basophilic cytoplasm = Nissl substance: RER and ribosomes brownpigman o They are long-living cells ageing pigment = Lipofuscin accumulation  From McGavin: Path Basis of Disease Neurons & Glial cells. Ventral grey horn of SC, horse. Neuron distribution Individually Layers (cortex) Groups: Nuclei (CNS) samfuatyofw.ms fresaegrap Ganglia (PNS) San feet  FYI - Synapses Specialized junctions with Synapses at end of an other cells that are along axon or axon branches the length or at end of an are swollen into a club axon. shape, called boutons Act as transmission points terminaux. for electrical impulses. Those along length of Can trigger the generation axon result of an action potential in in varicosities (swellings) the postsynaptic cell; they in the axon, can be excitatory or called boutons en inhibitory. passant. FYI - Structure of Synaptic Knobs Each nerve synapse consists of 3 parts: A.Presynaptic part – termination of axon (Bouton terminaux) B.Intersynaptic cleft C.Postsynaptic part (Dendritic thorn) Presynaptic part SYNAPTIC VESICLES contain different types of neurotransmitters (acetylcholine, noradrenaline and A C adrenaline [aka norepinephrine and epinephrine], GABA, Dopamine, etc.) B Presynaptic part Postsynaptic part FYI - Synapses in TEM Synaptic knob Synaptic knob Synaptic vesicles endrite Postsynaptic membrane endrite Stimulatory synapse. Synaptic Inhibitory synapse. Synaptic vesicles contain acetylcholine oval vesicles contain GABA www.exploringnature.org/graphics/anatomy/sense_organs  Pacinian corpuscle (400x) Afferent ending Capsule Female urethra  Oligodendrocytes Functions: Provide support and the myelin sheath to axons within the CNS. Ooligodendrocytes form myelin sheaths for several axons at once (“octopus” shape) difference with Schwann cells (PNS) http://blustein.tripod.com/Oligodendrocytes/oligodendrocytes.htm 0  Oligodendrocytes Small dark nuclei (between myelin sheaths or around neurons). Can be destroyed by viruses/toxins resulting in primary demyelination. Silver stain  Microglia Functions: Immunosurveillance Immunoregulation Reparative phagocytic Gitter cells (myelophages) are microglial cells that are activated during necrosis or inflammation globular and swollen after having phagocytized debris from injured cells https://media.nature.com/m685/nature-assets/nm/journal/v12/n8/images/nm0806-885-F1.jpg  Microglia Derived from blood-borne monocyte Resident macrophage of CNS Gitter Cells note the cytoplasmic vacuolation due to ingestion of cellular debris B. SUMMERS  Microglia Activated macrophages (Gitter cells) in an area of brain tissue necrosis  Microglia O O Activated microglial cells in a myelin sheath (“myelophages” with a “digestion chamber”).  Astrocytes CNS counterpart of the fibroblast. Involved in cell communication and the functioning of the blood brain barrier (BBB). Two types Protoplasmic (grey matter) Fibrillar (white matter) Glial fibrillary acidic protein (GFAP) staining IHC (GFAP) stain  Astrocytes Functions: Transport of nutrients Part of blood brain barrier Antigen presentation Blood Brain Barrier