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CHAPTER 3 BASIC NEUROANATOMY AND CRANIAL NERVES Nervous Tissue 66 Central Nervous System 68 Peripheral Nervous System 72 Cranial Nerves 74 Clinical Correlates 103 3 Nervous Tissue GENERAL INFORMATION Nervous tissue is divided into 2 major cell types: ● Neurons ● Neuroglial cells (the neuroglia) NEURONS The structural and functional cells in the nervous system Respond to a nervous stimulus and conduct the stimulus along the length of the cell A neuron’s cell body is called the perikaryon, or soma Cell bodies are classified by their location: ● Ganglion—a collection of nerve cell bodies located in the peripheral nervous system (e.g., dorsal root ganglion, trigeminal ganglion, ciliary ganglion) ● Nucleus—a collection of nerve cell bodies located in the central nervous system (e.g., Edinger-Westphal nucleus, chief sensory nucleus of cranial nerve V, motor nucleus of cranial nerve VII) Neuron’s cell bodies contain typical cellular organelles within their cytoplasm: ● Mitochondria ● Nucleus ● Nucleolus ● Ribosomes ● Rough endoplasmic reticulum (Nissl substance) ● Neurotubules ● Golgi apparatus ● Lysosomes Neurons have 2 types of processes that extend from the nerve cell body: ● Dendrite—process that carries nerve impulses toward the nerve cell body; neurons may have multiple dendrites ● Axon—process that carries nerve impulses away from the nerve cell body; neurons can have only 1 axon 3 major types of neurons: ● Unipolar—has only 1 process from the cell body (sensory neurons) ● Bipolar—has 2 processes from the cell body: 1 dendrite and 1 axon (sensory neurons; located only in the retina, olfactory epithelium, and the vestibular and cochlear ganglia) ● Multipolar—has 3 or more processes from the cell body: 2 or more dendrites and 1 axon (motor neurons and interneurons) Dendrites Bipolar cell of cranial n. VIII Rough endoplasmic Dendritic spines Unipolar cell of reticulum (gemmules) Interneurons (Nissl substance) sensory ganglia Ribosomes Satellite cells Blood vessel Schwann cell Nucleus Myelinated fibers Nucleolus Axon Free nerve endings Axon hillock Multipolar neuron Encapsulated ending Specialized ending Neurotubules Golgi apparatus Oligodendrocyte Muscle spindle Cell body (soma) Multipolar somatic motor cell Lysosome Astrocyte Mitochondrion Collateral Myelinated somatic motor fiber Myelin sheath Red: Motor neuron Blue: Sensory neuron Purple: Interneuron Gray: Glial and Motor end Striated (voluntary) muscle neurilemmal plate with cells and myelin Schwann cell cap 66 NETTER’S HEAD AND NECK ANATOMY FOR DENTISTRY Nervous Tissue 3 NEUROGLIA Neuroglia is the supporting nervous tissue for neurons, although neuroglial cells also have assistive roles in neuron function Neuroglial cells have only 1 type of process Classification: ● Astrocytes—located in the central nervous system; help keep neurons in place, provide nutritional support, regulate the extracellular matrix, form part of the blood-brain barrier ● Oligodendrocytes—located in the central nervous system; responsible for axon myelination in the central nervous system; 1 oligodendrocyte can myelinate 1 segment of multiple axons ● Microglia—located in the central nervous system; responsible for phagocytosis to remove waste ● Schwann cells—located in the peripheral nervous system; responsible for axon myelination in the peripheral nervous system; 1 schwann cell can myelinate 1 segment of 1 axon ● Satellite cells—located in the peripheral nervous system; surround the nerve cell bodies of ganglia Ventricle Microglial Ependyma cell Tanycyte Neuron Oligodendrocyte Axon Astrocyte Astrocyte foot process Perivascular pericyte Pia mater Capillary BASIC NEUROANATOMY AND CRANIAL NERVES 67 3 Central Nervous System GENERAL INFORMATION The central nervous system is composed of the: ● Brain ● Spinal cord Precentral gyrus Precentral sulcus Central sulcus Postcentral gyrus Superior frontal gyrus Superior parietal lobule Intraparietal sulcus Inferior parietal Middle frontal gyrus lobule Angular gyrus Inferior frontal gyrus Frontal pole Occipital pole Anterior ramus Lateral (sylvian) fissure Ascending ramus Inferior temporal gyrus Posterior ramus Temporal pole Superior temporal gyrus Parietal lobe Frontal lobe Occipital lobe Temporal lobe Central sulcus of insula Circular sulcus of insula Short gyri Insula Limen Long gyrus 68 NETTER’S HEAD AND NECK ANATOMY FOR DENTISTRY Central Nervous System 3 BRAIN CEREBRUM The surface of the cerebral cortex of the brain is divided by: ● Gyri (singular gyrus)—the elevations of brain tissue on the surface ● Sulci (singular sulcus)—the grooves or fissures located between the gyri There are 3 large sulci that help divide the cerebral hemispheres into 4 of its lobes: ● Central sulcus (of Rolando)—divides frontal lobe from parietal lobe ● Lateral sulcus (of Sylvius)—divides the frontal and parietal lobes from the temporal lobe ● Parieto-occipital sulcus—divides the parietal lobe from the occipital lobe The brain is divided into 5 lobes: ● Frontal—motor movement, motor aspect of speech (Broca’s area), reasoning, emotions, personality, and problem solving ● Parietal—sensory perceptions related to pain, temperature, touch and pressure, spatial orientation and perception, sensory aspect of language (Wernicke’s area) ● Temporal—auditory perceptions, learning, and memory ● Occipital—vision ● Insula—associated with visceral functions including taste DIENCEPHALON Composed of 4 parts: ● Thalamus—major relay center of the somatosensory system and parts of the motor system ● Hypothalamus—controls the autonomic nervous system and endocrine system ● Epithalamus—major structures include the pineal gland (which controls circadian rhythms) and the habenula ● Subthalamus—an extrapyramidal nucleus of the motor system; if lesioned, will result in a contralateral hemiballismus BRAINSTEM Composed of 3 parts: ● Midbrain ● Pons ● Medulla CEREBELLUM Part of the motor system Receives sensory input of all forms that use the deep cerebellar nuclei Associated with: ● Equilibrium ● Posture ● Tone of axial muscles ● Gait Corpus callosum Interthalamic adhesion Cuneus Thalamus Hypothalamic sulcus Lingual gyrus Optic chiasm AP Pineal gland Cerebellum Pituitary gland (anterior and posterior) Midbrain Pons Medulla oblongata BASIC NEUROANATOMY AND CRANIAL NERVES 69 3 Central Nervous System SPINAL CORD The caudal continuation of the central nervous system Begins at the caudal end of the medulla and ends at vertebral level L1–2, tapering into the conus medullaris Has 2 enlargements associated with the limbs: ● Cervical—associated with the upper limb and found between the spinal cord at levels C4 to T1 ● Lumbosacral—associated with the lower limb and found between the spinal cord at levels L1 to S2 Composed of: ● Gray matter—location of nerve cell bodies and neuroglial cells ● White matter—location of the axons and neuroglial cells Has 5 levels: ● Cervical—8 spinal nerves ● Thoracic—12 spinal nerves ● Lumbar—5 spinal nerves ● Sacral—5 spinal nerves ● Coccygeal—1 spinal nerve C1 1st cervical n. Cervical enlargement C7 8th cervical n. T1 1st thoracic n. Spinal dura mater Filaments of nerve root T12 Lumbosacral enlargement 12th thoracic n. L1 1st lumbar n. Conus medullaris Cauda equina L5 5th lumbar n. S1 1st sacral n. Filum terminale 5th sacral n. Coccygeal n. Coccyx 70 NETTER’S HEAD AND NECK ANATOMY FOR DENTISTRY Central Nervous System 3 SPINAL CORD CONTINUED Posterior view Rami communicantes Dura mater Dorsal root Dorsal root (spinal) ganglion Arachnoid Subarachnoid space Pia mater (overlying spinal cord) Filaments of dorsal root Denticulate ligament Anterior view Gray matter Filaments of dorsal root White matter Dorsal root Dorsal root (spinal) ganglion Ventral root Spinal nerve Filaments of ventral root Anterior median fissure Sections through spinal cord at various levels C5 T2 T8 L1 L3 S1 S3 BASIC NEUROANATOMY AND CRANIAL NERVES 71 3 Peripheral Nervous System GENERAL INFORMATION Peripheral nervous system is that portion of the nervous system located external to the central nervous system Consists of: ● Cranial nerves—12 pairs ● Spinal nerves—31 pairs Can be subdivided into: ● Somatic nervous system—voluntary system associated with afferent (sensory) and efferent (motor) fibers ● Autonomic nervous system—involuntary system associated with homeostasis of the body Sensory Motor Preganglionic sympathetic Postganglionic Dorsal Dorsal sympathetic column root Pacinian corpuscle Dorsal root ganglion Vascular smooth muscle, sweat glands, and Dorsal arrector pili ramus muscles in skin Skeletal muscle Ventral ramus Gray ramus communicans Ventral root Sympathetic chain ganglion Free White ramus endings Splanchnic nerve communicans Sympathetic chain Collateral sympathetic ganglion Preganglionic sympathetic neurons Skeletal passing to synapse in another muscle sympathetic chain ganglion Neuroeffector junctions on smooth Sensory neuron of muscle, cardiac muscle, secretory abdominal viscera glands, metabolic cells, immune cells 72 NETTER’S HEAD AND NECK ANATOMY FOR DENTISTRY Peripheral Nervous System 3 SPINAL NERVES AND CRANIAL NERVES Oculomotor (III) n. Facial (VII) n. Intracranial vessels Glossopharyngeal (IX) n. Eye Ciliary ganglion Medulla oblongata Lacrimal gland Vagus (X) n. Pterygopalatine Parotid gland C1 ganglion C2 Otic ganglion Sublingual and C3 submandibular glands C4 Submandibular Peripheral cranial C5 ganglion Gray blood vessels C6 Larynx C7 C8 Trachea Bronchi and lungs Sweat T1 gland T2 T3 Heart T4 Greater Celiac thoracic ganglion Shown Peripheral T5 splanchnic n. vessel Stomach for only T6 1 segment Liver T7 c n. Gallbladder T8 Bile ducts Lesser thoracic splanchni T9 Rami communicantes gray and white Pancreas Sup. mesenteric Hair T10 ganglion Adrenal glands follicle Brown fat T11 Lowest thoracic splanchnic n. Kidneys T12 L1 Lumbar Intestines L2 splanchnic nn. L3 Lymphoid organs Sup. Inf. L4 hypogastric mesenteric Gray plexus ganglion Distal colon L5 Hypogastric S1 nn. Bladder S2 S3 Pelvic splanchnic nn. S4 S5 Sympathetic External genitalia Coccyx Inf. hypogastric trunk (pelvic) plexus Sympathetic fibers Parasympathetic fibers preganglionic preganglionic postganglionic postganglionic BASIC NEUROANATOMY AND CRANIAL NERVES 73.
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  • Canine Dorsal Root Ganglia Satellite Glial Cells Represent an Exceptional Cell Population with Astrocytic and Oligodendrocytic P

    Canine Dorsal Root Ganglia Satellite Glial Cells Represent an Exceptional Cell Population with Astrocytic and Oligodendrocytic P

    www.nature.com/scientificreports OPEN Canine dorsal root ganglia satellite glial cells represent an exceptional cell population with astrocytic and Received: 17 August 2017 Accepted: 6 October 2017 oligodendrocytic properties Published: xx xx xxxx W. Tongtako1,2, A. Lehmbecker1, Y. Wang1,2, K. Hahn1,2, W. Baumgärtner1,2 & I. Gerhauser 1 Dogs can be used as a translational animal model to close the gap between basic discoveries in rodents and clinical trials in humans. The present study compared the species-specifc properties of satellite glial cells (SGCs) of canine and murine dorsal root ganglia (DRG) in situ and in vitro using light microscopy, electron microscopy, and immunostainings. The in situ expression of CNPase, GFAP, and glutamine synthetase (GS) has also been investigated in simian SGCs. In situ, most canine SGCs (>80%) expressed the neural progenitor cell markers nestin and Sox2. CNPase and GFAP were found in most canine and simian but not murine SGCs. GS was detected in 94% of simian and 71% of murine SGCs, whereas only 44% of canine SGCs expressed GS. In vitro, most canine (>84%) and murine (>96%) SGCs expressed CNPase, whereas GFAP expression was diferentially afected by culture conditions and varied between 10% and 40%. However, GFAP expression was induced by bone morphogenetic protein 4 in SGCs of both species. Interestingly, canine SGCs also stimulated neurite formation of DRG neurons. These fndings indicate that SGCs represent an exceptional, intermediate glial cell population with phenotypical characteristics of oligodendrocytes and astrocytes and might possess intrinsic regenerative capabilities in vivo. Since the discovery of glial cells over a century ago, substantial progress has been made in understanding the origin, development, and function of the diferent types of glial cells in the central nervous system (CNS) and peripheral nervous system (PNS)1.