Nervous Tissue Topic 13 PDF

TOPIC 13. NERVOUS TISSUE The body's internet! Exploring the communication network of the nervous tissue. Riánsares Arriazu Navarro, PhD Learning objectives Describe the...

TOPIC 13. NERVOUS TISSUE The body's internet! Exploring the communication network of the nervous tissue. Riánsares Arriazu Navarro, PhD Learning objectives Describe the general characteristics of nerve tissue. Know, describe and identify the components of nervous tissue. Know how to identify the organs of the CNS from a histological point of view. Know how to identify the organs of the PNS from a histological point of view. Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 1 TOPIC 13. NERVOUS TISSUE Chapter outline Introduction Divisions of the nervous system Components of nervous tissue Nerve fibres Organisation of nerve tissue in the CNS Organisation of nerve tissue in the PNS Riánsares Arriazu Navarro, PhD INTRODUCTION Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 2 TOPIC 13. NERVOUS TISSUE INTRODUCTION Tissue: a group of closely associated cells that perform related functions and are similar in structure Four basic types of tissue: Epithelial tissue: Connective tissue: Muscle tissue: Nervous tissue: Covering, secretion support movement control Riánsares Arriazu Navarro, PhD NERVOUS TISSUE Origin: ectoderm Controls and integrates all body activities within limits that maintain life Gets the message Interpretation Response (sensory) (integration) (motor) Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 3 TOPIC 13. NERVOUS TISSUE DIVISIONS OF THE NERVOUS SYSTEM Riánsares Arriazu Navarro, PhD Nervous system Peripheral NS Central NS (CNS) (PNS) Brain Spinal cord Somatic NS Autonomic NS Parasympathetic Sympathetic NS NS Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 4 TOPIC 13. NERVOUS TISSUE GENERAL ORGANIZATION Astrocytes Anatomy: Histology: Oligodendrocytes Brain Neurons Microglial cells CNS Ependymal cells Spinal cord Neuroglial cells Anatomy: Histology: Satellite cells PNS Cranial, spinal Neurons Schwann cells and peripheral Neuroglial nerves cells Ganglia Motor and sensory nerve endings Riánsares Arriazu Navarro, PhD COMPONENTS OF NERVOUS TISSUE Neurons Neuroglial cells Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 5 TOPIC 13. NERVOUS TISSUE NEURONS OR NERVE CELLS Structural unit of nervous tissue. Conduct messages in the form of nerve impulses from one part of the body to another Characteristics: Extreme longevity Amitotic High metabolic rate (O2 y Glucose) Structure: Cell body, perikaryon or soma Processes or neurites Riánsares Arriazu Navarro, PhD Plasma membrane: CELL BODY Receives stimuli, integrates them and generates the response (nerve impulse) Ion channels Na+-K+ pump Metabolic center of the cell Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 6 TOPIC 13. NERVOUS TISSUE Plasma membrane: CELL BODY Cytoplasm: – Nissl’s granules (rER) – Golgi apparatus – Cytoskeleton or neurofibrils – Cytoplasmic inclusions Riánsares Arriazu Navarro, PhD Plasma membrane: CELL BODY Cytoplasm: Nucleus: Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 7 TOPIC 13. NERVOUS TISSUE PROCESSES OR NEURITES Dendrite: 0-X Short branched extension which receive stimuli from other nerve cells Axon: One Long extension which transmit impulses to other neurons or effector cells Riánsares Arriazu Navarro, PhD DENDRITES Many dendrites Non-myelinated Short No vesicles containing Irregular neurotransmitters Branched Nissl’s granules Spines Diameter decreases Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 8 TOPIC 13. NERVOUS TISSUE AXON ONE Lomg Arises from a conical projection (axon hillock) Uniform diameter Branched at their ends Tips of the terminal branches are enlarged to form synaptic knobs or axon terminals Synaptic knobs: vesicles with neurotransmitters With or without myeline No Nissl’s granules Riánsares Arriazu Navarro, PhD Generate and transmit action potentials Secrete neurotransmitters from the synaptic knobs Transport AXON Secretion Movement along axons occurs in two ways: Anterograde Kinesin Retrograde Dynein Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 9 TOPIC 13. NERVOUS TISSUE CLASSIFICATION OF NEURON According to their function According to the number of processes Riánsares Arriazu Navarro, PhD According to their function SNC E  RECEPTOR    MUSCLE Sensory (afferent) neurons: Interneurons: – Only in CNS Motor (efferent) neurons:  Transmit sensory information – Transmit motor  – Interconnectors or integrators between information Transmit impulses toward the CNS sensory and motor – Transmit information neurons  from the CNS to effectors cells (muscles, glands, etc) Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 10 TOPIC 13. NERVOUS TISSUE According to the number of processes Riánsares Arriazu Navarro, PhD SYNAPSES Functional connection between nerve fiber and target cell Types: Unidirectional transmition: Consisting of: Presynaptic cell (neuron) Synaptic cleft Postsynaptic cell (neuron, myocyte, gland…) Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 11 TOPIC 13. NERVOUS TISSUE NEUROGLIAL CELLS 10 times more neuroglial cells than neurons. 50% of nervous system weight Undergo mitosis GAP junctions They do not react to or propagate nerve impulse Functions: − Support, nourish and protect neurons Riánsares Arriazu Navarro, PhD ASTROCYTES Stellate cells displaying abundant cytoplasm: Intermediate filaments: GFAP A large nucleus Many short branching processes: The tips of some end as pedicels (vascular feed): in contact with blood vessels Near the brain or surface of the spinal cord exhibit pedicel-tipped processes that contact the pia mater Some processes in contact with neurons Functions: Assist in maintaining the blood-brain barrier Regulates tissue fluid composition Provides structural support and organization to CNS Stimulate the formation of scar tissue secondary to CNS injury Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 12 TOPIC 13. NERVOUS TISSUE OLIGODENDROCYTES Compared with astrocytes: Smaller Fewer processes with sparce branching Functions: Active in the formation and maintenance of myelin in the CNS Riánsares Arriazu Navarro, PhD MICROGLIA Thorny bushes in appearance and the smallest glia Non-activated Originate from monocytes Phagocytic function in CNS: Defense against pathogens Remove debris Phagocyte wastes Activated Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 13 TOPIC 13. NERVOUS TISSUE EPENDYMAL CELL Low columnar to cuboidal epithelial cells In some regions they are ciliated Functions: Lines the ventricles of the brain and central canal of the spinal cord Formation of cerebrospinal fluid and facilitates its movement Riánsares Arriazu Navarro, PhD Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Capillary Neurons Astrocyte Oligodendrocyte Perivascular feet Myelinated axon Ependymal cell Myelin (cut) Cerebrospinal fluid Microglia Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 14 TOPIC 13. NERVOUS TISSUE SATELLITE CELLS Small round or spindle-shaped cells Located in ganglia around the cell bodies Functions: Protect cells bodies Regulate nutrients for cell bodies Riánsares Arriazu Navarro, PhD SCHWANN CELLS Flattened cells covered by a basal membrane Cytoplasm: Flattened nucleus Small Golgi apparatus Few mitochondria They envelop axons Functions: Myelinates and insulates PNS axons Allows for faster nerve impulse conduction through the axon Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 15 TOPIC 13. NERVOUS TISSUE NERVE FIBRES Myelin and myelination Myelinated nerve fibres Unmyelinated nerve fibres Riánsares Arriazu Navarro, PhD MYELIN SHEATH Composed of phospholipids, glycolipids and cholesterol Whitish segmented sheath around most long axons Functions: Protect the axon Electrically insulate fibers from one another Increase the speed of nerve impulse transmission Cells that synthesize myelin: CNS: oligodendrocytes PNS: Schwann cells Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 16 TOPIC 13. NERVOUS TISSUE MYELINATION Myelination: process of myelin formation:  Invagination of a single nerve axon into a Schwann cell  Plasma mb surrounds the axon and joins to form a double-mb structure that communicates with the cell surface (mesaxon) Mesaxon rotates around the axon enveloping the axon in concentric layers  Axon and the cytoplasmic surfaces condense into a compact myelin sheath  Mesoaxon s Riánsare     Riánsares Arriazu Navarro, PhD Schmidt-Lanterman incisures Axon s Riánsare Node of Ranvier Intermode: myelin between nodes Neuroglial Nerve Axon cells fiber Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 17 TOPIC 13. NERVOUS TISSUE Riánsares Arriazu Navarro, PhD Myelinated fiber Nerve Unmyelinated fiber fiber R Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 18 TOPIC 13. NERVOUS TISSUE ORGANISATION OF NERVOUS TISSUE IN THE CNS Spinal cord Cerebellum Riánsares Arriazu Navarro, PhD GENERAL INFORMATION Grey matter: Mostly soma, dendrites, glial cells and unmyelinated fibers White matter: Myelinated fibers Axons, dendrites, and neuroglial processes form a tangled network of neural tissue called neuropil Meninges: connective tissue Dura mater (2 layers) Arachnoid mater Leptomeninges or pia-arachnoid Pia mater Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 19 TOPIC 13. NERVOUS TISSUE Riánsares Arriazu Navarro, PhD Spinal Cord Connetive tissue Ventral horns: motor (meninges) neurons 1: Ventral horns 3 1 2: Dorsal horns Dorsal horns: sensory 3: Lateral horns neurons Central canal 2 3 White matter Grey matter Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 20 TOPIC 13. NERVOUS TISSUE Dorsal horns: sensory neurons Ventral horns: motor neurons Riánsares Arriazu Navarro, PhD Cerebelum Grey matter = cortex White matter = medulla Blue = myelin Medulla = White matter Pink = neuropil Cortex = Grey matter Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 21 TOPIC 13. NERVOUS TISSUE Cerebelum Cortex Medulla Oligodendrocytes Molecular Layer Purkinje Cells Myelinated Granular fibers Layer Riánsares Arriazu Navarro, PhD ORGANISATION OF THE NERVOUS TISSUE IN THE PNS Nerves Ganglia Sensory receptors Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 22 TOPIC 13. NERVOUS TISSUE PERIPHERAL NERVES nerve fibers together into elongated bundles: Fascicles Epineurium Perineurium Endoneurium Riánsares Arriazu Navarro, PhD Cross section Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 23 TOPIC 13. NERVOUS TISSUE Longitudinal section. Small peripheral nerves Riánsares Arriazu Navarro, PhD Peripheral nerve regeneration A: Normal motor neuron B: Injury. Chromatolysis C: Atrophy. Scarring D: Successful regeneration E: Unsatisfactory regeneration Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 24 TOPIC 13. NERVOUS TISSUE GANGLIA Autonomic ganglia Sensory ganglium Sympathetic ganglium Parasympathetic ganglium Associated with craneal Are found adjacent to Are found within or near nerves the vertebral column the effector organs Pseudounipolar cell bodies Multipolares neurons Multipolares neurons and of the sensory nerves and satellite cells satellite cells enveloped by satellite cells Riánsares Arriazu Navarro, PhD SENSORY RECEPTORS All information about the world is gathered through the five senses: Stimuli are detected by receptors Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 25 TOPIC 13. NERVOUS TISSUE SENSORY RECEPTORS ACCORDING TO THE STIMULUS ACCORDING TO THE MEDIUM FROM TYPE WHICH THE STIMULUS COMES Mechanoreceptors: mechanical Exteroceptors: outer pressure and vibrations (touch and hearing) environment Thermoreceptors: temperature (skin) Interoceptors: corporal Nociceptors: pain internal medium Photoreceptors: light (vision) Chemoreceptors: chemical stimuli Proprioceptors: SkM, (smell and taste) tendons, joints and ligaments Riánsares Arriazu Navarro, PhD VISION Light bounces off of an object The light travels through the cornea Focused light hits photereceptors (rod and cone cells) Electric signal travel We see the object Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 26 TOPIC 13. NERVOUS TISSUE HEARING Sound waves travel through the air and are detected by auditory receptors. Outer ear Middle ear crista Mechanoreceptors: ampularis Sound endolymph macula Balance of utricle Middle ear The ear is also important for balance. vestibule (perilymph) Riánsares Arriazu Navarro, PhD U-M Histology Collection SMELL Olfactory Epithelium: Olfactory cells: chemoreceptors Sustentacular cells Basal cells Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 27 TOPIC 13. NERVOUS TISSUE TASTE Chemoreceptors Lingual papillae Tongue Taste buds Nerve ending Taste sensory Taste pore cell Riánsares Arriazu Navarro, PhD TOUCH: SKIN Mechanoreceptors: Touch Meissner corpuscles Pacinian corpuscles Thermoreceptors: Temperature Krause corpuscles (loss of heat) Ruffini corpuscles (heat input) Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 28 TOPIC 13. NERVOUS TISSUE Riánsares Arriazu Navarro, PhD Riánsares Arriazu Navarro, PhD ([email protected]) 29