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histologic nervous system, neuron, neuroglial, axon, dendrite, brain, spinal cord, blood-brain barrier

histologic nervous system, neuron, neuroglial, axon, dendrite, brain, spinal cord, blood-brain barrier

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    histologic structure of nervous system histologic structure of nervous system Presentation Transcript

    • HISTOLOGY OF NERVOUS SYSTEM DR. I WAYAN SUGIRITAMA,M.Kes HISTOLOGY DEPARTMENT MEDICAL FACULTY OF UDAYANA UNIVERSITY
    • NERVOUS SYSTEM
      • The most complex system in the human body
      • Formed by network more than 100 million neuron
      • Each neuron has a thousand interconnection  a very complex system for communication
      • Nerve tissue is distribute throughout the body, anatomically divide into : CNS & PNS
      • Structurally consist : nerve cells & glial cells
      23/06/09
    • CONTENTS
      • Cells of nervous system
      • Synaptic communication
      • Central nervous system & Peripheral nervous system & associated structure
      • Regeneration of nervous system
      23/06/09
    • REFFERENCES
      • Color Textbook Histology, third edition, leslie P. Gartner
      • Basic Histology, tenth edition, L. Carlos Junqueira,2003
      • Histology and Cell Biology, second edition,2007
      • Elsevier’s Integrated Histology,2007
      23/06/09
    • CELLS OF NERVOUS SYSTEM 23/06/09 NEURON NEUROGLIA
    • STRUCTURE OF NEUR ON
      • Principle cells of Nervous Tissue
      • Consist of 3 parts :
        • CELL BODY (perikaryon/soma)
        • A single AXON
        • Multiple DENDRITES
      • ø 5-150 µm
      23/06/09
    • CELL BODY (PERIKARYON)
      • Central portion of the cell
      • Generally are polygonal
      • Different shape and size  characteristic regions of nervous system
      • Contain :
        • Nucleus
        • Perinuclear cytoplasm
      23/06/09
    • ULTRASTRUCTURE OF NEURON
      • Nucle us :
      • large, spherical to ovoid and centraly located
      • a single prominent nucleolus
      • finely dispersed chromatin
      •  trancriptionaly active
      •  
      23/06/09
    • ULTRASTRUCTURE OF NEURON
      • Cytoplasm :
      • A bundant of R.E.R
      • Polyribosomes
      • Basic dyes (a+b)  Nissl Bodies
      • lots of S.E.R.
      • Golgi bodies (perikaryon)
      • protein secreting cell
      23/06/09
    • ULTRASTRUCTURE OF NEURON
      • Cytoplasm
      • M any mitochondria, most abundant in axon terminal
      • extensive cytoskeleton  axonal transport
      • One centriole  do not undergo cell divisions
      23/06/09
    • DENDRITE AND AXON
      • AXON
        • Single process u p to 100 cm
        • Originate from axon hillock
        • Devoid ribosome
        • Dilatation of distal portion  axon terminal  end bulbs  synapse
        • conducting impulse away from the soma
        • Axonal transport
      • DENDRITES
        • Multiple elongated processes
        • Cytoplasmic~perikaryon (devoid golgi complex)
        • Receiving stimuli
      23/06/09
    • NEURONS CLASSIFICATION :
      • According to the size and shape of the processes
      (Dorsal root & cranial nerve ganglia) (Pyramidal & purkinje) 23/06/09
    • NEURONS CLASSIFICATION : 23/06/09
    • NEURONS CLASSIFICATION :
      • According to their function :
      • Sensory Neuron (afferent )
        • Receive sensory input  conduct impulses to CNS
      • Motor Neuron (Efferent)
        • CNS  conduct impulses to muscles, glands and other neurons
      • Interneuron
        • In the CNS as interconnectors, establish neuronal circuit between sensory and motor neuron
      23/06/09
    • NEURON GROUPING
      • CORTEX
        • Neuron form six layers on the cerrebrum
        • Form three layers on the cerrebellum
      • NUCLEI
        • In subcortical region (thalamus, midbrain, brainstem and spinal cord) neuron form irregular cluster  nuclei
      • GANGLION
        • Cluster of neuron outside the CNS
      23/06/09
    • FUNCTION OF NEURON
      • R eceptive
        • Receptor receive stimuli and tranduce into nerve impulse and transferro to other neuron
      • I ntegrative
        • Processing impulse on the higher center
      • M otor
        • Initiating motor respons and tranduse impulse to the effector
      23/06/09
    • SYNAPS ES
      • Sites of impulse transmission
      • Convert electrical signal into chemical signal
      • Permit neurons to communicate
      • Types of synapses :
        • Axodentritic synapse
        • Axosomatic synapse
        • Axoaxonic synapse
        • Dendrodentritic synapse
      23/06/09
    • SYNAPS 23/06/09
    • NEURO GLIAL CELLS
      • Metabolic and mechanical support for neuron
      • 10 times abundant than neurons
      • Neuroglial cells undergo mitosis
      • Classification :
        • Oligodendrocytes
        • Astrocytes
        • Ependymal Cells
        • Microglia
        • Schwan cells 
      CNS PNS 23/06/09
    • NEURO GLIAL CELLS
      • Astrocytes
        • Pedicles binds to capillaries and to the pia mater form glial limitans
        • Controlling the ionic & chemical env ironment of neurons
        • Energy metabolism
        • Form cellular scar tissue
        • Form the blood-brain barrier
      23/06/09
    • NEURO GLIAL CELLS
      • Oligodendrocytes
      • interfascicular
        • Produce myelin sheath (electrical insulation) in CNS
        • A single cell wrap several axons (40 to 50)
        • Form nodes of Ranvier
      • satellite
      23/06/09
    • NEURO GLIAL CELLS
      • Schwann cells
        • Analogue to Oligodendrocyte
        • Produce myelin sheath in the PN S
      23/06/09
    • NEURO GLIAL CELLS
      • Microglia
      • Scattered throughout the CNS
      • Clearing debris
      • Act as APC
      • Protect the CNS from viruses and microorganism
      23/06/09
    • NEURO GLIAL CELLS
      • Ependymal Cells
        • Low columnar ciliated epithelial cells  line the ventricles of the brain & central canal spinal cord
        • Formation of choroid flexus  produce CSF
        • Facilitates the movement of CSF
      23/06/09
    • Anatomically divided in to : 06/23/09 NERVOUS SYSTEM CENTRAL NERVOUS SYSTEM (CNS) PERIPHERAL NERVOUS SYSTEM (PNS)
    • THE CNS
      • Consist of :
        • Cerebrum
        • Cerebellum
        • Spinal cord
      • No connective tissue  soft, gel like
      • When sectioned :
        • White matter
        • Gray matter
      • Covered by meninges
      06/23/09
    • CEREBRUM
      • GRAY MATTER
        • Contains neuronal cell bodies, dendrites and glial cells
        • Six layers composed of neuron
        • Neuron (pyramidal) :
          • Afferent (sensory)
          • Efferent (motor)
      • WHITE MATTER
        • Contains myelinated axons and myelin-producing oligodendrocytes
      23/06/09
    • CEREBELLUM
      • GRAY MATTER
        • Three layers :
          • Outer molecular layer
          • Central layer of large Purkinje cells
          • Inner granule layer
      • WHITE MATTER
          • The same as cerebrum
      23/06/09
    • SPINAL CORD
      • GRAY MATTER (CENTRAL)  SHAPE OF “H”
        • Central canal lined by Ependymal cells
        • Legs of the “H” form :
          • Anterior horns
          • Posterior horns
        • Neurons : large and multipolar
      • WHITE MATTER (PERIPHERAL)
      23/06/09
    • PNS
      • Bundles of nerve fibers (axons) outside the CNS & surrounded by connective tissue
      • Main component :
        • Peripheral nerves
        • Ganglia
        • Nerve endings
      06/23/09
    • NERVE FIBERS
        • Consist of axons enveloped by a special sheath
        • Group of fibers constitute the peripheral nerve
        • Two types :
          • Myelinated fiber
          • Unmyelinated fiber
      23/06/09
    • NERVE FIBERS
      • Myelinated fibers
        • A single Schwann cell wraps around single axon  form myelin sheath  nodes of Ranvier
      • Unmyelinated fibers
        • A single Schwann cell envelopes several axon
        • Fibers enveloped within simple clefts of Schwann cells
      23/06/09
    • MYELINATION PROCESS 23/06/09
    • CONDUCTION VELOCITY
      • Depend on the extent of
      • Myelination :
      • Unmyelinated fibers
        • No nodes of Ranvier  continuous conduction
        • Slower conduction
      • Myelinated fibers
        • Gap of myelin sheath ( nodes of Ranvier )  saltatory conduction
        • Faster conduction
      23/06/09
    • CONNECTIVE TISSUE INVESTMENTS
      • Epineureum
        • Dense collagenous Con. Tissue with thick elastic fiber
        • Prevent damage by overstreching
      • Perineureum
        • Dense con. Tissue
        • Layers of epithelioids
        • Isolates neural environment (blood-nerve barrier)
      • Endoneureum
        • Loose con. Tissue
        • Regulation of microenvironment of nerve fiber
      23/06/09
    • PERIPHERAL NERVE 06/23/09
    • PERIPHERAL NERVE 23/06/09
    • GANGLIA
      • Ovoid structure containing neuronal cell bodies, glial cells supported by connective tissue
      • Function : Relay stations to transmit impulses
      • Types :
        • Sensory ganglia
        • Autonomic ganglia
      23/06/09
    • GANGLI A
        • Sensory Ganglia (cell bodies of sensory neuron)
          • Unipolar cell bodies enveloped by cuboidal capsule cells
            • Cranial ganglia : Associated with the cranial nerve
            • Spinal ganglia : Associated with the spinal nerve
        • Autonomic Ganglia (cell bodies of postganglionic autonomic nerves)
          • Multipolar neuron enveloped by satellite cells
          • Some are located within certain organ (intramural)
      23/06/09
    • DORSAL ROOT GANGLIA 06/23/09
    • FUNCTIONAL CLASSIFICATION OF NERVES
      • Sensory nerve fibers
        • Carry sensory input from the cutaneus/ viscera area  to CNS
      • Motor nerve fibers
        • Originate in the CNS  carry motor impulses to the effector organs
      06/23/09
    • FUNCTIONAL CLASSIFICATION OF MOTOR COMPONENT
      • Somatic nervous system
      • Provide motor impulses to skeletal muscles
      • Cells bodies (multipolar) originate in the motor nuclei of the brain or ventral horn of spinal cord
      • The axon travel to the skeletal muscle via cranial or spinal nerve
      • Autonomic nervous system
      • Provide motor impulses to the smooth muscle of viscera, cardiac muscle, secretory cells
      • HOMEOSTASIS
      06/23/09
    • AUTONOMIC NERVOUS SYSTEM
      • ANS = two-neuron network
      • First Neuron
        • Neuron in CNS
        • Axon (preganglionic fibers) form a synapse with second multipolar neuron in ganglion
      • Second Neuron
        • Neuron in the Ganglion
        • Axon to the effectors (postganglionic fibers)
      23/06/09
    • AUTONOMIC NERVOUS SYSTEM
      • SYMPHATETIC SYSTEM
      • The nuclei located in the thoracic and lumbar segment of spinal cord
      • Preganglionic fibers leave the CNS by way of ventral roots
      • The chemical mediator postganglionic fibers is norepinephrine
      • PARASYMPHATETIC SYSTEM
      • The nuclei located in the medulla and midbrain and in the sacral portion of spinal cord
      • Pre ganglionic fibers leave the CNS trough cranial nerve III, VII, IX and X and also trough II, III, IV sacral nerve
      • The ganglion located near the effector organs
      • The chemical mediator pre and postganglionic fibers is acethilcholine
      06/23/09
    • MENINGES
      • The dura mater
        • dense, collagenous connective tissue
      • The arachnoid layer :
        • fibroblasts, collagen & elastic fibers
        • Layer in contact with dura mater & a system of trabeculae
        • Form arachnoid villi
      • The pia mater
        • Loose con. Tissue with blood vessel
        • There is a physical barrier between pia mater & neuron
      06/23/09
    • BLOOB-BRAIN BARRIER
      • Prevents the passage of
      • substances (bacterial, toxic,
      • Chemical…) from blood to
      • nerve tissue
      • Endothelial of capillary
        • Occluding junction
        • No fenestration
      • Expansions of Astrocytes cell processes that envelope the capillary
      ↓ permeability 23/06/09
    • CHOROID FLEXUS
      • Choroid flexus co nsist of loose conn . tissue of the pia matter, covered by a simple/ low columnar epith .  ion transporting cells
      • Elaborate CSF  fill the ventricles  subarachnoid space (arachnoid villi)  venous
      • CSF function  metabolism and protective of CNS
      23/06/09
    • CEREBROSPINAL FLUID
      • Composition
        • clear,
        • low density & protein content
        • High Na, K, Cl
      • Function
        • Metabolic
        • Liquid cushion
      • Blood-CSF barrier
        • Zonulae occludents
      23/06/09
    • NERVE REGENERATION
      • Diseases affecting Schwann cells  loss of myelin (segmental demylination)
      • Nerve injury  induced axonal degeneration (wallerian degeneration)  followed by regeneration
      • Axon reaction :
        • Local changes
        • Anterograte changes
        • Retrograte changes
      06/23/09
    • Axon reaction
      • Local reaction
        • Severe ends of axon retract & cuts membrane fuses
        • Macrophage & fibroblasts infiltration
      • Anterograde reaction
        • Axon terminal degeneration
        • Schwann cells proliferation form a column of Schwann (endoneureum is essential for proliferation of Schwann cells)
      • Retrograde reaction
        • Chromatolysis in perikaryon
        • Several sprouts of axons emerge from proximal stump
        • Axon sprouts enter the schwan tubes and guided to reach the target organ
      22/04/2009
    • Axon reaction 06/23/09
    • REGENERATION OF CNS ??
      • Regeneration nerve fibers in CNS is not possible, because :
        • An endoneureum is not present
        • Oligodendrocytes do not proliferate
        • Astrocytes deposit scar tissue (plaque)
      23/06/09
    • THANK YOU 06/23/09