Nervous Tissue

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Nervous Tissue
2013-10-23 21:33:02
Anatomy Nervous Tissue

Nerves, neurons, circuits, CNS, PNS, Glial cells, Neuron anatomy
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  1. Subdivisions of Nervous System
    • Central Nervous System (CNS)
    • -Brain
    • -Spinal Cord
    • Peripheral Nervous System(PNS)
    • -All Neural tissue outside CNS
    • *Nerves (Cranial and Spinal)
    • *Ganglia 
    • *Sensory receptors
    • -Carries info between CNS and rest of the body
  2. Functions of Nervous System (SIM)
    • Sensory- Detects internal & external stimuli & transmits to CNS
    • Integrative- Processes, analyzes & stores sensory information; Makes decisions regarding appropriate responses. 
    • Motor- Controls muscles & glands in response to sensory info
  3. Peripheral Nervous System (Functional subdivisions)
    • Sensory Nervous System
    • Motor Nervous System
  4. Sensory Nervous System
    • Transmits all sensory info from receptors to CNS (afferent)
    • Contains Somatic Sensory and Visceral Sensory
    • Contains both CNS and PNS components
  5. Somatic Sensory
    • Receives sensory info from skin, fascia, joints, skeletal muscles and special senses (taste, balance, vision, hearing)
    • Part of the Sensory Nervous System
  6. Visceral Sensory
    • Receives sensory information from viscera and  blood vessels and transports to CNS
    • Part of the Sensory Nervous System
  7. Motor Nervous System
    • Transmits motor commands from CNS to muscles and glands (efferent)
    • Somatic Motor (Voluntary: Skeletal muscle)
    • Autonomic Motor (Involuntary: Cardiac Muscle, smooth muscle, glands)
  8. Neurons
    • Basic unit of Nervous System
    • Most specialized cell in the body
    • Conducts impulses
    • High metabolic rate
    • Long-lived
    • Non-mitotic
  9. Neuroglia (Nerve Glue)
    • Support, nourish and protect
    • Most numerous
    • Mitotic
  10. Soma
    • Cell body of neuron
    • Contains nucleus surrounded by cytoplasm
    • Receives, integrates and sends impulses
  11. Microtubules
    Assist moving materials between cell body and axon of a neuron
  12. Liporfuscin
    Yellow-brown pigment of neuronal lysosomes, accumulates in cytoplasm of neurons
  13. Neurofibrils
    Shape and support of neurons
  14. Dendrites
    • A process connected to cell body of neuron
    • Receive impulse from other Neurons or receptors 
    • Conduct impulse towards cell body
    • Numerous and short branched
  15. Axon
    • Carries impulse away from neuron cell body (efferent)
    • Carries towards: Neuron, Muscle fibers, glands
    • Long and singular
    • Joined to cell body at axon hillock
  16. Telodendria
    • AKA axon terminals 
    • Numerous, fine processes at ends of axon and its collaterals 
    • Swelled tips are called synaptic knobs; strings are varicosities
  17. Unipolar neuron
    • One process (Dendrites and axon fused)
    • Cell bodies usually located in ganglia 
    • Usually Sensory (Pain, touch, pressure, temperature)
  18. Bipolar Neurons
    • Two processes extend directly from cell body: One dendrite and one axon
    • Rare; Special sensory (eye, inner ear, olfactory epithelium)
  19. Multipolar Neuron
    • Contain several dendrites and one axon
    • Most common
    • Motor neurons and interneurons
  20. Afferent vs Efferent
    • Afferent - Signal sent from nerve receptors to spinal cord and brain
    • Efferent - Signals sent from brain to peripheral body.
  21. Functional classification of Sensory Neurons
    • -Afferent
    • -Transmit from receptors to CNS
  22. Functional classification of Motor Neurons
    • -Efferent
    • -Transmit from CNS to Effectors (Muscles or glands)
  23. Functional classification of Interneurons
    • CNS
    • Integrate Sensory AND Motor
    • Most numerous
    • Decide how body responds to stimuli
  24. Two types of Astrocytes
    • Fibrous Astrocytes (Mainly in white matter)
    • Protoplasmic (Gray matter)
  25. Astrocytes
    • Most numerous
    • Processes make contact with blood capillaries, neurons, and pia matter.
    • Assist with blood brain barrier
    • Fill spaces, provides support
    • Assist in neuronal development
    • Help maintain appropriate chemical environment
  26. Ependymal Cells
    • Type of Glial Cell
    • Ciliated cubodial/columnar cells epithelial cells 
    • Line ventricles & Central canal
    • Form Choroid plexus with blood capillaries
    • Produce & help circulate CSF
    • CNS
  27. Choroid Plexus
    • Made from Ependymal cells and blood capillaries
    • Produces cerebrospinal fluid; A clear liquid that bathes the CNS and fills internal cavities
  28. Microglia Cells
    • Type of Glial Cell
    • They're small, wondering phagocytes
    • Derived from monocytes 
    • Lowest glial cell in number in CNS
  29. Oligodendrocytes
    • Large bulbous type of Glial cell
    • Provide myelin sheath to axons in CNS
    • Myelinates axons of multiple neurons
  30. Two types of glial cells in PNS
    • Satellite cells 
    • Neurolemmocytes
  31. 3 types of Glial cells in CNS
    • Ependymal Cells
    • Microglial Cells 
    • Oligodendrocytes
  32. Satellite Cells
    • PNS Glial Cells
    • Flattened cells around cell bodies of ganglia
    • Provide structural Support
    • Regulate exchange between neuronal cell bodies a& interstitial fluid
  33. Neurolemmocytes (Schwann Cells)
    • PNS Glial Cell
    • Can enclose many axons
    • Provides myelin sheath to axons in PNS Myelinates only single axon
    • Participates in axon regeneration
  34. Myelination of Axons
    • Sheath composed of multi-layers of glial plasma membrane
    • Neurofibril nodes - gaps in myelin sheath 
    • Provided by: Neurolemmocytes (PNS) from inner myelin sheath & outer neurilemma; Oligodendrocytes (CNS) form myelin sheath
    • Insulates
    • Increase speed of conduction
  35. Two types of nerve conduction
    • Continuous- Typical of non-myelinated axons (Slower)
    • Saltatory- occurs along myelinated neurons; no current where myelinated; Action potential jumps from neurofibril node to node; much faster
  36. Requirements of axon regeneration
    • Must be in the PNS
    • Requires: Intact cell body, functional neurolemmocytes & intact neurilemma, slower formation of scar tissue.
  37. Process of axon regeneration
    • Chromatolysis- Nissi bodies break up in to fine granular masses.
    • Wallerian degeneration of distal end of axon and myelin sheath
    • Phagocytosis of debris
    • Mitosis of neurolemmocytes, grow toward each other forming "regeneration tube"
    • Axon regrows within tube (proximal to distal)
    • New Myelin sheath forms around regrown axon
  38. Synapse 
    • Intercellular junction between neuron and:
    • Another neuron
    • Muscle cell
    • Gland cell
  39. Presynaptic neuron
    • Converts electrical signal into chemical signal
    • Sends the signal
  40. Post-synaptic neuron
    Receives the mesage
  41. Axodendritic
    From axon to axon dendrites
  42. Axosomatic
    From axon to axon cell body
  43. Axoaxonic
    From axon telodendria to axon telodendria 
  44. Synaptic cleft
    Seperates presynaptic and post synaptic cells
  45. Neurotransmitters
    Are the chemical signal
  46. Electrical Synapse 
    • Ions flow through gap junctions
    • A large number or cells can produce action potentials in unison 
    • Faster communication
    • Can synchronize a group of neurons (or muscle fibers)
    • -ie. digestive movements or heartbeat
  47. Chemical synapse
    • Has a synaptic cleft that separates pre and post synaptic cells
    • Pre synaptic neuron much convert electrical to chemical signal
    • Send neurotransmitters 
    • Slower relay in information 
  48. Neural Circuit 
    Functional group of neurons that process specific types of information
  49. Simple series circuit 
    Presynaptic neuron stimulates a single spot-synaptics neurons (the 2nd stimulates another ect)
  50. Diverging Circuit
    • Single pre-synaptic neuron stimulates several post-synaptic neurons
    • This arrangement amplifies the signal
    • Ie. A sensory impulse can be relayed to several brain regions
  51. Reverberating circuits 
    • Collaterals from later neurons synapse with earlier ones
    • Sends signals back through the circuit again and again
    • ie. Breathing suring sleep
  52. Parallel After-discharge circuit 
    • A sing presynaptic cells stimulates groups of neurons & each group synapses with a common post-synaptic neuron 
    • Impulses reach final output cell at different times 
    • Ie. Precise mental activities - Mathematical calculations 
  53. Nerves
    • Bundles of parallel axon in PNS
    • Functionally classified as sensory, motor, and mixed
    • Organized by three CT coverings: Endonerium (each axon) Perineurium  (Each fascile), epineurium (all fasicles covering nerve)
  54. Endonerium 
    • Areolar connective tissue 
    • Separates and electrically isolates each axon
  55. Perineurium 
    • Dense Irregular connective tissue 
    • Supports blood vessels supplying the capillaries within the endoneurium 
  56. Epineurium
    • Dense irregular connective tissue ancloses the entire nerve
    • Provides support and protection to fascicles within
  57. Parasympathetic and Sympathetic are subdivisions of 
    The Autonomic nervous system