Nervous Tissue

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Author:
mnm2186
ID:
29824
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Nervous Tissue
Updated:
2010-08-20 12:29:18
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Histology
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Exam 2
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  1. What is the origin of the CNS?
    Neural tube (via notochord)

    except microglia!!!
  2. What is the origin of the PNS?
    Neural Crest
  3. What is the origin of the ANS?
    Neural Crest
  4. (CNS) Grey matter
    • - Neuronal cell bodies / processes
    • - Astrocytes
    • - Microglia
    • - Some oligodendroglia

    (Neurons organized by function into nuclei)
  5. (CNS) White Matter
    • Myelinated axons
    • (myelin formed by oligodendroglia)
  6. Wiger stains
    • white matter (black)
    • gray matter (gray)
  7. FAS Blue stains
    stains myelin
  8. Cresyl violet stains
    a.k.a. Nissl stains

    Stains nissl substance (RER / polysomes)
  9. Histological appearance of neuron in spinal cord gray matter
    • Motorneuron
    • • euchromatic nucleus (highly active)
    • • prominent nucleolus
    • • abundant Nissl substance (RER / polysomes)
  10. cytoplasm = basophilic
  11. All CNS cell types are derived from neural tube except ________?
    • Microglia
    • (bone marrow origin)
  12. CNS Cell Types
    • - Neurons
    • - Glia (support cells)
    • 1. Ependymal cells
    • 2. Choroid plexus cells
    • 3. Astrocytes
    • 4. Oligodendrocytes
    • 5. Microglia
  13. Ependymal cells
    • Lines ventricles of brain / central canal
    • - Cuboidal cells linked by desmosomes
    • - Apical microvilli & cilia
    • - Abundant mitochondria

    looks like epithelium (neural tube = ectoderm derived)
  14. Tanycytes
    • Specialized ependymal cells (third ventricle)
    • - Linked to each other and to ependymal cells by tight junctions
    • - Basal processes form end-feet on blood vessels
  15. Choroid plexus cells
    • Secrete CSF
    • - Cuboidal epith. linked by tight junctions
    • - Apical microvilli
    • - Infolding of basal plasma membrane
    • - Abundant mitochondria
  16. Fibrous Astrocytes
    • White Matter
    • - long slender processes packed w/ intermediate filaments
    • - filaments composed of glial fibrillary acidic protein (GFAP)
    • - use antibodies to GFAP to determine if neural tumor is of astrocytic origin
    • - structural support for white matter tracts
  17. Protoplasmic Astrocytes
    • Gray Matter
    • - short, thick. bushy processes
    • - fewer intermediate filaments
    • - stains less intensely w/ GFAP antibodies
    • - supportive cells for neurons (growth factors)
  18. Astrocyte cytoplasmic processes (end-feet)
    • End-feet
    • - Cover neurons (soma / dendrites)
    • - Create barrier along the pia mater (glia limitans)
    • - Create barrier around CNS blood vessels (blood-brain barrier)
  19. Oligodendroglia
    Myelination of CNS axons (up to 50 each)

    Some act as satellite cells (not myelinating cells)
  20. Microglia
    • Phagocytic cells (Bone marrow origin)
    • - Resting macrophages in CNS derived from monocytes
    • - Migrate to CNS during development of CNS vasculature
    • - Respond to CNS injury
  21. Microglial response to CNS injury
    • Divide and phagocytize injured neurons and glia
    • - microglial nuclei enlarge / elongate (rod cells)
    • - increased damage = cells become phagocytic (gitter cells)
  22. Histological features of Cerebellum
    Outer layer -> inner layer

    • - Molecular layer
    • - Purkinje cell layer
    • - Granule cell layer
  23. Histological features of Cerebral Cortex
    Small neuroglia

    Pyramidal cells (apical dendrites)
  24. What are the 3 regions of neurons?
    • Receptor region
    • Soma / Nissl bodies / Axon hilock

    • Conductive region
    • Axon / Node of Ranvier

    • Effector region
    • Telodendron
  25. Where are all the protein synthetic organelles found in a neuron?
    Neuronal cell body
  26. Proximal vs. Distal synapses
    (Receptive region)
    Synapses closer to the cell body have more influence than those more distal
  27. True or False:
    Dendrites display an action potential
    FALSE

    • Inputs (excitatory / inhibitory) summate to cause a graded potential
    • (i.e. membrane potential becomes more +/ - depending on input)
  28. Axons vs. Dendrites
    • Dendrites
    • proximal parts have nissl substance
    • diameter tapers distally
    • irregular contours
    • branches bifurcate @ acute angles
    • use graded membrane potential

    • Axons
    • No nissl substance
    • uniform diameter
    • smooth contours
    • branches @ obtuse angles
    • use action potential
  29. Molecular structure of axons
    • Neurofilaments (maintain axon diameter)
    • Microtubules (fast anterograde / retrograde transport)
    • Neurofilaments are more abundant
  30. Slow Axonal Transport
    • 0.2 - 4 mm/day
    • Anterograde only
    • Conveys structural elements
    • (tubulin / neurofilament proteins / actin)
  31. Removal of materials carried by slow transport
    1. Neurofilaments / microtubules are transported as polymers

    2. Disassembled @ axon terminal (due to high Ca+ environment)

    w/o this process, axons will swell (protein accumulation)
  32. Fast Axonal Transport
    • 20 - 400 mm/day
    • Microtubule dependant (motor protein)

    • Anterograde - Kinesin (ATPase)
    • conveys organelles
    • (mitochondria / synaptic vesicles / SER)
    • Retrograde - Dynein
    • conveys worn organelle / endocytosed materials
    • (growth factors / toxins / viruses)
  33. How do neurons grow toward their targets?
    Uses fast retrograde axonal transport

    • Neuron targets make growth factors
    • (carried back to soma by dynein)
  34. Lipofuscin
    Material in retrogradely transported endosomes

    Cannot be digested (lysosomes in soma)

    Accumulates w/ age & in some diseases
  35. Types of synapses
    • 1. Chemical
    • - most common
    • - excitatory / inhibitory

    • 2. Electrical (present in some parts of CNS)
    • - allows neurons to act in unison
    • - gap junctions
  36. Communication @ synapses
    • 1. Presynaptic membrane depolarizes
    • 2. Induces opening of Ca+ channels (brief)
    • 3. Ca+ influx promotes exocytosis of synaptic vesicles
    • 4. Release of neurotransmitters (synaptic cleft)
    • 5. Neurotransmitters react with receptors
    • 6. Postsynaptic membrane depolarizes
    • 7. Presynaptic membrane retrieval (coated vesicles)
  37. Dorsal Root Ganglion
    • Contains sensory neurons that signal:
    • - pain
    • - temperature
    • - touch
    • - pressure
    • - vibration
    • - porprioception
  38. Site of blood-nerve barrier in peripheral nerves
    Perineurium
  39. Axatomy Response
    • Due to loss of target-derived neurotrophic factors
    • 1. cell body swells
    • 2. dissolution of Nissl substance (chromatolysis)
    • 3. nucleus moves eccentrically
    • 4. actin / tubulin genes up-regulated (growth cone)
    • 5. neurofilaments / neurotansmitters down-regulated
  40. Axonal degeneration (injury)
    • Proximal part = retrograde degeneration
    • Distal part = anterograde (wallerian) degeneration

    Distal part separated from cell synthetic machinery
  41. Axonal growth cone
    • Motile structure w/ receptors for neurotrophic factors / laminin
    • (basal lamina surrounds schwann cells)

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