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Cell & Tissue Biology > L17: Nervous Tissue I > Flashcards

L17: Nervous Tissue I Flashcards

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1
Q

What is perikaryon?

A
  • Soma or cell body of neuron
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2
Q

Classification of neuron types

A
  • Multipolar (angular soma) = most common type
  • Bipolar (ovoid soma)
  • Pseudo-unipolar (spherical soma)
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3
Q

What are bipolar neurons associated with?

A
  • Neurons associated with special senses: vision, sound, smell, balance…
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4
Q

Where are pseudo-unipolar neurons located?

A
  • In DRG, trigeminal and other CN ganglia
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5
Q

Are nuclei of neurons euchromatic or heterochromatic?

A
  • Euchromatic, cells never sleep
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6
Q

What are Nissl bodies / substance?

A
  • Stacks of rER in neurons, indicative of large amount of protein synthesis occurring
  • Basophilic
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7
Q

Organelles found in dendrites, axons?

A
  1. ) Dendrites: mitochondria, free ribosomes, rER may be found. No golgi
  2. ) Axons: mitochondria, microtubules, neurofilaments, vesicles, sER. No rER
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8
Q

What is the axolemma and axoplasm?

A
  • Cell membrane specific to axon

- Cytoplasm specific to axon

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9
Q

Initial segment?

A
  • Segment of axon distal to axon hillock and proximal to myelination
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10
Q

Collateral branches

A
  • Axons branches near hillock
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11
Q

How to distinguish Axon hillock under microscopy?

A
  • Pale staining, indicative of no rER
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12
Q

What pigment is found in neurons?

A
  • Lipofuscin (wear and tear pigment) – represents old degraded membranes in lysosomes, which there is no mechanism to get rid of. Gets in way of neural function eventually
  • Neuromelanin, by-product of dopamine synthesis (highly found in substantia nigra of midbrain)
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13
Q

Function of dendrites?

A
  • Receptive surfaces of neuron, large number of them increase receptive surface area of neurons
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14
Q

What is myelin’s function?

A
  • Increase conduction rate and insulate axons
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15
Q

What myelinates?

A
  • Oligodendrocytes in CNS

- Schwann cells in PNS

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16
Q

Discuss two types of axoplasmic transport

A
  1. ) Anterograde (A=away from cell body): via kinesin
    a. ) slow transport (of tubulin, actin, neurofilaments)
    b. ) fast transport: requires ATP
  2. ) Retrograde (R=return to cell body): via dynein**
    a. ) fast transport system (of sER, vesicles, mitochondria, AAs, sugars, NTs, nucleotides, Calcium): requires ATP
    * * Viruses and toxins that enter nerve endings use this system
17
Q

What are neuroglia/glial cells/glia?

A
  • Support cells that provide physical and physiological support to neurons
18
Q

Types of neuroglial cells. Function of each?

A
  1. ) Protoplasmic/fibrous astrocytes: feet (pedicels) cover surfaces of capillaries in brain and spinal cord, specifically capillaries with basal lamina, monitoring chemical composition in extracellular space – therefore acts as blood brain barrier, forms scar tissue. Protoplasmic in gray matter. Fibrous in white matter.
  2. ) Microglia: vacuum cleaners/phagocytic cells of CNS
  3. ) Oligodendrocyte: myelin forming cells of CNS
  4. ) Ependymal cells: line brain and spinal cord cavities containing CSF, cover choroid plexus
  5. ) Schwann cells: myelin forming cells of PNS
  6. ) Satellite cells: support cells that surround cell bodies of neurons in ganglia, function analogous to Schwann cells without formation of meylin
19
Q

What structural filaments are found in neurons?

A
  • Neurofilaments (intermediate)
  • Microfilaments (actin)
  • Microtubules
20
Q

Clinical relevance of astrocytoma

A
  • Astrocytomas are primary brain tumors from fibrous astrocytes that make up about 80% of adult primary brain tumors
21
Q

Clinical relevance of ependymoma

A
  • Accounts for 5% of brain tumors from ependymal cells
22
Q

Why do brain cancers arise from glial cells?

A
  • Neurons don’t divide (as general rule) and therefore don’t form tumors.
  • Glial cells do however, therefore most primary brain tumors arise from glial cells, not neurons.
23
Q

Are unmyelinated axons in the PNS associated with myelin? Associated with Schwann cells?

A
  • Not associated with myelin, but they are associated with Schwann cells, which given them a hug
24
Q

What is myelin? What does it consist of?

A
  • Myelin consists of lipoprotein and is formed by concentric layers of a cells membrane by oligodendrocytes (in CNS) and Schwann cells (in PNS) wrapping around axons. Not secreted.
25
Q

What are internodes?

A
  • Myelinated areas on an axon, which are separated by nodes of Ranvier
26
Q

What is the area in a myelinated area where some cytoplasm gets trapped?

A
  • Shmidt-Lanterman cleft = cytoplasm trapped in concentric layers of cell membrane myelinated an axon
27
Q

What are the CT coverings found on axons? Are these coverings found in PNS and CNS?

A
  • Endoneurium: surrounds single axons, loose CT with collagen fibrils
  • Perineurium: surrounds bundle of axons, specialized CT lined with perineural cells, zonula occludens
  • Epineurium: surrounds multiple bundles of axons, contains vascular supply to neurons, dense irregular CT with elastic fibers
  • only in PNS associated with nerves, not CNS
28
Q

What are the layers surround axons?

A
  • Endoneurium (outer)
  • Basal lamina (middle)
  • Myelin (inner)
29
Q

What is multiple sclerosis?

A
  • Autoimmune disease affecting only the CNS
  • Affects the white matter, which refer to axons myelinated by oligodendrocytes
  • Pathology in oligodendrocytes causes antibodies to form and attack myelin sheath – oligodendropathy
  • Leads to demyelination of axons
  • Any myelinated tract may be affect
  • Leads to sclerotic plaques on axons that affect impulse transmission
  • Most common cause of optic neuritis = MS
30
Q

Functional classification of neurons

A
  1. ) motor (efferent) – multipolar
    a. ) skeletal motor (somatic efferent) – to skeletal muscle fibers
    b. ) visceral motor (visceral efferent) – to smooth muscle, cardiac muscle or glands – autonomic
  2. ) sensory (afferent) – pseudo-unipolar
    a. ) somatic afferent – sensory stimuli from environment
    b. ) visceral afferent – sensory stimuli from viscera

3.) interneurons – multipolar

31
Q

Are nodes of Ranvier only present in PNS?

A
  • No, both in CNS and PNS.
32
Q

Mesaxon

A
  • This is fused cell membranes

Cell & Tissue Biology (18 decks)

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