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Nerve Flashcards

(39 cards)

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1
Q

Neurons - describe the cell structure

A
  • nerve cell body (soma):
  • large euchromatic nucleus
  • prominent nucleolus
  • Nissl substance (RER, ribosomes –> contains RNA)
  • axon hillock
  • cytoplasmic processes:
  • axons (one per neuron)
    • ensheathed by Schwann cells
    • may be myelinated
  • dendrites (many per motor neuron; none for sensory neuron)
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2
Q

ID the tissue

A

Motor neurons in toluidine blue stain

note the large nucleus and nucleolus

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3
Q

These types of nerve pathways use a single neuron

A

Sensory and motor nerves

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4
Q

Ganglia

A

clusters of nerve cell bodies outside of the CNS

Two types:

  • sensory
  • autonomic (motor)

a) sympathetic
b) parasympathetic
b1) enteric

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5
Q

These types of nerve pathways use two neurons

A

Autonomic motor nerves

  • first neuron cell body resides in CNS
  • second neuron cell body resides in peripheral

ganglia

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6
Q

epineurium, perineurium, endoneurium

A

Types of peripheral nerve connective tissue investments

Perineurium surrounds fascicles while endoneurium are around individual nerve fibers

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7
Q

Describe the photo

A

Peripheral nerve axons tend to separate from the epi/perineurium in cross section

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8
Q

ID the tissue

A

Peripheral nerves tend to be “wavy” in longitudinal section; allows nerve to stretch with skin

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9
Q

ID the tissue

A

Peripheral nerve, wavy

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10
Q

ID the tissue

A

Nerve bundle in trichrome stain, surrounded by collagen

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11
Q

These cells form the blood-nerve barrier

A

Perineurial cells

  • have tight junctions & gap junctions
  • restrict cell entry (no lymphocytes, plasma cells)
  • control transport
  • are contractile
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12
Q

Describe

A

Peripheral nerve cross section

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13
Q

Schwann Cells

A

All peripheral axons are supported by Schwann cells

one Schwann cell will invest multiple unmyelinated axons; however, many Schwann cells will be needed to invest the full length of an axon

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14
Q

Describe

A

All peripheral axons are supported by Schwann cells

S=Schwann cell nucleus

F=fibroblast

There are NO nerve cell nuclei here; most nuclei in peripheral nerv are schwann cell nuclei

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15
Q

Myelin sheath

A

Wraps up in the Schwann cell; insulate and permits fast condution

Very lipid rich so looks empty in stain

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16
Q

Describe

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A

Cross section of an axon

Type III Collagen in top right corner

Neurofilaments are IFs

Microtubules for cargo transport

Neurilemma is cytoplam of Schwann

17
Q

Describe

Study These Flashcards
A

Myelin (lipid-rich) is generally not well-preserved in most preparations

18
Q

neurokeratin

Study These Flashcards
A

residual protein elements in myelin sheath following lipid extraction

19
Q

neurilemma

Study These Flashcards
A

Schwann cell cytoplasm

20
Q

Nodes of Ranvier

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A

one of the myelin interruptions

region where cell depolarizes

allows for saltatory conduction

Sensory neurons and somatic motor neurons are myelinated; autonomic neurons are not

21
Q

Describe

22
Q

Schmidt-Lanterman incisures (clefts)

Study These Flashcards
A

Channels within myelin that runs continuously from axon to Schwann cell

Connects cytoplam of Schwann cell from outer to inner when it’s wrapped up

23
Q

Describe

Study These Flashcards
A

Schmidt-Lanterman incisures (clefts) – gaps in myelin; these are the white spaces between the purple myelins sheaths surrounding the *

Here they used a lipophilic dye which stains the myelination purple

24
Q

Sensory neurons

Study These Flashcards
A
  • examples:
  • dorsal root ganglion
  • cranial sensory nerve ganglia
  • pseudounipolar neurons
  • morphology:
  • central nucleus
  • ring of satellite cells complete because there are no dendrites to disrupt them
  • synapses do not occur
25
Autonomic Neurons
- examples: * sympathetic * parasympathetic (CNs) - **multipolar** neurons - morphology: * **eccentric nucleus** * **dispersed satellite cells**; there are synapses with lots of axons coming in and lots of dendrites present - synapses are abundant
26
Enteric ganglia
enteric plexuses
27
Describe
myenteric (Auerbach's) plexus They have eccentic nuclei which means they must be multipolar -- they are enteric (autonomic) neurons Most of the tissue in the frame is smooth muscle of the gut wall
28
Nerve regeneration
29
Pseudounipolar
Sensory nerves are pseudounipolar
30
Multipolar
Somatic motor & Visceral motor (autonomic) are multipolar
31
Describe
Dorsal root (aka spinal) ganglion This is a photo of cell bodies, because you can see the nuclei -- it's not in the CNS, so must be dorsal root ganglion Because the nuclei are in the center, we know they are sesory cells, which are also pseudounipolar The arrowed nuclei are schwann cells
32
Describe
In the ganglion between the brackets, the nuclei are eccentric so they must be multipolar neurons (likely autonomic neurons) they're surrounded by dense irregular with adipocytes The smaller bundle to the left is a bundle of axons, not another ganglion because there are no cell bodies
33
Describe
Spinal Ganglion (DRG) Where you can see a nuclues, it is in the middle, and there are complete circles of satellite cells surounding the cell body These are SENSORY NEURONS
34
Describe
Autonomic Ganglion The nuclei are eccentric and therefore these must be multipolar The satellite cells are dispersed, not surrounding in complete circles These are AUTONOMIC NEURONS
35
Myelinated axonal regions have what type of ratio with Schwann cells?
1:1 if the axon is mylinated If it's not mylinated, one Schwann cell may wrap around multiple axons
36
Review
Reticular fibers mostly Col III Endoneurium has external lamina
37
Silver stains of nerve fibers
Make axons look dark, mylination is light
38
Describe
Most peripheral nerves will be a mix of myelinated and unmyelinated axons The dark pink rings around the axons are the neurolemma or Schwann cell cytoplasm that stains very well and surrounds the myelin sheath surrounding the axon The dark dots are Schwann cell nuclei
39
Describe
This is an image of an axon Surrounding the axon are the layers of Schwann cell cytoplasm and myelin sheath The **mesaxon** (break in the Schwann cell) is at the 5 o'clock position The Schwann cell has an external lamina that runs all the way around, looks like a fuzzy outline There are reticular fibers (Col III) in the top right and bottom right corners The circles inside the axon are microtubules The dots inside the axon are neurofilaments And the large body in the axon is the mitochondria

Histology (11 decks)

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