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Skin/Musculoskeletal System > Nervous Tissue > Flashcards

Nervous Tissue Flashcards

1
Q

Be able to describe the principle constituents of nervous tissue and how they vary in terms of distribution in the CNS vs. PNS?

A

a

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2
Q

Be able to describe a unipolar, pseudounipolar, bipolar, and multipolar nerve cell.

A

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3
Q

Be able to explain the distinction(s) between gray matter and white matter.

A

a

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4
Q

Be able to describe the cytology of a ‘generalized’ neuron.

A

Plasma membrane: crucial for developing action potentials
pigments: lipofuson (wear and tear pigment), end product of lysosomal degradation; neuromelanin Rough endoplasmic reticulum (Nissl)

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5
Q

Be able to differentiate between encapsulated and unencapsulated receptors.

A

encapsulated: meissner’s corpuscle, pacinian corpuscle
unencapsulated: free/naked, merkel’s disks, hair follicle plexus

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6
Q

Be able to explain the basis for naming different types of synapses.

A 
Axo-dendritic
Axo-somatic
Axo-axonal
Serial (e.g., axo-axo-dendritic)
dendrodendritic
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7
Q

Be able to describe the structure of a chemical synapse.

A 
Pre-synaptic structure
-Neurotransmitter containing vesicles
-Pre-synaptic dense projections
-Neurofilaments
-Mitochondria
Synaptic cleft
Post-synaptic structure
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8
Q

Be able to explain what synaptic vesicle recycling and renewal mean.

A

a

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9
Q

Be able to explain the difference types of axonal transport. Be able to explain what dyneins and kinesins do and what orthograde and retrograde transport mean.

A

Slow component:

  • Rate: 0.5-3 mm/day
  • Only in orthograde direction
  • Materials transported:
  • Non-packaged molecules
  • Cytoskeletal components
  • Mechanism not clear

Fast component
-Rate:
~Orthograde: 400 mm/day
~Retrograde: 1/2 to 2/3 speed of orthograde rate
`Materials transported
~Orthograde:
synaptic vesicles; mitochondria, etc
Membrane associated proteins (acetylcholinesterase)
~Retrograde
Worn out membranes of synaptic vesicles; mitochondria; etc.
Clinical, developmental, and experimental significance

Orthograde motor: kinesin (ATPase)
Retrograde motor: dynein (ATPase)

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10
Q

Be able to describe the basic structure and function of the following glial (neuroglial) cell:
astrocytes

A

Fibrous & protoplasmic versions
Golgi staining vs H&E staining
Cell processes:
-Pervasive; terminate in “end-feet”
-End on blood vessels
~Form layer outside basement membrane of endothelial cells
~May help induce formation of tight junctions between endothelial cells
-External & internal glial limiting membranes

Probable functions

  • Structural support
  • Uptake of excess potassium from extracellular spaces during intense or prolonged neuronal activity
  • Phagocytosis & scar formation (gliosis) after injury
  • Isolation of nerve terminals from each other
  • Regulation of entry of substances into interneuronal space
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11
Q

Be able to describe the basic structure and function of the following glial (neuroglial) cell:
oligodendrocytes

A

Functions
Myelination of CNS axons

black and small on a stain

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12
Q

Be able to describe the basic structure and function of the following glial (neuroglial) cell:
microglial cells

A

< 5% of all glial cells

Monocyte ancestry

Function: phagocytosis

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13
Q

Be able to describe the basic structure and function of the following glial (neuroglial) cell:
ependymal cells

A

Line central canal of spinal cord and ventricles of brain

Simple cuboidal to columnar epithelium that is ciliated

Functions

  • Cilia help move the CSF
  • Transport of substances from CSF into brain
  • Secretion into ventricles

Choroidal epithelium

  • Roof of four ventricles
  • Covers the choroid plexus
  • Control composition of CSF produced by choroid plexus
  • Cells attached to each other via tight junctions
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14
Q

Be able to describe the different connective tissue coats of a peripheral nerve.

A

Epineurium: around fascicles of axons

Perineurium: around bundles of axons

Endoneurium: around individual fibers

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15
Q

Be able to differentiate between an unmyelinated and a myelinated axon.

A 
Unmyelinated Nerves (PNS):
Axons (less than 1 m in diameter)
Sheath of Schwann (neurilemma)
Definitions
-Mesaxon
-Bundle of Remak
-C fibers
Occurrence: 
-Axons of post ganglionic autonomic neurons
-Axons of small sensory neurons in dorsal root -ganglia
Myelinated Nerves (PNS)
Axon; myelin; sheath of Schwann
Myelin composition: 80% lipid; 20% protein
Nodes of Ranvier
Internodes
Schmidt-Lantermann clefts
A & B fibers are myelinated
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16
Q

Be able to explain how

axons become myelinated in the PNS and CNS.

A

Jelly-Roll Theory
Intraperiod line
-lighter line, where material gets squeezed to

Major dense line
dark line, where things get stuck as cytoplasm is squeezed out

Internal & external mesaxons

17
Q

node of

Ranvier

A

unmylenated areas of axons

18
Q

Schwann cell

A

a

19
Q

mesaxon

A

a

20
Q

internode

A

a

21
Q

Schmidt-Lantermann cleft

A

a

22
Q

Be able to describe the structural similarities and differences of a typical sensory ganglion and typical autonomic ganglion.

A

Sensory ganglia

  • Dorsal root ganglia; sensory ganglia of cranial nerves V, VII, VIII, IX, and X
  • Nerve cells are pseudounipolar; cell bodies are in the ganglia
  • A to C fibers
  • Light and dark cells
  • No synapses in ganglia
  • Satellite cells (capsule cells)
  • Fibroblasts
  • C.t. capsule

Autonomic ganglia
-Sympathetic ganglia
~Discrete structures with capsules: superior cervical, celiac, superior mesenteric, etc.

Parasympathetic ganglia
-Small and encapsulated in head; elsewhere simply isolated clusters of cells: ciliary or otic ganglia in head; submucosal and myenteric plexi of gut
-Preganglionics synapse with cell bodies of postganglionic neurons
-Cell bodies of postganglionic neurons
~multipolar neurons
~Eccentric nuclei; sometimes binucleate
~Axons terminate on effector organs (smooth muscle; cardiac muscle; glands)
-Myelination
~Preganglionics are small, myelinated B fibers
~Postganglionics are small, unmyelinated C fibers
-Connective tissue and fibroblasts are present
-Neurotransmitters
~Acetylcholine: at termination of preganglionics of both sympathetic and parasympathetic fibers
~Acetylcholine: at termination of postganglionic parasympathetics
~Norepinephrine: at termination of postganglionic sympathetics except for acetylcholine for sympathetic innervation of sweat glands

23
Q

Be able to explain what satellite cells are

A

Autonomic ganglia
Satellite cells and Schwann cells
-Represent the glia of the PNS
-Satellite cells form incomplete covering of cell bodies
-Schwann cells associated with nerve fibers running through ganglia

24
Q

Be able to describe some of the basic characteristics of degenerative and regenerative processes of
nerves cells.

degeneration

A

Wallerian (Orthograde) Degeneration

  • Axon, axon terminals, myelin disintegrate
  • Schwann cell sheath and c.t. layers remain in PNS; no CNS counterpart
  • Phagocytosis of debris (Schwann cells & macrophages)

Retrograde degeneration
Degeneration of axon and myelin sheath in direction of cell body
Chromatolysis
Death of cell (with or without chromatolysis)
Severity levels: cell type; site of lesion; nature of injury; age of individual

25
Q

Dendrites

A

Provide receptive areas for receipt of input
Axon terminals of nerve cells in CNS and autonomic ganglia of PNS
Sensory receptors in PNS

Frequently determine characteristic shapes of different nerve cell types

26
Q

Axon

A

Sends information via a synapse to:

  • Another nerve cell in the CNS or autonomic ganglia of the PNS
  • An effector organ in the PNS

Features

  • Single but can have collateral branches
  • Myelinated or non-myelinated
  • Great variability in length
  • Constant in diameter from end to end
  • Diameter & length vary with size of cell body
  • Terminal branching to form up to 1000 or more terminals or telodendria
Specific regions
-Axon hillock
-Initial segment
Contents
-No r-er or ribosomes
-Synaptic vesicles in terminals
-Microtubules
Coverings: glial & connective tissue
27
Q

peptidergic neuron vs small molecule releasing neuron

A

peptidergic: packaging of neurotransmitter in cell body, released in axon

small molecule releasing: packaging and release in axon

28
Q

Neuroglia

A 
General features:
Small
Ubiquitous
Out number neurons 10-50:1
Multiple processes per cell
Can be difficult to distinguish with normal H&E stains
29
Q

Coverings of Nerves (CNS)

A

Unmyelinated fibers: no associated glial cell

Myelinated fibers:
Oligodendrocyte responsible

30
Q

Be able to describe some of the basic characteristics of degenerative and regenerative processes of
nerves cells.

regeneration

A 
Regeneration
-Successful only in PNS
-Success depends partly on type of injury
Specificity of reinnervation
Traumatic neuromas
Aborted CNS regeneration attempts

CNS regeneration is usually abortive

  • Oligodendrocytes do not form a guiding tube
  • Scar tissue produced by astroglia is a significant barrier
31
Q

Traumatic neuromas

A

Heterogeneous mass of entangled nerve fibers, Schwann cells, connective tissue cells, etc.

Occurs if regenerating neurons cannot overcome obstacles between the cut ends of the nerve

Afferent neurons in neuromas still send messages centrally and are often interpreted as pain

32
Q

Specificity of reinnervation

A
  • Sensory fibers will innervate any sensory receptor: sensation therefore usually less critical than before injury
  • Motor fibers will innervate any muscle and give the muscle the character of the regrowing nerve: movements are less discrete than before the injury
  • Regenerated axons have smaller diameters and thus conduction velocity is decreased

Skin/Musculoskeletal System (14 decks)

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