Structure of Nerve Tissue - X Flashcards
Internerouns
Interconnect other neurons, 99.9% of all neurons
GVE - information pathway
**
Ventral root of spinal cord, through ventral root out to smooth and cardiac muscle, glands, etc
Two neuron chain
GSA - movement of information, how
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Bring in information from the periphery/body to Spinal Cord.
Cell bodies located in Dorsal Root Ganglion
Information flows through the dorsal root into the dorsal horn of the spinal cord
Multipolar - def, e.g.
**
most common
1 axon, 2+ dendrites
motor neurons and interneurons
Cell Body - characteristics
large pale staining nucleus dispersed chromatin nucleoli Lots of RER and Nissl bodies (free ribosomes) numerous mitochondria
Unipolar/ psuedounipolar - def, e.g.
1 long axon divides close to cell body into 2 long axial branches
typically prokaryotic
eukaryotic evolution - DRG cells
Axon Hillock - def, significance
initial segment of axon w/o Nissl bodies or Golgi
sight of nerve impulse generation - very excitable
Bipolar - def, e.g.
**
1 axon, 1 dendrite
associated with receptors for special senses
Retrograde
towards cell body
Mediated by Dynein
viruses could be taken up nerve terminal and transferred int CNS
Rate : FAST
Anterograde - axonal transport
away from cell body
mediated by Kinesin
two rates : Slow (same as peripheral regeneration)
Fast
Neurofilaments - fxn
support
role in neuronal development and regeneration
Microfilaments - def, fxn
actin
Anchor
transfer molecules to/from cell membrane
Cause movement of growing axonal tips during development and regeneration
Microtubles
**
cylindrical assemblies of tubuli, with axonal transport proteins
Presynatic terminal - a..k.a
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buton
Synapses - catergories
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axo-dendritic (majority))
axosomatic
axoaxonic
dendrodentritic
Neuromuscluar junction
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specialized synapses on skeletal muscle
ACH as nt
junctional folds on muscle fiber membrane
Neuroglial cells - fxn, types
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support and myelination in PNS
Peripheral = Schwann and Satellite cells
Schwann Cells - fxn
**
Myelinate peripheral axons
Myelin sheath - concentric rings of Schwann around axon
also surrounds/nurtures unmyelinated axons
thicker myelin = faster conduction
DRG
contains cell bodies of pseudounipolar sensory neurons
cell bodies surrounded by satellite cells
NO synapses occur here
Schidmt-Laternams clefts - def., fxn
islands of Schwann cytoplasm bwtn lamellae of myelin
= characteristic fishbone appearance on LM
fxn - Intracelluar communication
Autonomic Ganglia - characterstics
Multipolar
Synapses OCCUR
Sateliite Cells - def, fxn
glial cells that surround peripheral ganglia
Maintain controlled local enviroment
Provide electrical insulation
Path for metabolic exchange
CT coverings on nerves
Epineurium
Perineurium
Endoneurium
Epineurium
Surround entire nerve
Node of Raniver
**
btwn two adjacent Schwann cells (no myelin)
intenodes - have myelin sheath
Nodes have high [Na+] resulting in fast impulse propagationsaltatry transmission ‘jumping’
Perineurium
Surround fascicle ( bundle of nerve fibers)
Permeability barrier - a.k.a , fxn
blood-nerve barrier btwn perinuerial fibroblasts surrounding nerve fascile
maintains ionic environment of nerve fibers
Permeability barrier - a.k.a , fxn
blood-nerve barrier btwn perinuerial fibroblasts surrounding nerve fasicle
maintains ionic environment of nerve fibers
Kinesthesia
Detection of movement through space
Guillain-Barré syndrome
autoimmune condition - destroys Schwann cells by T cell response against peripheral myelin.
Loss of cutaneous sensation.
Symmetrical ascending weakness.
Pt can survive and recover
Nerve Injury Classification - +action
XX
mild compression - demyelination
nerve crush - axons disconnected
complete transection - whole nerve
Endoneurium
surround individual axons
Nerve Regenration
**
Rate slow - into distal stump
If damaged, some axons grow endoneurial tubes, reestablishes contact with muscle
If growths disorganized, can lead to painful traumatic neuroma at site of injury
anterograde Wallerian Denegeration
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Distal to injury/cut
- axon swells, disintegrates, removed by macrophages
- Schwann cell dedifferetiate, breaking down myelin sheath and blood-nerve barrier
- Schwann cells secrete growth factors, divide and line up as guidance for new axon sprouts
Retrograde Chromatolysis
**
Proximal in cell bodies of origin
- Cell body swells
- Nucelus Shifts to periphery
- Nissl substance (RER) breaks down
GVA
wall of internal organs, glands and blood vessel to spinal cord
GSE
CNS to voluntary skeletal muscle
cell bodies in ventral horn, exit through ventral roots
