Repairing Nervous Tissue Flashcards
2 Main Cell Types of Nervous Tissue
Neurons Support cells (Neuroglia)
Function of nervous tissue
Taking & Integrating info from int. & ext. milieu (environment)
Main function of PNS
Receiving info
Main function of CNS
Integrating, analysing & responding
What do the meninges protect?
Brain
Spinal Cord
Blood vessels of both
What is a neuron?
Structural & functional unit of nervous system
Draw a neuron
See diagrams
What are the 3 types of neuron?
Draw them.
Multipolar
Pseudounipolar
Bipolar
What is gray matter made of?
Cell bodies
What do axons of neurons make up?
White matter
Name for collection of cell bodies in PNS & CNS?
PNS = Ganglia CNS = Nuclei
Other name for Cell Body of neuron?
Perikaryon
Where do Action Potentials start in neurones?
Axon Hillock
What does Nissl substance stain?
Which parts of the neurones remain unstained?
Rough Endo Reticulum & Polyribosomes (used for protein synthesis)
Axons remain unstained (Perikaryon & Nucleolus stained)
What makes up Metencephalon?
Cerebellum & Pons
What is the myelencephalon?
Medulla
How many layers of neocortex?
Name them.
6 1 = Molecular 2 = Int Granular 3 = Int Pyramidal 4 = Ext Granular 5 = Ext Pyramidal 6 = Multiform
What are layers made of?
Neurons typical of that layer type
What’s found in layer 4?
Granule/Stellate neuron
Where are small & large pyramidal neurons found?
Small = 3 Large = 5
How many layers in Cerebellar cortex? Name them.
3
1- Molecular
2- Purkinje
3- Granule
What cells are found in Molecular layer of Cerebellar Cortex?
Basket cells
Stellate cells
(Fibres of cells below -e.g Purkinje)
What is the role of Purkinje cells?
Receive aff. info from other parts of CNS
Assimilate info
What do Basket cells do?
Link Purkinje cell bodies
Allow lat. inhibition
What’s found in Granule Cell Layer?
Granule cells
Golgi cells
Most abundant neuron in brain?
Granule cells
Largest cell in cerebellum?
Purkinje
What type of neuron are Purkinje cells? Describe their appearance.
Multipolar
Large pear-shaped body
Extensive dendritic tree
Role of Neuroglia?
Metabolism & structural support of neurones
CNS Neuroglia?
Astrocytes
Ependymal Cells
Oligodendroglia
Microglia
PNS Neuroglia?
Schwann cells
Satellite cells
Different types of Astrocyte
Muller Glia (Retina)
Fibrous (White matter)
Protoplasmic (Gray)
Radial Glia (Specialised - developing CNS)
What is Blood-Brain barrier made of?
Endothelial Cells
Tight Junctions
Astrocyte Foot Processes
Where do Astrocyte foot processes attach?
Blood vessels & along surface of CNS (For forming BBB)
What is role of BBB?
Prevent diffusion of solutes & fluid into brain & spinal cord (prevent infection etc)
What can cross BBB?
O2
CO2
Lipid-soluble molecules (hormones)
<500Da MW molecules
What type of cell are Ependymals?
Ciliated Cuboidal Epithelial
Role of Ependymals?
Secrete & Reabsorb CSF
What is CSF?
Clear, cell-free fluid made in Choroid Plexus
Role of Microglia
CNS immune function
Like Macrophage
Phagocytose debris after injury
How do Microglia respond to injury
‘Resident’
‘Activated’ with injury - migrate to site
Release cytokines (help or hinder recovery)
Role of Oligodendrocytes?
Myelin sheath around CNS axons - One to many
Diseases affecting Oligo’s?
MS
Leukodystrophies
Role of Schwann’s?
PNS myelination
One to one
Organising connecive tissue sheaths around peripheral nerves in development & regen
Composition of Myelin?
80% lipid
Role of myelin?
Insulation
Provide fast conduction velocity for AP’s (Saltatory Conduction)
Which Ganglia can envelope non-myelinated axons?
Schwann cells - can envelope 1 or more
CNS unmyelinated not ass. with glia
How is unmyelinated AP conduction compared to myelinated?
Continuous conduction due to passive current flow
Example of unmyelinated axons?
C fibres - detect itch, temp & pain
How are Dorsal Root Ganglia covered?
Individual ganglia covered by flattened satellite cells
Dorsal Root Ganglia (+ cranial nerves) covered by connective tissue capsules continuous with dorsal root epi- & perineurium
What are Ganglia?
Collections of nerve cells outside the CNS
Describe structure of peripheral nerves
Nerve fibres surrounded by Endoneurium make a fascicle
(Each fibre may be myelinated)
Fascicle surrounded by perineurium
Bundle of fascicles covered by epineurium
What cell bodies are in lateral horn?
Visceral Motor neurons
Where are Somatic motor neuron cell bodies?
Ventral horn
What’s found in Dorsal horn?
Interneurons
What’s in the white matter of spinal cord?
Asc. & Desc. tracts
Where are the Motor tracts?
Ventral columns
Where are sensory tracts?
Dorsal columns
What type of tracts are in lateral columns?
Mixed sensory & motor
Describe Motor Neuron Cell Bodies
Multipolar neurons Large Dorsal Horn Many Nissl bodies Pale-staining nuclei Prominent nucleolus
What nerves can & can’t be repared?
Peripheral nerves can
CNS axons can’t
What’s the name given to the regeneration process of the PNS & CNS?
Wallerian Degeneration
What’s involved in Wallerian Degeneration?
Removal of debris
Foundations laid down for regen/regrowth
Why doesn’t Wallerian work in CNS?
Not efficient
Different cells, neurons & environment to PNS
Explain Wallerian in PNS
- Injury - Distal Axon & myelin damaged
- Schwann cells activate - proliferate & travel to injury site. Plus macrophages start phagocytosing debris
- Schwann cells express growth factors & create Bands of Bungner - nerve fibres grow through these
- Nerve fibres reconnect to end organs & Schwann cells re-myleinate
Explain Wallerian in CNS
- Damage to distal axon & myelin - Astrocytes & Microglia activate. Microglia start phagocytosing. Inflammation.
- Debris not cleared properly. Glial scar formed by astrocytes.
- Regen fails as growth of axons impaired by glial scars & leftover myelin debris
Why do Glial scars form?
‘Reactive’ Astrocytes
Hypertrophic
Inhibitory molecules increase - Chondroitin Sulfate Proteoglycans (CSPG)
Normal molecules increase - GFAP (Glial Fibrillary Acidic Protein)
Axons can’t grow through wall of Scar & Debris
How can you tell repair has failed in CNS?
Axons grow but turn away from lesion
May show reactive ‘end bulbs’ (black splodges) - accumulation of organelles in end bulb
What do Oligodendrocytes contribute in CNS repair?
Myelin debris
Failure
Why don’t PNS glia help out?
Clear boundary/wall between the 2 systems - shown by staining at Dorsal Root Entry Zone
(‘Glial Limiting Membrane’)
