Download CNS

Components of Central Nervous System (CNS)
 Neurons,
Glia: gray matter, white matter
 Neuropil (nerve fibers + glia processes)
 Synapse
 Glia (Neuroglia)
 Astrocyte (Astroglia)
 Microglia
 Oligodendrocyte (Oligodendroglia)
 Ependyma (choroid plexus epithelium)
Histo: CNS - 1
Components: Neurons, Glia and Neuropil
 Gray matter: Neurons (+ processes), Glia
 White matter: Nerve fibers (processes), Glia
 Neuropil: nerve processes + glia processes
Neuropil
Histo: CNS - 2
Synapses


Functional classifications
 Chemical synapse
Neurotransmitters,
Neuropeptides
 Electronic synapse: gap
junction (nexus), connexin
Morphological classification (EM)
Histo: CNS - 3
Chemical Synapses

Ultrastructures
 Presynaptic element: synaptic
vesicles
 Synaptic cleft
 Postsynaptic element: clustering of
receptors/channels

Neurotransmitters
 acetylcholine (ACh), noradrenaline
(NE), gamma-aminobutyric acid
(GABA), serotonin (5-HT),
dopamine (DA), glycine, glutamate,
aspartate etc.
 Neuropeptides (peptidergic):
calcitonin gene-related peptide
(CGRP), etc.
Histo: CNS - 4
Structural classification of
Synapses
 axosomatic
synapse
 axodendritic synapse
 axoaxonic synapse
Axosomatic
Axodendritic
Axoaxonic
Histo: CNS - 5
Neuroglia
Microglia (macrophage)
Histo: CNS - 6
Neuroglia
Non-nervous
elements;
more abundant than
neurons
protective, supportive,
nutritive
Exist in the extraneuronal
space
as ionic sink
little true tissue space, no
lymphatics
Proliferate in CNS injury
Histo: CNS - 7
Types of neuroglia
Astrocytes
(Astroglia)
Protoplasmic, Fibrous
Oligodendrocytes
(Oligodendroglia)
Microglia (Mesoglia)
Ependyma cells, Choroid
epithelium
Histo: CNS - 8
Astrocytes
 Perivascular
feet (Foot
plates)
 “glia limitans” (LM) on
brain surface
 subpia foot of
astrocytes
 basal lamina of pia
matter (EM)
 cytoplasm: glial fibrillary
acidic protein (GFAP)
 ?Functions: barriers,
metabolism
Histo: CNS - 9
Protoplasmic astrocytes
 in
gray matter
 Stellate form with
multiple radiating
processes
 A larger and paler
nucleus than other glial
cells
 Processes ending as
vascular feet/pedicles
(perivascular feet) and
perineural feet
Histo: CNS - 10
Protoplasmic astrocyte
Blood vessel
Cajal method Silver
impregnation
GFAP
Histo: CNS - 11
Fibrous astrocytes
in
white matter, and
periventricular gray
matter
an ovoid euchromatic
nucleus with
pale-staining
cytoplasm and long,
thin processes
Histo: CNS - 12
Fibrous astrocyte
Immunocytochemistry GFAP
Silver-gold impregnation
Histo: CNS - 13
Microglia
 Mononuclear
phagocytic cells
 A dense oval or
elongate nucleus
with scant
cytoplasm
 Tortuous processes
with spines
 Upon injury:
proliferate, loose
spines, become
swollen (“amoeboid”)
Histo: CNS - 14
Microglia
Microgliosis
Silver impregnation
Immunohistochemistry: MHCII (major
histocompatibility complex II) for
activated microglia
Histo: CNS - 15
Oligodendrocytes
 Form
myelin sheath in CNS
 Smaller size than astrocytes
 Small irregularly shaped
deeply stained nucleus
 Various classifications and
Types
 Perineural
oligodendrocytes
 Perifascicular
oligodendrocytes
Histo: CNS - 16
Perineuronal
oligodendrocytes
 Mainly
in gray matter
 Closely associated with
soma of neurons
 ? Functions: metabolic
interdependency
oligo
Histo: CNS - 17
Perifascicular
oligodendrocytes
 Mainly
in white
matter
 arranged in rows
between bundles of
axons
 Analogous to
Schwann cells in
PNS
 forming myelin
sheaths of several
parallel axons, up to
50 or more
Histo: CNS - 18
Oligodendrocytes
Perineuronal
oligodendrocytes
Perifascicular
oligodendrocytes
19
Histo: CNS - 19
Different patterns of myelination between CNS and PNS: 1/3
1. Surface of the node: contacted by astrocyte processes in
CNS; covered by Schwann cell processes in PNS.
2. Cytoplasm of myelinating cells near the node of Ranvier: (-)
for Oligo; (+) for Schwann cells.
Histo: CNS - 20
Different patterns of myelination between CNS and PNS: 2/3
3. One Oligo for several axons; One Schwann for a single axon
4. Distance between cell body and myelin sheath: Oligo >
Schwann
Histo: CNS - 21
Different patterns of myelination between CNS and PNS: 3/3
5. Basal lamina associated with myelin sheath: (-) in CNS,
(+) in PNS
6. Supporting connective tissue for myelinated axons: (-) in
CNS, (+) in PNS
Histo: CNS - 22
Demyelinating diseases
 Myelin
proteins
 only in PNS: peripheral myelin protein 22 (PMP22) etc
 only in CNS: proteolipid protein (PLP) etc.
 in PNS and CNS: myelin-associated glycoprotein (MAG)
etc.
 Demyelinating diseases
 PNS: Guillain-Barré syndrome (acute inflammatory
demyelinating polyradiculopathy) 急性神經根炎
 CNS: multiple sclerosis 多發性硬化症
Histo: CNS - 23
Guillain-Barré syndrome (GBS)
Progressive Day 1
weakness Lower limbs
Day 3
Upper limbs
Day 7
Respiratory failure
Histo: CNS - 24
Ependymal cells
Lining
cells of ventricular system
Ventricles
Aqueduct
Central canal
Choroid plexus: continuous with
ependyma cells of ventricles
Histo: CNS - 25
Ependymal cells
Histo: CNS - 26
Ependymal cells





C: cilia
M:microvilli
JC: junctional complex
BB: basal body
G: Golgi apparatus
Histo: CNS - 27
Choroid plexus
 Ependyma
layer + vascular core
(fenestrated vessels + loose
connective tissues)
 Produce cerebrospinal fluid (CSF)
Histo: CNS - 28
Blood-Brain Barrier (BBB)
 Nonfenestrated
(continuous type)
endothelial cells (tight
junctions)
 thick basal lamina with
outer surfaces enclosed by
 Astrocyte foot processes
(perivascular feet, end feet)
Histo: CNS - 29
Blood-Brain Barrier
 Capillary
of continuous type; Thick
basal lamina; Perivascular feet
 Functions: impermeable to foreign
substances for preventing
 Autoimmune damage
Blood vessel
Histo: CNS - 30
Meninges
 Dural
mater
(pachymeninx)
 periosteum of
skull
 subdural space
 Pia-arachnoid
(leptomenginges)
 Arachnoid mater
subarachnoid
space / cistern
Intact vessels
 Pia mater
Histo: CNS - 31
Meninges
Histo: CNS - 32
Pia-Arachnoid
Histo: CNS - 33
Organization of CNS
 Cerebellum:
3 layers
 Cerebral cortex (Neocortex): 6
layers (cytoarchitecture:
Broadmann area)
Histo: CNS - 34
Mol: molecular layer
Pkj: Purkinje cell layer
Gr: granular layer
Cerebellum
Cerebellar cortex
Histo: CNS - 35
Pyramidal cells (neurons)
Histo: CNS - 36
Cerebral cortex
(Neocortex): 6 layers
1. Plexiform (molecular) layer
2. Outer granular layer
3. Pyramidal cell layer
4. Inner granular layer
5. Ganglionic layer
6. Multiform cell layer
White matter
Histo: CNS - 37
Response of a nerve to injury
Histo: CNS - 38
Nerve Degeneration and Regeneration
Histo: CNS - 39
Nerve injury: PNS vs. CNS
Histo: CNS - 40
Nerve Degeneration and Regeneration
 Wallerian
degeneration: disintegration of axonal
cytoskeleton distal to the site of injury
 Cell body: chromatolysis (loss of Nissl substance)
 Responses
 PNS: proliferation of Schwann cells; migration of
macrophage
 CNS: proliferation of astrocytes
 Regeneration
 PNS: as a rule
 CNS: negligible
inhibitory molecules, glial scar etc.
Histo: CNS - 41
Review of CNS Histology
 Components
of CNS: neurons, glia
 Neurons, Glia: gray matter, white matter
Neuropil (nerve fibers + glia processes)
 Synapse
 Glia (Neuroglia)
 Meninges (Menix)
 Blood-Brain Barrier
 Organization of the CNS: layers
 Responses to nerve injury
Histo: CNS - 42