1 Histo: 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)

2 Histo: CNS -

Components: Neurons, Glia and Neuropil

Neuropil

Gray matter: Neurons (+ processes), Glia White matter: Nerve fibers (processes), Glia Neuropil: nerve processes + glia processes

3 Histo: CNS -

Synapses Functional classifications

Chemical synapse Neurotransmitters

Electronic synapse [gap junction (nexus)]: connexin

Morphological classification (EM)

4 Histo: CNS -

Chemical Synapses Ultrastructures

Presynaptic element: synaptic vesicles (active zone)

Synaptic cleft Postsynaptic element: clustering

of receptors/channels Neurotransmitters

Chemicals: 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.

5 Histo: CNS -

Structural (EM) classification of Synapses axosomatic synapse axodendritic synapse axoaxonic synapse

Axodendritic Axosomatic Axoaxonic

6 Histo: CNS -

Neuroglia

Microglia (macrophage)

7 Histo: CNS -

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

8 Histo: CNS -

Types of neuroglia

Astrocytes (Astroglia) Protoplasmic, Fibrous Oligodendrocytes (Oligodendroglia) Microglia (Mesoglia) Ependyma cells, Choroid

epithelium

9 Histo: CNS -

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

10 Histo: CNS -

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

11 Histo: CNS -

Protoplasmic astrocyte

Blood vessel

Cajal method Silver impregnation

GFAP

12 Histo: CNS -

Fibrous astrocytes

in white matter, and periventricular gray matter

an ovoid euchromatic nucleus with pale-staining cytoplasm and long, thin processes

13 Histo: CNS -

Fibrous astrocyte

Silver-gold impregnation

Immunocytochemistry GFAP

14 Histo: CNS -

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”)

15 Histo: CNS -

Microglia

Microgliosis

Immunohistochemistry: MHCII (major histocompatibility complex II) for

activated microglia Silver impregnation

16 Histo: CNS -

Oligodendrocytes

Form myelin sheath in CNS Smaller size than astrocytes Small irregularly shaped

deeply stained nucleus Various classifications and

Types Perineural

oligodendrocytes Perifascicular

oligodendrocytes

17 Histo: CNS -

Perineuronal oligodendrocytes

Mainly in gray matter Closely associated with

soma of neurons ? Functions: metabolic

interdependency oligo

18 Histo: CNS -

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

19 Histo: CNS -

Perineuronal oligodendrocytes

Perifascicular oligodendrocytes

Oligodendrocytes

19

20 Histo: CNS -

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.

Different patterns of myelination between CNS and PNS: 1/3

21 Histo: CNS -

3. One Oligo for several axons; One Schwann for a single axon 4. Distance between cell body and myelin sheath: Oligo >

Schwann

Different patterns of myelination between CNS and PNS: 2/3

22 Histo: CNS -

5. Basal lamina associated with myelin sheath: (-) in CNS, (+) in PNS

6. Supporting connective tissue for myelinated axons: (-) in CNS, (+) in PNS

Different patterns of myelination between CNS and PNS: 3/3

23 Histo: CNS -

Demyelinating diseases (脫髓鞘疾病)

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

24 Histo: CNS -

Guillain-Barré syndrome (GBS)

Day 1 Lower limbs

Day 3 Upper limbs

Day 7 Respiratory failure

Progressive weakness

25 Histo: CNS -

Ependymal cells Lining cells of ventricular system Ventricles Aqueduct Central canal Choroid plexus: continuous with ependyma cells of ventricles

26 Histo: CNS -

Ependymal cells: Glia with Epithelial characters

27 Histo: CNS -

Ependymal cells

C: cilia M:microvilli JC: junctional complex BB: basal body G: Golgi apparatus

28 Histo: CNS -

Choroid plexus Ependyma layer + vascular core

(fenestrated vessels + loose connective tissues)

Produce cerebrospinal fluid (CSF) Blood-CSF barrier

29 Histo: CNS -

Blood-Brain Barrier (BBB)

Nonfenestrated (continuous type) endothelial cells (tight junction)

thick basal lamina with outer surfaces enclosed by

Astrocyte foot processes (perivascular feet, end feet)

30 Histo: CNS -

Blood-Brain Barrier Capillary of continuous type; Thick

basal lamina; Perivascular feet Functions: impermeable to foreign

substances for preventing Autoimmune damage

Blood vessel

31 Histo: CNS -

Meninges Dural mater

(pachymeninx) periosteum of

skull subdural space

Pia-arachnoid (leptomenginges) Arachnoid mater subarachnoid

space / cistern Intact vessels

Pia mater

32 Histo: CNS -

Meninges

33 Histo: CNS -

Pia-Arachnoid

34 Histo: CNS -

Organization of CNS Cerebellum: 3 layers Cerebral cortex (Neocortex): 6

layers (cytoarchitecture: Broadmann area)

35 Histo: CNS -

Cerebellum

Mol: molecular layer Pkj: Purkinje cell layer Gr: granular layer

Cerebellar cortex

36 Histo: CNS -

Pyramidal cells (neurons)

37 Histo: CNS -

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

38 Histo: CNS -

Response of a nerve to injury

39 Histo: CNS -

Nerve Degeneration and Regeneration

40 Histo: CNS -

Nerve injury: PNS vs. CNS

41 Histo: CNS -

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.

42 Histo: CNS -

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