Microscopic structure – practice 2013 89. Nerve tissue Microscopic structure – practice 2013

Nerve tissue - morphology cells : 1.neurons and 2.glial cells extracellular material is extremely reduced replaced by glial branched process neuropil – high amount of synapses, dendrite´s arborisation, non-myelinated axons extensive vasculature with variable amount of connective tissue both in CNS and PNS blood-brain barrier in CNS

Tissue microscopic structure: cells with processes – integrated communicating network neuron theory – contact junctions among neurons

NEURON is structural and functional unit of nerve tissue N3 – cerebellum,HE NEURON is structural and functional unit of nerve tissue

Nerve tissue microstructure (example 2 – brain ) Glial c. Neuron

Perikaryon (soma, cell body) receptor region, integration, trophic centre nucleus large, lightly basophilic, with dispersed chromatin, prominent nucleolus RER abundant → substance of Nissl - tigroid Golgi apparatus only in perikaryon! cytoskeleton (neurofilaments) mitochondria inclusions lipofuscin, melanin

Cytoskeleton Microtubules axonal transport (anterograde, retrograde, microtubule-associated motor proteins used ATP – dynein, kinesin) shape regulation Neurofilaments (intermediate filaments in neurons) resistance against deformations regulatory process Microfilaments (aktin)

Dendrites receptor region principal recieving site arborisation (branching) increases receptive area of the cell (100 000 contacts and more) dendritic spines (site of synapse - postsynaptic membrane, actin microfilaments neurofilaments (NF-L, NF-M, NF-H), other cytoskeleton units, proteosynthetic apparatus except GA always non- myelinated

Axon conductive region transmit stimuli in the form of action potential to other neuron or effector cell 1 neuron has 1 axon metabolically dependent on perikaryon Golgi type I neurons – motor neurons of CNS with long axon (up to 1 meter) terminate on skeletal muscle Golgi type II neurons – short axons axon hillock, initial segment – site of action potential generation axonal transport transport vesicles, mitochondria , proteins…by anterograde x growth factor, viruses..by retrograde

Synapse effector region, unidirectional transmission of nerve impulse presynaptic (axonal) terminal + postsynaptic (dendritic, somatic, axonal) membrane site of chemical message transmission in response to action potential presynaptic : synaptic vesicles with neurotransmitters, microtubules+kinesin, mitochondria synaptic cleft 40nm postsynaptic membrane of effector cell: nerve cell muscle cell secretory cell axodendritic,axosomatic,axoaxonal, „en passant“

Neuroglia supporting sell population for neurons provide neurons with structural support and maintain local condition for neuronal function forming 50% volume of CNS 10 x more abundant than neurons histological staining impregnation by Ag, Au salts, histochemical technics

Glia - types in CNS 1. macroglia astrocytes oligodendrocytes ependymal cells 2. Microglia in PNS Schwann cells Satelite cells

Neurons and neuroglia are cells with processes

B45 Brain/Cerebrum LFB, luxol fast blue, myelin staining

B44 Brain/ Cerebrum (HE)

Neuron, neuroglia, blood vessel

N3 - cerebellum HE Purkyňova buňka Granulární neuron

B46 Small brain, cerebellum HE

Spinal cord / cross section - B48

B48 Spinal cord HE

Ependym epitheloid arrangement of ependymal cells neural tube neuropithelium remnant

B49 Autonomic ganglion

B50 Peripheral nerve

Peripheral nerve

Myelinated nerve fibres Eg 13 - Myelinizovaný axon

Myelinated nerve fibres in PNS: axons are invaginated into cytoplasm of enveloping Schwann cell (sheath is formed by layers of modified cell membranes) x in CNS: cell process of oligondrocytes form sheath nodes of Ranvier and internode, 1-2 mm Schmidt-Lanterman´s incisures

Nerve fibres axons provided by special connective tissue capsules of ectodermal origin axons: unmyelinated myelinated

Astrocytes (protoplasmic, fibrous) the largest of neuroglia astrocytic end feet- connection to vessels and neurons providing movement of wastes and metabolites to and from neuron regulate ionic concentration in intercellular space contribute to blood-brain barrier (together with tight junctions of endothelal cells) mechanical support of neurons proliferation - glial scar glial fibrillary acidic protein

Oligodendrocytes smaller, ↓intermediate fibres, darker nucleus formation of myelin sheath myelinisation of several axons

Microglia the smallest, dark elongated nucleus they migrate to the sites of dead cells, proliferate, phagocytes (dead cells, cell debris…) mesoderm -derived

Ependym epiteloid arrengement uspořádání remnant of neuroepithelium of neural tube * secretory elements (cerebrospinal fluid) component of choroid plexus of brain ventricles and central canal of spinal cord

Unmyelinated nerve fibres

N8 – Ganglion HE Satelite cells Neuron

Arrangement of nerve tissue in the body, CNS and PNS clusters of neurons – cell body: layers, columns (grey matter) bundles of axons: tracts, fasciculi, lemnisci (white matter) (grey and white matter differentiation: according to the content of myelin) PNS clusters of neurons: ganglia bundles of axons: cranial spinal peripheral nerves