Nervous tissue Anatomically Central nervous system (CNS) brain and spinal cord Peripheral nervous system (PNS) - cranial, spinal, and peripheral nerves - ganglia: nerve cell bodies outside the CNS Major cell types Neuron: nerve cell Supporting / Glial cells - Schwann cells, satellite cells (in PNS) - glia/neuroglia (in CNS) Neurone / Neuron

Cell body Nucleus Cytoplasm (perikaryon) Process Axon Dendrites Axons (nerve fibers) Axon hillock Terminal boutons Dorsal root ganglia (DRG) nucleus ganglion/ganglia DRG neurons Basic neuron types Multipolar neuron

Multiple dendrites Single axons Types: Interneurons Motor neurons Sympathetic neurons Bipolar neuron

Single dendrite Single axon Types: Receptor neurons Vision Smell Balance Pseudo-unipolar neuron peripheral

Single axon (Stem process) with stem 2 branches: Central process to spinal cord Peripheral process to terminal tissues (muscle, joints, skin et al) functionally: dendrite structurally: axon Type: Dorsal root ganglia (DRG neuron) central Pseudo-unipolar neuron Neuron: ultrastructure

Rough endoplamic reticulum (rER) Nissl substance Cytoskeleton Microtubule Intermediate filaments: Neurofilaments Microfilaments: Actin Specialization of neuron/axon Cytoskeleton Axonal transport Neuron: ultrastructure rER: rough ER M: mitochondria L: lysosome G: Golgi

Microscopic methods

H & E (Hematoxylin and eosin) Nissl method Heavy metal impregnation Golgi, Cajal Thick sections / Spread preparations gold, silver: deposited in microtubules / neurofilaments Immunohistochemistry Microscopic methods: H & E Microscopic methods: Nissl method

Nissl substance: RNA in neuronal cell body and dendrite Microscopic methods: Heavy metal impregnation

Spread preparation Au-impregnation Microscopic methods: Heavy metal impregnation

(Purkinje cell of cerebellum) Thick section Ag-impregnation Au + counter stain Myelinated / non-mylinated nerves

Diameter: related to nerve conduction Myelination: myelin sheaths (saltatory conduction) Cells responsible for myelination Schwann cells Oligodendrocytes Non-myelinated nerve fibers Myelination Major dense line Intraperiod line Myelinated nerve fibers

Major dense line Intraperiod line Node of Ranvier Node of Ranvier Schmidt-Lanterman incisures Myelin compaction

Non-compact myelin Node of Ranvier (paranodal regions) Schmidt-Lanterman incisure (cleft) Compact myelin Between nodes of Ranvier (internodal regions) Schmidt-Lanterman incisures Synapse: General organization Synapse (terminal bouton) Presynaptic components Pre-synaptic membrane Synaptic vesicles (neurotransmitters): active zone Synaptic cleft Postsynaptic components Post-synaptic membrane (receptors for transmitters) Neurons / Effector cells Synapse Motor end plates

Gold method Histochemistry of Ach-esterase Motor end plates (Neuromuscular junctions)

Synaptic cleft Junctional folds Nerve fibers and connective tissue

Epineurium Perineurium Endoneurium Peripheral nervous tissues

Organization Epineurium Perineurium Endoneurium Processing of tissues Paraffin-embedded Epon-embedded, osmium- fixed F: fascicle; E: epineurium; P: perineurium A (axon); AT (adipose tissue); BNF (bundle of nerve fibers); BV (blood vessel); C (capillary); Epn (epineurium); F (fibroblast); M (myelin); NI (neurilemma); Pn (perineurium);SS (Schwann cell nucleus) Peripheral nervous tissues

P: perineurium S: Schwann cell; F: fibroblast Epn (epineurium); M (myelin); N (Schwann cell nucleus); NF (nerve fiber); NI (neurilemma); NR (node of Ranvier) Peripheral nervous tissues

M: myelinated fiber N: non-myelinated fiber S: Schwann cell nuclei F: nuclei of fibroblast Demyelination (segmental) demyelination: teased fiber preparation

absence of myelin sheaths in adjacent internode impaired saltatory conduction Dorsal root ganglion (Spinal ganglion)

Satellite cells Sympathetic ganglion

multipolar eccentric nuclei lipofuscin granules fewer satellite cells Sensory receptors Functional classification Exteroceptors: for thermal, pain etc Proprioceptors: in skeletal system Interoceptors: visceral organs Morphological classification Simple: Free nerve endings Compound (Encapsulated): Pacinian corpuscle, Meissner’s corpuscle etc Free nerve endings

Epidermis

Dermis Meissner’s corpuscles

Encapsulated nerve endings in dermal papilla for touch Pacician corpuscles

Lamellated sensory nerve endings with a capsule in subcutaneous tissue / hypodermis for vibratory stimuli Muscle spindles Skeletal muscles Extrafusal fibers Intrafusal fibers Nuclear bag fibers Nuclear chain fibers Sensory receptors around intrafusal fibers Annulospiral endings: in central non-striated portion Flower-spray ending: in striated portion Muscle spindles

N: bundle of nerve fibers C: capsule enclosing intrafusal fibers Review of PNS

Neurons Classification; Organization Myelin Compact myelin, node of Ranvier Sensory receptors Types vs Functions