Central nervous system Histolgy

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Central nervous system :

Central nervous system Dr Pankaj Maheria

Introduction :

Introduction Part: Brain Spinal cord Contain : Neurones Glial cells Blood vessels Macroscopically : Gray matter White matter

Histological technique to study the CNS:

Histological technique to study the CNS Technique which demonstrate nuclei, cell bodies and their cytoplasmic constituents. Like H&E , Nissl method for RNA. Myelin method, e.g. Weigert -pal or Luxol fast blue Immunohistochemical techniques Heavy metal techniques

Specific terms used in CNS:

Specific terms used in CNS Cortex Nucleus Column Tract or a fascicle Gyri and sulci : cerebrum Folia - Cerebellum

Anatomical division of CNS:

Anatomical division of CNS Forebrain Cerebral hemispheres Diencephalon Midbrain Hindbrain Pons Medulla Cerebellum Spinal cord

Spinal cord:

Spinal cord

Spinal cord: Grey matter :

Spinal cord: Grey matter Central gray mass of grey matter Shape of butterfly Ventral horns: More prominent Cell bodies of the large lower motor neurones . Dorsal horns: Much less prominent Cell bodies of small second order sensory neurone

Spinal cord : Grey matter :

Spinal cord : Grey matter Lateral horns: Cell bodies of pre ganglionic , sympathetic efferent neurons Central canal Central commissure of grey matter Ependymal cells CSF

Spinal cord: external features :

Spinal cord: external features Ventral median fissure Dorsal midline sulcus Dorsolateral sulcus Dorsal columns Ventrolateral sulcus Ventrolateral white matter

Spinal cord: white matter :

Spinal cord: white matter Ascending tracts of sensory fibers and descending motor tracts. Volume of white matter increases progressively from sacral to cervical region.

Cerebellum :


Cortex :

Cortex Folia Three layers Molecular layers Purkinje cells layers Granular cell layers

Molecular layers:

Molecular layers Superficial thick layer Lightly stain with eosin. Mainly made of nerve fibres and few cells name Stellate cells superficial part Basket cell deep part

Molecular layers:

Molecular layers Axon run parallel to the long axis of the folia Axon of basket cells from collaterals which arborize around the Purkinje cells in basket like manner.

Purkinje cells layers :

Purkinje cells layers Large flask shaped neuron Arrange in single row Very large cell bodies Relatively fine axon extending down through granular cell layers to end in deeper nuclei of cerebellum.

Purkinje cells layers :

Purkinje cells layers Extensive branching dendrite system which arborise into outer molecular layers in a transverse plane of folium. Dendrites synapse with axon of granular layers and climbing fibers that ascend to molecular layers. Best demonstrated by heavy metal methods.

Molecular layers :

Molecular layers Satin deeply with hematoxyline Densely packed with very small granule neurons . Golgi cells Vesicular nuclei More cytoplasm Short neuronal processes.

Molecular layers :

Molecular layers Receive impulses from Mossy fibres which end as dilated terminals in the granular layer. Glomeruli Lightly satined area Dendrites of granule cells Axon of golgi cells Terminal Mossy fibres

Cerebral cortex :

Cerebral cortex

PowerPoint Presentation:

Convoluted cortex of grey matter overlying the central medullary mass of white matter which conveys fibres between different past of cortex and to and form other part of CNS. Neocortex Sensory Motor Association cortex

Neuron type in cerebral cortex:

Neuron type in cerebral cortex Pyramidal cells Stellate cells Cells of Martinotti Fusiform cells Horizontal cells of Cajal

Pyramidal cells:

Pyramidal cells Most common type of cells Size: 10 to 120 µm Giant pyramidal cells in motor cortex known as Betz cells. Pyramidal in shaped cell bodies ,apex directed towards the cortical surface.

Pyramidal cells:

Pyramidal cells Axon: A slender Arise from base of cells Passes into underlying white matter ,though in the case of small superficially located cells, the axon may synapse in deep layers of cortex.

Pyramidal cells:

Pyramidal cells Dendritie From apex Thick branching Passes towards the surface where it has an array of fine dendritic branches Short dendrites arises from edge of the base and ramify laterally.

Stellate (granule) cells:

Stellate (granule) cells Small neurons Short vertical axon Several short branching dendrites Subtype : Basket Neuroglia Routine histology method ,the cell look like small granule

Cells of Martinotti:

Cells of Martinotti Small polygonal cells Dendrites: Few short Axon: Extends towards surface Bifurcate to run horizontally , in superficial layer.

Fusiform cells :

Fusiform cells Spindle shaped cells Right angle to surface of cortex Axon: Arises from side of body Passes superficially. Dendrites: Each end of body Branching into deeper and more superficial layers.

Horizontal cells of Cajal:

Horizontal cells of Cajal Small and spindle shaped Oriented to parallel to surface. Least common cell type Only found in the most superficial layer where their axon pass laterally to synapse with dendrites of pyramidal cells.

Layers of neocortex :

Layers of neocortex Plexiform (molecular) layer Outer granular layer External pyramidal cell layer Inner granular layer Internal pyramidal cell layer ( Ganglionic layer) Multiform cell layer

Plexiform (molecular) layer:

Plexiform (molecular) layer Most superficial layer Contains: Dendrites and axons of cortical neuronse making synapses with one another Spare nuclei are those of neuroglia and occasional cells of Cajal

Outer granular layer:

Outer granular layer Thin layer Dense population of small pyramidal cells and stellate cells Various axons and dendritic connection from deeper layers

External pyramidal cell layer:

External pyramidal cell layer Broad layer Pyramidal cells of moderate size Increase in size in deeper layer Martinotti cells also present. Outer band of Baillarger

Inner granular layer:

Inner granular layer Desenly packe stellate cells

Internal pyramidal cell layer (Ganglionic layer):

Internal pyramidal cell layer ( Ganglionic layer) Large pyramidal cells and smaller number of stellate cells and cells of martinotti Inner band of Baillarger

Multiform cell layer :

Multiform cell layer Wide variety of differing morphological forms Contains: Small pyaramidal cells Cells of Mortinitti Stellate cells especially superficially Fusiform cells in deeper part

White matter:

White matter Contains incoming and outgoing nerve fibers

Ganglia :

Ganglia Oval bodies made of aggregation of cell bodies of neurons outside the CNS. Serve as relay centers in the neuronal pathway Epineurium : Dense connective tissue covering the ganglia Satellite cell: A layer of cuboidal cells covering the cell bodies of the neurons. Function : structural and metabolic support Embryological origin from neural crest Type: Sensory Motor

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Sensory ganglia (Somatic ) Motor ganglia (Autonomic) Pseudo unipolar neurons Large rounded and of varying size Nucleus : centrally placed Found in groups Multipolar neurons Small ,angular and of uniform size Nucleus: eccentrically placed Found scattered Well define satellite cells Poor define satellite cells Example : spinal ganglion Example : sympathetic ganglion

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Exercise :

Exercise Differences between sensory and motor ganglia? Draw diagram of distribution of cell types in layers of cerebral cortex. Draw diagram of distribution of cell types in layers of cerebellar cortex.

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