CNS and PNS Flashcards
White matter
- outer part of the spinal cord but inner part of brain
- contains ascending and descending myelinated (myelin coats axons) nerve fibers
- fibrous astrocytes + glial cells
- divided into 3 parts; ant, lat and post funiculi
- NO cell bodies of neurons
Gray matter
-inner part of the spinal cord and brain cortex
- cell bodies of the neurons (PERIKARYA)+ their dendrites, glial cells; protoplasmic astrocytes, microglia and oligodendrocytes
- vascularized
- divided into ant, lat, post columns/horns
- central gray commissure with a central canal lined with ependymal cells (neuroepithelial multicilliated cells that line the spinal cord and the cerebral ventricles; derived form the radial glial cells)
NS cells
nerve cells (neurons) - reception, transmission, processing stimuli
glial cells - supporting - insulation, nutrition and protection
staining methods
Nissl’s (nissl;s bodies) - motorneurons , Luxol blue, Weigert’s method (myelin sheath)
silver impregnation - neurons, neurofilaments, glial cells
immunohistochemistry - neurotubules, neuroglia (intermediate filaments of the astrocytes composed by the GFAP)
Meninges
- periosteum
- epidural space (at vertebral column)
- dura mater (dense CT)
- subdural space
- arachnoid (CT w squamous cells)
- subarachnoid space (CT trabeculae, cerebrospinal fluid, vessels)
- pia mater (loose CT + vessels)
- memebrane limitans glliar superficialis
Cerebral cortex
- formed by grey matter
-CYTOarchitecture - describes the appearance of the NEURONS in diff parts of the cortex
-MYELOarchitecture - shows the arrangement of the nerve fibers in the cortex
cytoarchitecture
- molecular layer - nerve fiber, glial cells, neurons - horizontal cajal
- outer granule layer - small neurons (10um) and star shaped
- outer pyramidal layer- pyramidal neurons (40um) - apical dendrites and basal axons
- inner granule- small neurons and star-shaped
- inner pyramidal layer - large pyramidal cells = Pyramidal cells of BETZ (100um)
- multiformis/polymorphic cells - diverse shapes; fusiform, angular and Martinotti cells (multipolar cells)
myeloarchitecture
- Exners band
- Bechterv;s band
- outer baillargers band
- inner baillargers band
- Meynert’s band
- radial fibers
Types of neurons
pyramidal n
horizontal cells of cajal
Martinotti cells
basket n.
stellate n.
fusiform n.
glialforming stellate cells
Cerebellum
grey matter - cortex = folia separated by sulci
white matter - medulla = arbor vitae
3 Layer
1. molecular layer;
- basket and stellate cells
- dendritic ramification of the purkinje cells
- axons of small granule cells
- dendrites of large granule cells
- climbing fibers*
- stratum gangliosum
- bodies of the purkinje cells
- baskets axosomatic synapses - stratum granulosum
- small granule cells (5-6um) + dendrites
- large granule cells (8-10um) + axons
- mossy fibers* Bergmann glial cells
- cerebellar glomeruli (synaptic connections between the granule cells + mossy fibers
*mossy fibers - fibers entering the cerebellum
*climbing fibers - axons of the inferior olivary nucleus
Choroid plexus
- villous processes form the pia mater to the brain ventricles.
- simple cuboidal epithelium lining
- convex apical surface with microvilli
- basal plasmalemma infolding like basal labyrinth
- LPM - loose CT and highly vascularized
*production of cerebrospinal fluid by selective ultrafiltration.
CSF
- clear/yellowish
- slightly alkaline
- adult 135 ml
- daily production = 500 ml
*similar contents as the blood plasma
PNS
- develops from the neural crest cells
composed of nerve ganglia (cell bodies of the neurons) and peripheral nerves (nerve fiber»_space;nerve fascicles»_space; nerves)
*its supporting glial cells are the satellite and Schwann cells
satellite cells - envelope the neuronal bodies to provide electric insulation and metabolic path exchange
schwann cells - myelin sheath surrounding the axon - insulation form the rapid conduction of impulses
PNS ENVELOPES
- endoneurium - nerve fiber envelope
- Axon with the schwann sheath (myelin)
- composed of loose CT - perineurium - fascicle envelope
- specialized flatten tissue cells
- contributes to the blood nerve barrier
- held by tight junction - epineurium - nerve envelope
- dense irregular CT
NERVE GANGLIA
Composed of;
- ovoid neural bodies surrounded by glial satellite cells
- enveloped by a dense irregular CT capsule
- sensory to CNS
- autonomic to PNS
Spinal (posterior root/ sensory )ganglia
- at the post. root of the peripheral nerve
- pseudounipolar neurons (ganglion cells); usually grouped
- a continuous layer of the satellite cells surrounding the neurons
- AFFERENT
Autonomic (peripheral motor ganglia)
- parasympathetic and sympathetic NS
- Pregnaglionic (CNS) impulse thorough axon to post ganglionic fiber of neuron –> PGS chain
- mediated by acetylcholine
- multipolar neurons; solitary (smaller than the spinal ggl)
- discontinuous layer of satellite cells around the neurons
*pale-staining nucleus and prominent nucleolus - contain lipofuscin - accumulated of residual bodies (intercellular waste of lysosomes) - stain yellow-brown
(biliruben - pigment deposits of any accumulation of metabolites)
both are non-membranous
EFFERENT
Muscle spindle
- encapsulated afferent nerve ending sending signal to the brain
- capsule , intrafusal muscle fiber (8-10), stretch receptors - about 6mm long
*(intrafusal have the nuclei centrally and myofibrils at the periphery)
*(inner capsule- periaxial space w fluid - external capsule of CT) - extrafusal muscle contracts and so does the intrafusal and is detected by the muscle spindle
- signal to the sensory afferent nerve fiber for AP
to the alpha and beta motoneurons at the spinal cord - gamma motoneurons are connected to intrafusal muscle for the sensitivity
Nerve fibers; schwann cells
NAKED
- cornea of eye or the intraepithelial.
- SHEATH BUT NOT MYELINATED
- schwann cells envelope bundle of axons + glisl nucl = NO rotation = mo myelination
- NO nodes of ranvier = voltage- gated ion channels - slow
Myelinated
- internodal seg of myelin sheath
- plasma memb of the schwann cell wrps around the axon and the glial nucl rotates = layers of myelin
- HAS nodes of ranvier = adjacent cells for RAPID impulses
- High in lipid (sheath) for protection
Macroglia
- Bergmann (mossy fibers)
- Muller cells (retina)
- Pituicytes (post pituirtary 0 pars nervosa)
astrocytes
- 1 for many due to extensive terminal branching
- protoplasmic - grey matter
- fibrillar - white matter
- reinforced by the intermediate filaments made of GFAP- gillia fibrillary acid protein –> acts as markers
- communicate w each other w gap junctions
ependymal
- neuroepiltilal (cuboidal/ columnar) multi-nucleated cells
- cilia; movement
- microvilli; absorption
of the CSF and produce it
- connect by junctional complexes
*NO BASAL LAMINA bur apiacl extensions to the neuropil (network of axons/dent. + fibrils)
oligodendrocytes
myelin sheath for electrical isolation
1 per many axons
Microglia
the defense mechanism of the CNS (phagocytosis + precursor is monocyte - bone marrow)
–> passes through the neuropil scans for damage + foreign organisms.
