Week 12 & 13: Histology of Neural tissue Flashcards
Typical neuron intracellular features
extensive cell processes, a large euchromatic
nucleus (dispersed DNA), prominent nucleolis (ribosomal RNA), extensive endoplasmic reticulum (Nissl substance, protein synthesis), a well developed cytoskeleton and axonal
microtubules (rapid transport system).
What are there more of : Interneurons or Projection neurons?
Internurons - over 99%
Internurons examples
Granule cells, horizontal cells, stellate cells
Projection neurons examples
pyramidal cells , the ganglion cells of the retina
and the Purkinje cells of the cerebellar cortex.
Where are capillaries form in retina?
Inner layers of retina
What is fovea?
Only cones, raminng cell layers pushed to one side, bipolar and ganglion bodies are small
Astrocytes
In CNS. two types: ( on basis of proccesses). Fibrous (in white matter), Protoplasmic (in grey matter). Medium to small - short processes have end feet. Help mediate blood-brain barrier
Perivascular glia limitans
Astrocyte feet
Superficial glial limitans
Astrocyte feet, pia mater????
How to best see astrocytes?
Specilaised metal stains, immunological stains
Astrocyte functions
mANY- mechanical support, regulation of ion and transmitter content in interstitial space, maintenance of blood brain barrier, formation of scar tissue
Oligodendrocytes.
In CNS. small-medium. mainly in white matter, near proximal end of projection neuron axons. Have few processes - wrap around axons - form myelin sheath. One can meyelate several axons. Most axons in CNS are Unmyelinated.
WHAT CELL forms myeline sheath in CNS
Oligodendrocytes
Microglia
in CNS. small, elongated nuclei. Derive from mononuclear cells. Migratory - pass through cerebral caps to enter or leave CNS.
Microglia functions
Immunological and phagocytic role
Ependymal cells
in CNS. layer of CUBOIDAL cells - line ventricles and spinal canal of CNS. Villi and and cilia, NO basal lamina, joined by tight junctions
Choroid plexus - location and function
In LATERAL ventricles & roofs of THIRD and FOURTH ventricles. Where most CSF made.
Choroid plexus - layers
CApillary endothelium, pial cells (+loose CT), Edendyma (choroid ep).
What are the capillaries in choroid plexus?
Fenestrated.
Pia mater
SIngle layer of flatteneed cells, resting on basal lamina, small amount loose CT. Adheres to surface - follows, surrounds BV for short distance into brain. Adjacent to Basal lamina are astrocyte feet ends.
Dura mater
Inner layer - several layers of flattened cells. Thickened outer layer - CT. Contains BV. IN skull - fused with periosteum.
BV - Brain
Medium sized art + veins - in subarachnoid space. In brain - cap neetwork ++ grey mater.
Cap in CNS
Cap endothelium, basal lamina, tight junctions (most)., astrocyte feet surround + intermitteant pericytes.
Blood brain barrier
caps not fenestrated, tight junctions. edno surrounded by astrocyte feet = pervascular glial limitans. Junctions modulated by glial cells and possibly pericytes. Barrier = selective for cels and molecules. fenestrated in choroid plexus.
Somatic sensory neuron
cell body - large euchromatic nucleus, prominent nucleolus in dorsal root ganglion or cranial nerve sensory ganglion, surrounded by satellite cells. Unipolar golgi type 1.
Somatic sensory neuron - responding to ongoing stimulus
Slow, non-adaptors
Somatic motor neuron
Euchromatic nucleus, prominent nucleous, many dendrites, lone long branching axon, usually mylenated, multipolar.
Motor neurons that act on muscle spindles
Gamma motor neurons
Visceral sensory neuron
Similar or same as somatic sensic neuron. Peripheral process in splanchnic or CN, cell body + central process .
Visceral motor neuron
Pre and post ganglionic neuron. Both are multipolar and smallish. Preganglionic cell body - lateral part grey mater or CN nucleus.
Visceral motor - Symp
Thoracic and upper lumbar spinal cord segments
Visceral motor - ParaSymp
brain stem and sacal segments 2,3,4.
Postganglionic cell body location in SYMp
symp trunk, prevertebral ganglion (short pre, long post)
Postganglionic cell body location in ParaSYMp
ganglion near viscera (long pre, short post))
Difference between pre and post ganglionic autonomic neuron
Pre = myelinated. Post - un
Satellite cells
In PNS. small cells, surround cell bodies in somatic sensory and autonomic ganglia
Schwann cells
In PNS. Multiple functions. elongated cells. wrap around segment of one axon (myelinated). or have multiple axons invaginated in them (unmyelinated)
Perineural cells
PNS. flattened cells, arraranged in layers, surround collections of axons in PNs - form boundaries of the fasciles. Cells joined by tight junctions, basal lamina either side of cell layers. - produce collagen.
Cross section of typical peripheral nerve. layers
Nerve fibres, 4 layers of wrapping: Schwann cell, endoneurium, perineurium, epineurium.
Enteric Nervous system
Within submucosa (meissners plexus) and muscularis externa ( myenteric/auerbachs plexus) . Can act autonomously, but have input from autonomic, vesceral system.
