Brain and spinal cord

neural tube

Nerves and ganglia (affernt and effernt nerves) 

neural crest

-The largest neuroglial cell

-star shaped, euchromatic nucleus and light cytoplasm

-many ramified processes that expand to contact blood vessels (perivascular endfeet(

-contribute to the BBB, regulating entry of substances into CNS

-structural support for CNS and proliferate to form a glial scar after injury to the CNS

-contain filamentous cytoskeletal protein glial fibrillar acidic protein (GFAP)

protoplasmic (primarily in gray matter; highly ramified, envelop neurons and synapses)

fibrous (in white matter; long slender processes with fewer branches)

-found in both white and gray matter

-dark cytoplasm, small heterochromatic nucleus, few processes

-live symbiotically with neurons

-produce CNS myelin with each cell producing myelin for several axons

-small phagocytic cells from monocytic lineage

-small soma, elongated nuceli, dark cyto, spikes in processes

-smallest neuroglial cell

-proliferate in regions of CNS injury

-cuboidal/columnar epithelial cells lining ventricles and central canal of spinal cord

-small, basally located nucelus

-ciliated tomove CSF

-choroid plexus is made of sprcialized ependymal cells and associated capillaries that produce CSF

-the outermost layer of meninges

-conposed of dense fibrous CT

-continuous with periosteim of skull/vertebra and separated by the epidural space in spinal level

-linedby simple squanous epi

-middle meningeal layer

-delicate sheet losely connected to dura mater 

-covered by simple squamous epi on both surfaces

-demonstrate trabeculae, which bridge the subarachnoid space to connect loosely with pia mater

-have arachnoid villi which protrude into the dura mater and return CSF to venous sinus

-higly vascularized innermost meningeal layer

-covered by simple squamous epi

-separated from nervous tissue by neuroglial elements

The most common type of neuron in vertebrates (motor and interneurons)

have the dendritic tree

Neurofilaments

Microtubules

retrograde: mediated by dyenin

anterograde: mediated by kinesin

Folds of pia mater which extend into the nucleus

highly vascularized with fenestrated capillaries 

secretes CSF

Has a thin layer of grey matter on the surface of the hemispheres with gyri

Functions to initiate motor responses; integrate sensory signals; association, analysis and consolidation of information to memories

divided into 6 layers

I-molecular: most superficial beneath pia mater

II-External granular- interneurons

III-External pyramidal- interneurons and pyramidal cells

IV- Internal granular- narrow band of small and larger interneurons

V-Internal pyramidal- ganglionic layer with pyramidal cells

VI- multiform- cells of various shapes (Marinotti cells)

III & V (External pyramidal and Internal pyramidal) cause efferent output

Gray matter with surface and folia

function to coordinate skeletal activity, maintain muscle tone and maintain equilibrium and balance

3 layers

1- molecular: superficial under pia mater. Unmyelinated fibers from granular layer and dendrites of purkinje cells; satellite cells and basket cells

2-Purkinje cells- these cells unique to the cerebral cortex. They have extensive dendritic trees

3-Granular: small, densely packed granule cells with regions devoid of cells (cerebellar islands). Usually contains the axons of the purkinje cells

Schwann cells- myleinators

Satellite cells: surround the body of the neurons

Dorsal roots: sensory axons from DRG entering spinal cord

Ventral roots: motor axons from motor neurons in the ventral horn heading to periphery

Cranial nerves: sensory and/or motor axons entering and exiting the brain

Peripheral nerves: formed from the union of dorsal and ventral roots

Collections of neuronal cell bodies outside the CNS

2 types: autonomic and craniospinal

motor ganglia where the pre and post ganglionic neurons of ANS synapse

located near the organs they innervate (in SCG) or in the organs themselves (parasympathetic ganglia)

multipolar cell bodies (eccentric nuclei surrounded by satellite cells)

neurons have a synapse

Function to regulate- visceral motility, glandular secretion, control of SM and cardiac musculature

Sensory ganglia associated with most cranial nerves and dorsal roots of spinal nerves (DRG)

round pseudounipolar cell bodies with central nucleus

No synapsing from sensory neurons to the CNS

Processes have morphology of axons

Referred to as thoracolumbar outflow since preganglionic cells found in these regions

The postganglionic neurons have cell bodies located in the paravertebral chain ganglia

Cranosacral outflow of preganglion cells

functions to stimulate secretion

antagonizes the sympathtic actions

The ganglia and postganglionic neuronal cetworks of the alimentary canal

Intramural ganglia in the walls of viscera and Meissner's and Auerbach's plexi

1) axodendritic synapse- functions between axon and dendrite

2)axosomatic synapse- between axon and soma 

(1 and 2 most common)

3)axoaxonic

4)dendrodendritic

1) Chemical- involve release of NTs from presynaptic to post synaptic neurons to cause AP (slight delay)

2)Electrical- movement of ions by gap junctions. The direct propogation of the AP from pre to postsynaptic neuron (no delay)

Boutons terminaux- single bulbous expansions and end of axons

Boutons en passage- swellings that occur along an axon with synapses at every expansion

Thickening of axolemma at synapse

Contains voltage gated Ca2+ channels (Ca2+ in the mito). The channels regulate the entry or release of Ca2+ at axon terminal => NT release

Thickening of axolemma in target neuron.

Contains subsynaptic web: an e- dense area resembling a desmosome

AP reaches axon terminal

Synaptic vesicles fuse with cytoplasmic membrane (presynaptic)

NT released into cleft

NT bind to receptors on post synaptic membrane

NT receptors cause bioelectric impluses through intracellular ions

AP propogated through target neuron

Major dense line: fusion sites of the inner leaflets of myelinating cell plasma membranes

intraperiod lines: sites of close contact, but not fusion of extracellular surfaces of adjacent myelinating cells

clefts of schmidt-lantermann: in PNS myelin; cone shaped discontinuties of myelin

inner mesaxon: inner fusion point of myelinating cell processes immediately adjacent to axon

outer mesaxon: outer intercellular point of apposition of membranes

thick and myelinated

long internodal regions

high conduction velocity

Smaller diameter than A fibers

thinner myelin than A

Moderate conductors of AP

unmyelinated but ensheathed by shwann cell cytoplasm

thin fiber

slow AP velocity (pain sensation)

Made by fibroblasts

1-epineurium: outermost fascia surrounding nerve. Dense CT (can be sutured)

2-Perineurium: sheath surrounding each bundle of nerve fibers. Divides nerves into fasicles. There is squamous epi at inner surface with tight junctions to prevent macromolecule movement (blood-nerve barrier)

3-Endoneurium: thin layer of reticular fibers produced by Schwann cells surrounding individual fibers

(induces cell body to respond by chromatolysis- dissolution of Nissl substance)

-degeneration of distal axonal segment: axon and associated myelin degrade and cleared by macrophages. Schwann cells proliferate to form a cellular column still attached to the effect organ

-regeneration of proximal axonal segment (only in PNS) where the segment adjacent to the lesions degenerates and is cleard. Growth at distal end begins and progresses towards Schwann cell columns. Successful if/when enters the column and interacts with effector organ

Autoimmune disorder where CNS myelin is attacked through inflammation causing plaques and demyleination

Causes death of oligiodendrocytes

Extreme skeletal muscle wasting due to loss of motor neurons in spinal cord

Fatal due to loss of respiratory muscles and resp. failure

1-bengin oligiodendrogliomas (slow)

2-malignant astrocytomas (fast)