Nervous tissue 2

CNS- brain and spinal cord PNS- all nerous tissue outside the CNS- nerves plexuses and ganglia

• nerve cell BODIES and neuroglia arranged into the cerebral cortex (folded structure), in cerebellar cortex, nuclei (collections of nerve cell bodies imbedded deep in brain) • unmyelinated

• In AXONS • myelinated cell axons with some unmyelinated • Axons short or long • long axons leave brain and enter spinal cord

gray matter-consists of nerve cell bodies and neuralgia forming nuclei white matter- myelinated/unmyelinated axons and neuralgia packing material) form bundles called tracts, fasciculi and lemnisci

-connects the CNS to rest of body

• part of the PNS • bundles of nerve cell axons that are myelinated and not • swann cells do myelination • cranial nerves= 12 • spinal nerves- 31 pairs

network of nerves

• collection of the nerve cell bodies (called nuclei in CNS) - There are sensory (dorsal root ganglia) and autonomic

• somatic motor system - skeletal muscles do movement

• autonomic nervous system aka visceral motor system - influences smooth muscle, cardiac muscle and glands

-sympathetic and parasympathetic and enteric division

• T1-L2 • called thoracolumbar outflow- connects thoracic and lumbar regions of the cord • fight or flight

• maintains homeostasis • CRANIOSACRAL OUTFLOW- think flow as in diarrhea stuff for parasympathetic • cranial outflow- connects with the brain thru cranial nerves • sacral outflow- connects to the spinal cord thru the sacral spinal nerves S2-S4

controls peristalsis and gland secretions and blood flow thru GI “brain of the gut” independent of the CNS- has own neurons

• junction between a neuron (presynaptic cell)and another cell (postsynaptic cell) • divided into morphological classes: axodendritic, axosomatic, axoaxonic • divided into electrical or chemical classes

• no common in mammals • in brain stem, retina, and cerebral cortex • have gap junctions- allows ELECTRICAL current to pass • RAPID

• most common type- the stereotypical synapse with presynaptic membrane, MITOCHONDRIA AND SER, synaptic vesicles (with neurotransmitter like Ach) • has PRESYNAPTIC DENSITY- consists of cone shaped structures that represent the active site of the synapse

active site of the synapse that is cone-shaped

narrow, extracellular space between presynaptic and postsynaptic membranes

• receptor site of neurotrans • displays POSTSYNAPTIC DENSITY- complex of proteins that is the is the binding site of neurotrans • ligand gated Na channels

1) kiss and run- vesicle binds and releases SOME neurotransmitter and goes back to active site of the presynaptic terminal and stays there waiting for next impulse 2) collapse- vesicle fuses with presynaptic membrane and releases ALL of its neurotransmitter and becomes part of the membrane

• located in the ventricles and synthesizes CSF and releases it into the ventricles • consists of folds of pia mater covered by simple cuboidal epithelium- ependymal cells (neuroglia) • ependymal cells- held together via zona occludentes • fenestrated capillaries

• hi- sodium k, cl • low protein • clear • 90% water, few lymphocytes • replaced 4 times a day • shock absorber for brain and spinal cord

-does not have lymphatic vessels so gets rid of it via difficusion into CSF into the subarchnoid space where it is reabsorbed by ARACHNOID VILLI