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68 Cards in this Set
- Front
- Back
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nervous system general
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respond to changes in inter/exter enviro; regulates organ activities; SNS-sensory/motor to all body but viscera, sm muscle glands; ANS- consists of sym, parasym, enteric
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development of NS
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ectoderm-neural crest and plate; neural plate growth from notochord signals then invaginates to form groove, closes for form neural tube (CNS structures); neural crest forms PNS, glial cells, arachniod/pia mater
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neurons
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structural and functional unit; synapse in interaction btw nuerons/target cells; do not divide (but multipotent precursor cells in ventricular zone can generate-site of injury)
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cell body
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rER (nissle bodies), lysosomes with lipofuscin, MTs, meurofilaments; organelles in dendrites but not axon
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axon
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one per neuon; MT, NF, mito, vesicles; initial segment-generation of action potential; periaxoplasmic plaque-protein syn in large nerve terminals
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dendrite
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many/neuron; greater diameter than axons, unmyelinated, dendritic trees, characterize neruon types, NO golgi
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multipolar n
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1 axon and 2 or more dendrites; most abundant; motor; interneurons, pyramidal cells of cerebrum, purkinje cells of cerebellum
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bipolar n
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olfactory bulb, vestibular and auditory
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sensory neurons
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DRG: 1 axon to periphery and other to CNS; somatic: pain, temp, touch, pressure, pain, proprioception from surface; visceral: pain, etc from muscous, glands, bvs
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motor neurons
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somatic-to skeletal m; visceral: sm muscle, cardiac, glands
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axonal transport systems
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bidirectional (via MT); anterograde= cell body to periphery via kinesin; retrograde= periphery to cell body via dynein
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slow transport
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only ANTEROGRADE; structural (actin, NF, MT) and cytoplasmic matrix proteins
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fast transport
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bidirectional; anterograde= membrane organelles and low-MW materials; retrograde: same mlcs plus endocytoses materials (toxins, viruses)
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synapse terms
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boutons en passant: multiple snapses generated by travel of neuron along surface; bouton terminal: enlarged trip at end of axon
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types of synapse
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chemical-release of chemical (NT); electrical- uses ion transfer via gap junctions (sm and cardiac m)
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typical chemical synapse
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presynaptic knob- store and release of synaptic, mitocondria and presynaptic density; postsynaptic mem- receptor sites, postsyn density
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acetylchocline
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NT btw axons and striated m at NMJ; in ANS released by preganglionic sym/parasym and postsyn para; cholinergic neurons (with muscarinic and nicotineic ACh receptors); may be affected by drugs
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Catecholamines
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norepi, epi, and dopamine; CNS and PNS; tyrosine aa derivative
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Norepi and epi
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NE=postsyn sym axons (excpet sweat glands and bv-ACh), adrenergic neurons; EPI=some CNS and endocrine cells of adrenal medulla during fight or flight
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dopamine
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stimulates motor neurons; missing in parkinson's
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Serotonin/5-hydroxytryptamine
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from tryptophan; in CNS and enteric NS; serotonergic neurons; recycled by reuptake into presyn serotonergic n
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GABA, glutamate, glycine
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amino acids, mainly in CNS, GABA (inhib) and GLU (inhib)-main NT of CNS; glycine is inhib
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small peptide NT
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substance P, hypothalamic releasing hormones, enkephalins, vasoactive intestingal peptide (VIP), cholecytokinin, neurotensin; syn and released by enteroendocrine cells (also by neurosecretory of hypothalamus)
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Nitric oxide NT
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simple gas, one neuron to another; syn in synapse and used immediately, GLU activates NO synthase
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Excitatory and Inhibitory synapses
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EXC= cation channels influx of Na, depolarization of post-syn membrane, ACh, GLU, serotonin; INH= anion channels influx Cl, hyperpolarizes postsyn membrane, GABA or glycine
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membrane potential
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K leaks out but maintained by Na/K pump to exchange 3 Na for 2 K; so Na conc is high extra. and K is high intracellular; resting: when no net mvmt of K (-70mV)
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chemical synapse
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depolar opens voltage-gated Ca causing fusion of syn vesicles and NT release, bind to postsyn and opens ligandgated Na; depolar-open voltage gated Na and generate AP; Na close and K open to return to resting; depolarization sends current to repeat; firing in postsyn due to summation
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removal of NTs
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80% have high-affinity reuptake via transporters; enzymes degrade remaining 20%
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enzymes degrade NTs
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acetylcholinesterase, catechol O-methyltransferase, monoamine oxidase
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schwann cells
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support PNS; from neural crest; 1 cell myelinates 1 PNS axon, guides regrowth of PNS axons, clean up PNS debris; doesn't have to myelinate
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myelin sheath
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lipid-rich; doesn't cover axon hillock or synapse; NOR: internodal segment, external lamina, voltage reversal (cm has high conc of voltagegated Na/K exposed to extracellular space)
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satellite cells
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surround cell bodies of PNS ganglia; establish and maintain microenvir, electrical insulation, meta exchange
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enteric glial cells
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similar to astrocytes in the CNS; structure, meta, protective within ganglia of enteric ANS
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supporting cells of CNS
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oligodendrocytes (myelinates multiple axons), astrocytes (phys. and meta support), microglia (phagocytic), ependymal (line ventricles); proliferate and form brain tumors
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microglia
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immune protectors; from monocyte, vimentin IF, center from vascular system, proliferate in areas of injury, covered with spikes
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astrocytes general
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from neural tube; regulate ionic conc, BBB, covers bare areas of axons (so NT stay in cleft, remove NT too); bundles of Ifs with GFAP (glial limitans)
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2 types of astrocytes
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proteoplasmic=gray matter, processes to BL of pia mater to form glia limitans; fibrous=white matter, fewer processes, 80% of brain tumors
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oligodendrocytes
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from neural tube; myelinate multiple axons, nucleus could be far from axons
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myelin in CNS vs PNS
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no external lamina in CNS (more contact between other axons); NOR in CNS are larger, more efficiency; unmyelinated neurons in CNS not embedded in glial cell processes
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ependymal cells
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epithelium-like lining; single layer, no external lamina, basal infoldings; choroid plexus-modified ependymal, produce CSF (remove wastes), from neural tube
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matter
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gray: outer of brain; inner in spinal cord, nerve cell bodies, axons, dendrites, glial cells; white: axons plus associated glial cells
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cerebrum
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6 layers (lamina) of pyramidal neurons
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cerebellum
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3 layers of cortex (gray matter); molecular-few neurons, mostly fibrous; perkinje-single row of nuerons, inhibitory output (GABA); granule cell layer-small nuerons with dark nuclei, excit/inhib outpout
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BBB
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formed by interaction btw astrocytes (processes w/basal lamina of endothelial)and cap endothelial cells (tight junctions); mlc cross cap wall by active transport (glucose, aa, nucleosides, vitamins); O2 and CO2 cross easily; astrocyte feet maintain H2O (waterchannels aquaporin 4); no barrier in neurohypophysis/ cricumventricular organs
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drua mater
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periosteal layer and meningeal layer; channels for blood going to brain; partitions between brain; spinal cord has meningeal layer forming separate tube around canal; subdural space-blood accumulation
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arachnoid mater
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has trabeculae (loose CT fibers with fibroblasts) extending to pia mater
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pia mater
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continuous with perivascular CT sheath of bvs; fuses with arachnoid around opening for cranial and SN
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gray mater of spinal cord
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neuronal cell bodies, dendrites, axons, neuroglia
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Ventral horn
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motor nuerons, multipolar, lots of lipofuscin, efferent, myelinated axon excpet at origin and termination, divides into branches near muscle cell and forms NM synapses (motor end plates)
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peripheral nerves
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bundle of nerve fibers held with CT; sensory and motor; DRG-sensory; postganglionic=paravertebral, prevertebral, terminal ganglia
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somatic efferent
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cell bodies in brian, brainstem, spinal cord; single neuron
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visceral efferent of ANS
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2 neurons; preganglionic in CNS-synapse with postganglionic neurons in peripheral ganglia
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sensory neurons
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single neuron from ganglion to spinal cord/brainstem; cell bodies in ganglia outside CNS and in assoc with CN 5, 7, 8, 9, 10
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endoneurium
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type 3 collagen (schwann cell); fibrils parallel and around nerve fibers; few fibroblast, mast cells (only layer with immune cells), 90% of nuclei are schwann, poorly vascularized
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perineurium
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metabolically active diffusion barrier, formation of blood-nerve barrier (tight jnts), formed by squamous cells with contractile (actin), external lamina on both surfaces, pinocytitotic vesicles
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epineurium
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dense irreg CT, associated with adipose, has bv that supple nerve; only sheath with immune cells
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DRG
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large bodies arranged closely with alternating layers of nerve fibers; impulses in terminal receptor arborization of peripheral segment
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sensory receptors
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at distal tips of neurons; initiate impulse in response to stimulus; 1)exteroceptors-stimuli from external (temp, tough, smell, sound, vision) 2)enteroceptors- stimuli within body (degree of stretch of GI, bladder, bv) 3)propioceptors- simuli within body like sensation of position, tone, mvmt 4)nonencapsulated- bar axon 5)encapsulated- Messiners, pacinian, krause's end bulb, ruffini's
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Meissner's corpuscles
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in dermis (papille), light tough, degree determined by proximity of receptors
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pacinian corpuscles
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larger, pressure/coarse touch, deeper skin/joints/serous/viscera/erogenous, center has large nerve fiber that become myelinated as it exits; distortion-amped mechanical stimulus, transduced into AP
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ANS
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innerates sm/cardiac m and glandular epi; sympathetic= preganglionic axons exit CNS via ventral roots and postganglionic from latero-vertebral chain; parasym=preganglionic axons exit by CN (3, 7, 9, 10) and sacral (2, 3, 4), postganglionic near or within effector
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antagonistic sym and parasym
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sym increases cardiac muscle, parasym decreases cardiac contraction
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enteric ANS
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brain of gut, function independ. of CNS; in lamina propia, muscularis mucosae, submucosa, muscularis externa; controls motility, exo/endocrin secretions, bloodflow, immunologyic/inflamm processes; only supported by enteric glial cells (like astrocytes)
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degeneration
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anterograde: distal to injury degenerates due to interruption of axonal transport; PNS takes few days, CNS takes weeks; axon degen. by fragmentation; phagocytotic cell remove fragments (schwann or microglia, monocytes); some retrograde degen but extends only a few segments; in PNS schwann cells remain as tubular structures distally
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changes in nuerons with injury
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cell body swells, nucleus goes to peripheral, chromatolysis (loss of Nissl); observed in 1-2 days and peaks at 2 weeks; motor fiber cut-muscle atrophies
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scar formation
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PNS: CT and schwann cells from scar btw ends of injured nerve; litttle scar tissue-will regenerate; CNS: scar tissue drom proliferating glial cells will prevent regeneration (NOGO-inhib factor)
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regeneration
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PSN requires devision of schwann (need endoneurium); schwann cells dedifferentiate and secrete glial GF; schwann form cylinders to guid neurites; neurite encountering schwann cylinder will regrow it at 3mm/day (if not then it will be disorganized); neurites enter schwann tubes and guide to destination; schwann remyelinate but length is shorter
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NMJ
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NT always generates potential; exits spinal cord via ventral to skeletal m; same as chemical synapse (voltagegated Ca); release of ACh receptors; degraded by acetycholinesterase
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