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Patho Exam 3 Neuro OutlineNervous System A&PCentral Nervous SystemBrainSpinal CordPeripheral Nervous SystemCranial NervesSpinal NervesFunctionally divided into:Somatic Nervous System – pathways that regulate voluntary motor control (ex: skeletal muscles) Think Somatic = So I’m gonna move my arm and slap you, voluntaryAutomatic Nervous System – pathways that regulate body’s internal environment via involuntary control of organ systems (ex: heart/circulatory system). Further divided into:Sympathetic Nervous System (SNS)Dilates pupils, inhibits salivation, relaxes bronchi, accelerates heart, inhibits digestive activity, stimulates glucose release by liver, secretion of epinephrine and norepi from kidney, relaxes bladder, and contracts rectum. This is the Fight or Flight response. All these things are to help you run away from bears and what not… You breathe better, see better, have glucose for energy, and don’t pee/poo while you’re runningParasympathetic Nervous System (PNS)Constricts pupil, stimulates salivation, inhibits heart, constricts bronchi, stimulates digestive activity, stimulates gallbladder, contracts bladder and relaxes rectumPathwaysAfferent PathwaysAscending – carry sensory impulses towards the cns (or ascending = away from the place where the impulse started, like you prick your finger and the impulse goes away from your finger to the brain and ascends your arm to your brainEfferent Pathways39065204899025Descending – transmit motor impulses away from the CNS (or descending = down from the brain to the arm or wherever). Basic Parts of the Nervous SystemNeuronsConsists of cell body (controls cell activity), dendrites (conduct info toward cell body), and axons (carries impulses from the cell body).Schwann CellsPNS supporting cellsWrap the nerve, create myelin sheathNeuroglia“Nerve Glue”CNS supporting cellsProvide structural support and nutritionNerve Injury & RegenerationRemember, mature nerve cells don’t divide! Once they’re damaged, they’re damaged. Injury can cause permanent loss of function. Injury can cause permanent loss of functionSevered axon → swelling in portion distal to cut → neurofilaments hypertrophy → myelin sheath shrinks / disintegrates → axon degenerates & disappearsMyelin sheaths reform into Schwann cells that line up in a column between cut & effector organProximal to cut (similar changes back to next node of Ranvier)→ swelling/disperses Nissl substance → cell increases metabolic activity / protein synthesis → 7-14 days later, new terminal sprouts project from the proximal segment & may enter remaining Schwann cell pathway (limited to myelinated fibers & generally occurs only in the PNS)Regeneration in CNS limited by ↑ incidence of scar formation & different nature of myelin formedRegeneration depends on many factors—location, type of injury, inflammatory response, process of scarringThe closer (of injury) to cell body, greater chances of cell dying/not regenerating ConsiousnessArousal + Content of thoughtArousal: State of awakeness of individual (*Reticular activating system)Content of thought: Awareness of self, environment, and responsiveness (Ex: Cognition)Alterations in ArousalCaused by:Structural damage (trauma, vascular, infection)Metabolic disturbances (hypoxia, electrolyte disturbances, drugs, toxins)Psychogenic (rare--psychiatric)PathoProcesses depend on locationDysfunction may be diffuse (Ex: Encephalitis)Dysfunction may be localized (Ex: Tumor / Mass)Traumatic Brain InjuryBlunt force/closed head traumaCoup / contrecoupCoup = primary impact, injury to the brain when the brain was originally hitCountrecoup = secondary impact, injury to the brain opposite of the site of primary injuryPathoAcceleration impact→injury to local areaDeceleration impact→injury to opposite sideHematomas may form→increased intracranial pressure (↑ICP)Edema forms around & in damaged neural tissue→ ↑ICPExtradural hematomaSubdural hematomaIntracerebral hemorrhageOpen/penetrating traumaBullets, knives, screwdrivers, etc. PathoBrain structures may be exposed to environmentInjury to brain tissue significantHigh risk for infectionS/S of Brain TraumaHeadache w/increasing severity, vomiting, drowsiness, confusion, seizure activity, respiratory depression/failure, loss of consciousness, loss of reflexes, pupil dilationSpinal Cord InjuryCause: Pulling, twisting, severing, or compressing neural tissue of spinal cordLevel of injury will determine clinical manifestations (S/S) (Ex: hyperextension/hyperflexion of neck)See pictures on p. 397 in Patho book Most common is C5-7, then L1 (tailbone) and some T’s47104306663055Peripheral Nerve TraumaCauseCrushing or cutting of neuronsS/SNumbness, parasthesia (abnormal sensation i.e. burning, prickling, tingling, tickling), painSuccess for regeneration much higher in crushing injuries Cerebrovascular DisordersTransient ischemic attack (TIA)Brief period of inadequate cerebral perfusion→sudden focal loss of neurologic functionFull recovery usually within 24 hoursCerebrovascular accident (CVA)Stroke often causes permanent neurological deficitsDamage occurs within seconds to minutes due to loss of perfusionS/S of CVADepends of brain hemisphere & location of the occurrence (remember the right brain affects the left half of the body)Loss of Consciousness, weakness, difficulty speaking, difficulty swallowing, impaired vision, parasthesiasInfectious CNS DisordersMeningitisCausesBacteria, viruses, and fungusPathoBacteria normally found in nasopharynx Usually starts w/upper respiratory infection → bacteria become blood borne →(thought to)enter CNS through choroid plexus → bacteria (or toxins) cause inflammation in meninges→ exudate causes thickening of CSF→ impedes flow, disrupts blood flow due to swelling S/STypical symptoms for infection plus:Severe headache, photophobia, nuchal rigidity, ↓consciousness, seizures, and petechial rashViral symptoms usually less severeFungal symptoms much slower & insidiousEncephalitisCausesUsually viral – mosquito borne viruses & herpes simplex 1PathoVirus reaches meninges leading to edema which increases ICP which causes widespread nerve cell degenerationS/Sfever, delirium, confusion → unconsciousness, seizure activity, involuntary movement, abnormal reflexes, paresis & paralysisAlterations in Cognition and Motor FunctionDegenerative DiseasesAlzheimer’s DiseaseInfoMost common neurodegenerative disorder / most frequent cause of dementia in elderlyExact cause unknown → ?loss of neurotransmitter stimulation“Neurofibrillary tangles” & “senile plaques” found in cerebral cortex & hippocampusS/SEarly signs mimic natural aging process (making it hard to diagnose early)Memory loss, language loss, confusion, restlessness, mood swings, difficulty in interpreting visual informationLateLoss of personality, loss of function, psychotic symptoms, and rigidity/flexion posturingParkinson’s DiseaseInfoChronic, progressive degeneration of neurons in the basal ganglia (corpus striatum)Associated with impaired motor functionOnset predominantly middle to old agePathoCause: UnknownDegeneration of nigrostriatal pathway → reduction in neurotransmitter dopamine → alters excitability of striatum & release of other neurotransmitters (acetylcholine)Neurons in substantia nigra lose pigment & characteristic black colorS/SRemember, most neural degeneration occurs before the onset of symptomsTremors (hands, arms, legs, face, and remember Smith said “booger rolling tremor”RigidityBradykinesia (slow movements) which may progress to akinesia (inability to move)Postural instability and late symptom = dementia ................
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