P&a unit 4 nervous system

I. Intro – 2 parts to Nervous SystemA. Central Nervous System – CNSBrain and spinal cordB. Peripheral Nervous System – PNSAll the nerves that connect to CNS and other body parts

II. Nervous TissueA. Neurons1. Def: Nerve cell – structural and functional unit of the nervous systemB. Neuron Structure1. cell bodyMain portion of neuronContains neurofibrilsConatains NISSIL BODIESMake proteinContains nucleusMature neurons cannot reproduceDESTROY THEM AND THEY ARE GONE!!

2. dendritesShort, highly branched parts off of cell bodyEach neuron may have manyF: main RECEPTIVE surface of neuronCommunicates with other neurons**BRINGS IMPULSES IN

3. axonAn extension of the cell body which sends impulses AWAY from the neuronSchwaan cellsCells which surround axonMake up myelin (lipoprotein) sheathMS – makes impulse travel very quicklyA). Not all axons are myelinatedGRAY MATTERDef: group of cells in NS which are unmyelinatedWHITE MATTERDef: group of cells in NS which ARE myelinatedNodes of RanvierDef: narrow gaps in myelin sheath b/n axon cells

III. Nerve Impulse ConductionA. Nerve impulseDef: the propagation (increase/transmission) of electrical charges along nerve cellsB. Process of Conduction1. nerve fiber develops resting potentialDef: state in which a net POSITIVE charge is on the OUTSIDE of the cell membrane = POLARIZEDCause: Na+ and K+ are key ions3 Na+ ions diffuse outside the nerve fiber – low to high conc.2 K+ ions diffuse inside the nerve fiber – low to highWhat is the charge? POSITIVE on OUTSIDE = resting potential

2. Threshold stimulus is receivedMinimal stimulus needed for a nerve to fireWill be reached if a nerve is stimulated by:Nearby nerve stimulusChanges in light, temperature, pressureResting potential decreases – net positive charge on outside of membrane decreasesHow?Sodium/Potassium pump = active transportNa+ channels open and Na+ starts flowing inside (L to H) cell membrane = DEPOLARIZEDIf stimuli are strong enough, THRESHOLD STIMULUS is reached

3. Shortly after, K+ diffuses outside of cell (L to H) causing the cell to be REPOLARIZED4. Action potential occursDef: rapid depolarization and repolarization of a nerve cellLasts 1/1000 of a secondCauses electric current to flow to next area of nerve cell5. Wave of APs continue through nerve = IMPULSE6. refractory periodTime when nerve is repolarizing and will not respond to another stimulushttp://people.eku.edu/ritchisong/301notes2.htm

C. Impulse conduction1. unmyelinated fibersImpulses travel slowly2. myelinated fibersImpulses travel quicklyJump from N of R to N of R

D. all or none responseNerve fiber ALWAYS responds completely when TS is reachedImpulse always travels through entire nerveE. SynapseDef: the junction where 2 neurons meet and interactSending neuron: PRESYNAPTIC NEURONReceiving neuron: POSTSYNAPTIC NEURONSynaptic cleft: space b/n pre and post neurons** impulses jump this gap when traveling

F. Neurotransmitters1. def: chemical substance released by presynaptic neuron which may cause impulses to be conducted to postsynaptic neuron** if enough NT is released, TS in postsynaptic is reached and impulse travels2. TypesA. excitatory NTCause impulse to quickly be transferred to postsynaptic neuronAllows ions to quickly diffuse through membraneB. inhibitory NTCause impulse to dieTS is raised because ions can’t diffuse

ExamplesExcitatoryAcetylcholineDopamineInhibitoryGABA – gamma amino butyric acidMood, control many other excitatory NTSerotoninSlow the brain down, reduce stress, relax, effect mood

V. Types of Neurons/nervesA. Multipolar neurons – many nerve fibersMany dendrites/ 1 axonLocated: brain and spinal cordB. bipolar neurons – 2 nerve fibers1 axon/ 1 dendriteLocated: eyes, nose, earsC. unipolar neuron – 1 nerve fiber, splits into A and D1 dendrite/ 1 axonAxon connected to brain/ spinal cordDendrite connected to peripheral body part

D. Nerve typesNerves: group of neurons held together by connective tissue1. sensory nervesSend messages to brain/SC2. motor nervesSend messages to muscles/glands3. mixed nervesSend messages to both4. interneuronsConnect nerves in brain/SC

VI. Nerve pathwaysA. reflex arc1. def: the simplest pathway an impulse may take** never reaches the brainProcess:1. Sensory receptor at end of sensory nerve fiber takes in stimulation2. SNF takes it to reflex processing center in Spinal Cord3. interneurons communicate in SC4. motor neuron carries response to effector5. effector does action – muscle, gland etc

B. reflex behavior1. def: automatic unconscious responses to changes occurring within or outside the body2. controls: Heart rateBreathing rateBlood pressureDigestionSneezingCoughingVomiting

3. example: knee jerkA. sensory receptor sense touch to petallar ligamentB. sensory nerve fiber dendrite takes in infoC. impulse sent to SC where sensory axon meets an interneuron which connects to motor neuron dendriteD. motor axon carries impulse to effector in quadE. quad flexes 4. withdrawal reflexPerson touches something hot, pulls away body partP. 214

VII. Impulse processingA. convergence1. def: neuron impluses from 2 or more axons converge on 1 neuronAllows NS to bring different information togetherB. divergence1. def: impulses leaving 1 axon pass into several other neuronsAllows impulse effect to be amplifiedEx: send message to all motor neurons in muscle so all contract

VIII. Coverings of CNSA. Intro1. brain lies in: cranial cavity2. SC lies in: vertebral canal3. both surrounded by membranes called MENINGESBetween bone and nerve tissue

B. meninges3 layersDura materArachnoid materPia mater1. dura materOutermostTough, white connective tissueMany vessels & nervesMay extend into lobes of brain

2. arachnoid materThin, weblikeMiddle layerNo blood vessels** Cerebrospinal fluid between arachnoid and pia mater – CSF3. pia materThinInnermostMany vessels to nourish brain and SC

VIII. Spinal CordA. IntroCord begins at foramen magnum and end at intervertebral disk b/n 1st and 2nd lumber vertebraeB. structure1. 31 segments, each with a pair of nerves that branches off peripherallySpinal nerves8 cervical12 thoracic5 lumbar5 sacral1 coccygealCAUDA EQUINA – last group of nerves, taillike

3. Functions of SC1. to conduct nerve impulses to and from BrainInvolves only white matterA. ascending tractCarry impulses TO brainB. descending tractCarry impulses FROM brain to muscles/glands2. to be the center of the reflex arcInvolves grey matter

IX. BrainA. Intro100 billion multipolar neurons3 major portions:1. cerebrumLargestNerve centers for sensory and motor functionsMemory and reasoning centers here2. cerebellumPosterior/dorsal regionCoordinates complex skeletal voluntary muscle movementsMaintains posturePosition of body parts3. brain stemConnects nerve pathways that connect many nerves between SC and brainRegulate many organ activities

B. Cerebrum1. StructureA. cerebral hemispheres (2)2 equal halves of cerebrumB. corpus callosumBridge of nerve fibers that connects cerebral hemisheresAllows R and L sides to communicateC. convolutionsRidges of cerebrumD. sulcusGroves b/w convolutionsE. fissuresDEEP groves b/n parts of the brain

F. frontal lobeG. parietal lobeH. occipital lobeI. Temporal lobeJ. cerebral cortexThin layer of grey matter over cerebrumCovers convolutions, sucli, and fissuresContains nearly 75% of all neuron cell bodiesJust beneath is a mass of White Matter that makes up cerebrum

2. functionsA. frontal lobe1. motor speech area – Broca’s AreaMoves mouth, tongue, pharynx, larynx2. frontal eye fieldControls voluntary movements of eyes and eyelids3. Concentration, planning, problem solving area4. emotions and reasoning5. motor areas which control voluntary muscles

B. parietal lobeSensory areas involved with sensations of skinUnderstanding speech, using wordsC. occipital lobeVisual areaCombines visual images from L and R eyesRecognitionD. temporal lobeInterpretation of sensory experiencesMemory of visual and audio patternsE. general interpretive areaOverlaps all lobesPrimary in complex thought and processingF. hemisphere dominanceL= verbal, analytical, computational, detailedR= musical, visual, creative,

C. cerebrospinal fluid – CSF1. structureA clear liquid that is secreted by CHOROID PLEXUS in pia materTiny flowerlike massesCirculates around the brain and down central canal of SC – eventually reaches blood to deliver wastes etc2. functionSurrounds brain and SC for support/protectionProvide path to blood for waste** always stays at same pressure b/c it is continually made and reabsorbed** it not, pressure on the brain

D. cerebellum1. located below occipital lobe2. mostly white matter3. covered by CEREBELLAR CORTEX – grey matter4. involved in:PlanningPersonalityIntelligenceInterprets desired movements and causes body to do them5. damage = :TremorsLoss of muscle toneUncoordinated walkLoss of equilibrium

E. brain stemDef: bundle of nerve tissue that connects cerebrum to spinal cordSeveral masses of grey matter1. Parts:A. diencephalonb/w cerebral hemispheres1) infundibulum hereA piece which hangs down and attaches to pituitary gland2) thalamus hereReceives all sensory impulses and relays them to appropriate region of cortex for interpretation

3) hypothalamus hereRegulates heart rate, blood pressure, body temp, hunger, release of hormones, regulates sleep4)limbic system hereCombination of many areasInvolved in emotional expressionFear, anger, pleasure, sorrowRecognizes things that threaten life – “fight or flight”

B. midbrainBelow diencephalonMuch grey matter as a reflex centerVisual reflex = eyeballs move when head movesAuditory reflex = ears move close to soundC. ponsBelow midbrain – round bulgeRelay impulses all over brainEx: relays breathing rhythms to medulla oblongataD. medulla oblongataExtends from ponsControls:Cardiac center: speed or lower heart rateVasomotor center: constrict/dilate blood vesselsRespiratory center: rate/rhythm of breathing

X. Peripheral Nervous System - PNSA. def: nerves that branch out from the brain and SCSOMATIC NS: consists of cranial and spinal nerves that connect to skin and skeletal muscleAUTONOMIC NS: nerves that connect to organs/glands

B. Cranial nerves – 12 pair* go in order from front to back1. olfactory nerves (I)Sensory nervesTransmit smell impulses2. optic nerves (II)Sensory nervesTransmit vision impulses3. oculomotor(III)Mostly motor nervesTransmit impulses to: adjust lens, adjust pupil, move eyelid, move eye

4. trochlear (IV)Mostly motor nervesTransmit eye movement impulses5. trigeminal (V)MixedSensory: Transmit impulses from: tear glands, scalp, forehead, upper eyelids, teeth, lips, skin of faceMotor:Transmit impulses of chewing

6. Abducens (VI)Mostly motorTransmit impulses of eye movement7. facial (VII)MixedSensory:Transmit impulses of tongue/tasteMotor:Facial expression, tear glands, salivary glands8. vestibulocochlear (VIII)Sensory nervesTransmit impulses for equilibrium and hearing

9. glossopharyngeal (IX)MixedSensory:Pharynx, tonsils, tongue, neck arteryMotor:Swallowing, salivary10. vagus (X)MixedSensory:Pharynx, larynx, esophagus, organsMotor:Speech, swallowing, heart, glands

11. accessory (XI)Mostly motorPharynx, larynx, neck, back12. hypoglossal (XII)Mostly motorMuscles that move tongue

D. Spinal Nerves31 pairCommunicate impulses from spinal cord and arms, legs, neck, trunk

D. Autonomic Nervous SystemRegulates heart rate, BP, breathing rate, body tempRespond to emotional stress and strenuous physical activity1. sympathetic division Prepares body for emergency situationsInitiates activation and secretion of adrenaline2. Parasympathetic divisionActive during ordinary conditionsRestores body back to normal after stress

P&a unit 4 nervous system

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P&a unit 4 nervous system