The Nervous system

The Nervous system

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CommunicationNearly all multicellular organisms have communication systems.Specialized cells carry messages from one cell to another so that communication among all body parts is smooth and efficient.Communicate to maintain homeostasisThere are two systems used for communication in your body:The nervous system controls and coordinates functions throughout the body and responds to internal and external stimuli with the use of nervesThe endocrine system performs a similar function with the use of hormones

5Nervous ResponseStimulus: any change that results in a change in the organism.temperature, light, pressure, sound, smell, etc.Response: any action resulting from a stimulus.contraction of muscle cellssecretion by a glandstimulation of another nerve fiber.NeuronsMessages carried by the nervous system are electrical signals = impulsesNerve cells that transmit impulses = neuronsSensory neurons: carry impulses from sense organs to the spinal cord and brainMotor neurons: carry impulses from the brain and spinal cord to muscles and glandsInterneurons: connect sensory and motor neurons and carry impulses between them

Parts of a NeuronCell body = largest part containing nucleus and cytoplasm (most metabolic activity occur here)Dendrites = short, branched extensions spreading out from the cell body and they carry impulses from the environment or other neurons towards the cell bodyAxon = long fibers that carry impulses away from the cell body and ends at the axon terminal

Axon terminalsMyelin sheathNodesCell bodyAxonNucleusDendritesSection 35-2A Neuron

NervesNeurons bundle together to form nervesSome nerves may be only a few neurons, and others may be hundreds or thousandsThe myelin sheath may insulate axons by surrounding itThere may be some gaps in the myelin sheath called nodesImpulses jump from one node to the next, increasing the speed impulses travelResting NerveNerve impulses are electricalThe electric potential is created as the result of a sodium - potassium pump It uses ATP to pump sodium ions (Na+) out and potassium ions (K+) in = active transportThis results in a negative charge inside the cell membrane and positive charge outside = resting potentialNerve ImpulseAn impulse begins when a neuron is stimulated by another neuron or by the environment.An impulse causes positively charged sodium ions to flow in temporarily reversing the charge of the cell membrane = action potentialAs the impulse passes, positively charged potassium ions flow out and the charges restore to the normal resting potential

At the leading edge of the impulse, the sodium gates open. The membrane becomes more permeable to Na+ ions and an action potential occurs.As the action potential passes, potassium gates open, allowing K+ ions to flow out.The action potential continues to move along the axon in the direction of the nerve impulse.At rest.Action PotentialAction PotentialSection 35-2Figure 35-7 An ImpulseAction Potential

SynapseAt the end of the neuron, the impulse reaches an axon terminal where the impulse may be passed along to another neuron or another cellThe location where a neuron can transfer an impulse to another cell = synapseThe synapse is a small gap that separates the axon terminal from the dendrites of the next neuron or another cellThe terminals contain tiny sacs or vesicles filled with neurotransmitters = chemicals used by a neuron to transmit an impulse across a synapseThe neurotransmitters stimulate the next neuronThe impulse will continue with the stimulation exceeds the cells threshold

VesicleAxonAxon terminalSynaptic cleftNeurotransmitterReceptorDendrite of adjacent neuronDirection of ImpulseSection 35-2Figure 35-8 The Synapse

Reaction activityReaction time = the amount of time required for an impulse travel from your sensory neurons to your motor neurons

The Nervous SystemNeurons work together forming the nervous systemThere are two major divisions of the nervous system:Central nervous system (CNS)Peripheral nervous system (PNS)Parts of the Nervous systemCentral nervous system (CNS):Brain Spinal CordPeripheral nervous system (PNS):Sensory divisionMotor divisionSomatic nervous systemAutonomic nervous system

Central Nervous SystemThe CNS is the control center of the body:Relays messagesProcesses informationAnalyzes information

Brain and Spinal cordBoth are protected by bonewrapped in 3 layers of connective tissue = meningeslayers may have a space between them filled with cerebrospinal fluid which protects (shock absorber) and exchanges nutrients and waste

BrainAbout 100 billion neurons, mainly interneuronsMajor parts of the brain:Cerebrum CerebellumBrain stemThalamusHypothalamus

PonsPituitary glandHypothalamusCerebrumMedulla oblongataSpinal cordCerebellumPineal glandThalamusSection 35-3Figure 35-9 The Brain

Cerebrum Cerebral CortexCoordinatesThinking and learningCreativityFive sensesMemory and emotionProblem-solvingDecisions

http://www.morphonix.com

CerebellumCoordinatesMost musclesMovementLearned skillsBalance

http://www.morphonix.com CerebellumReceives messages from most of the muscles in your bodyCommunicates with the other parts of the brainSends messages about movement and balance back to your body

http://www.morphonix.com Brain StemCoordinatesHeartbeatBreathingDigestion SwallowingBlinking

http://www.morphonix.com ThalamusReceives messages from the sense organs and relays the information to the cerebrumhypothalamusActs as a control center for recognition and analysis of hunger, thirst, fatigue, anger, and body temperatureSpinal CordLinks communication between the brain and the rest of the body31 pairs of spinal nerves branch out from the spinal cord connecting brain to bodyReflexes = quick, automatic responses to stimuli are processed directly in the spinal cord

Spinal nerveCentral canalGray matterWhite matterMeningesSection 35-3Figure 35-11 The Spinal Cord

http://www.merck.com

http://www.paraquad.asn.au/ Peripheral Nervous SystemConsists of nerves and associated cells that are not part of the brain or spinal cordReceives information from the environment and relays commands from the CNS to organs and glandsDivided into two parts:Sensory division: transmits impulses from sense organs to the CNSMotor division: transmits impulses from the CNS to the muscles or glandsPNS animation (Pain receptor) : http://pennhealth.com/encyclopedia/em_DisplayAnimation.aspx?gcid=000054&ptid=17 Somatic SystemPart of motor division that regulates activities that are under conscious control (movement of skeletal muscles)Some reflexes too What is a Reflex?A reflex is an involuntary behavior. Reflexes are usually coordinated in the spinal cord not the brain.They are present from birthThey are automaticThey are meant to protect the bodyExamples:blinking (keeps your eyes hydrated)pulling your hand away when you touch something hot.changing pupil size as you move from dark to light.Receptors & EffectorsReceptor: a specialized nervous tissue that is sensitive to a specific stimulus.nerve cells in skineyesearstaste budsEffectors: the part/s of the body that respond muscles or glandsReflex ArcThe pathway that an impulse travels:1. from the sensory receptor 2. up the sensory neuron 3. over the synapse 4. to the spinal cord (interneuron) 5. over another synapse 6. back down the motor neuron 7. to the effector

Reflex arc animations: 1. http://www.sumanasinc.com/webcontent/animations/content/reflexarcs.html2. http://msjensen.cehd.umn.edu/1135/Links/Animations/Flash/0016-swf_reflex_arc.swf Autonomic SystemPart of the motor division that regulates activities that are automatic or involuntary (heart beat and smooth muscle in digestive system and blood vessels)Two parts that have opposite effects on the organs they control:Sympathetic (gas pedal), speed up body systems; fight or flightParasympathetic (brake), slow down body systems. rest or repairConcept Mapwhich consists ofis divided intothat make upwhich is divided intoSection 35-3The Nervous SystemSensory nervesMotor nervesAutonomic nervous systemSomatic nervous systemCentral nervous systemPeripheral nervous systemSympathetic nervous systemParasympathetic nervous systemSensory ReceptorsNeurons that react directly to stimuli from the environment and send impulses to other neuron and CNSLightSoundMotionChemicalsPressureChanges in temperature Sense organsSensory receptors are concentrated in the sense organs:EyesEarsNoseMouthSkin Types of Sensory receptorsSensory receptors within each organ enable it to respond to particular stimuli. The five general categories of sensory receptors are:Pain receptorsThermoreceptorsMechanoreceptorsChemoreceptorsPhotoreceptors

The 5 SensesSeeHearSmell TasteTouchSee (Vision)Photoreceptors = sense light

Hearing and BalanceSound = vibration in air detected by mechanoreceptors

Balance = As head moves, fluid shifts and hair cells bend and send impulses to the CNS to determine body motion and position

SmellSmell = ability to detect chemicals detected by chemoreceptors in nasal passageway and send impulses to CNS through sensory nerves

TasteHow food tastes is strongly influenced by smellTaste = ability to sense chemicals by chemoreceptors in taste buds mostly on tongue (sweet, sour, salty and bitter sensitivity is different on different parts of tongue)

TouchSkin = largest sense organ containing pain receptors, thermoreceptors, and mechanoreceptors

Senses activityDifferent parts of skin have different sensitivity because theres a different numbers of receptors at different locationsProblemsDrugs = substance that changes the structure or function of the bodyDrugs can interfere with the action of neurotransmitters at the synapse, which can disrupt the functioning of the nervous systemStimulantsIncrease the actions regulated by the nervous system by increasing the release of neurotransmitters at synapses (increase heart rate, blood pressure, and breathing rate)AmphetaminesCocaineNicotineCaffeine DepressantsDecrease the actions regulated by the nervous system (lowering heart rate, breathing rate, blood pressure, relaxing muscles, and relieving tension)AlcoholTranquilizers AlcoholOne of the most dangerous and abused depressant drug that slows down functioning rate of CNSFetal alcohol syndrome (FAS) = a group of birth defects caused by the effects of alcohol on the fetus (heart defects, malformed faces, delayed growth, and poor motor developmentAlcoholism = disease of people who have become addicted to alcoholCauses damage to liver where alcohol is broken downAddictionsSome drugs that act on neurons of the pleasure centers of the brain can produce an addiction = an uncontrollable craving for more of the drug or dependence on a drugCocaine causes sudden release of the neurotransmitter dopamineOpiates mimic natural endorphins to overcome painMarijuana produces temporary feeling of euphoria and disorientationDrug abuse = using any drug in a way that most doctors couldnt approveSection 35-5Commonly Abused Drugs

Used to increase alertness, relieve fatigue

Used to relieve anxiety, irritability, tension

Used to relieve painStimulants

Depressants

OpiatesAmphetamines

BarbituratesTranquilizers

MorphineCodeineIncrease heart and respiratory rates; elevate blood pressure; dilate pupils; decrease appetite

Slow down the actions of the central nervous system; small amounts cause calmness and relaxation; larger amounts cause slurred speech and impaired judgement

Act as a depressant; cause drowsiness, restlessness, nauseaDrug TypeMedical UseExamplesEffects on the body