Y khoa - Dược - Chapter 30: The nervous system

30The Nervous SystemLearning Outcomes (cont.)30.1 Describe the general functions of the nervous system. 30.2 Summarize the structure of a neuron.30.3 Explain the function of nerve impulses and the role of synapses in their transmission. 30.4 Describe the structures and functions of the central nervous system. Learning Outcomes (cont.)30.5 Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system. 30.6 Recognize common tests that are performed to determine neurologic disorders. 30.7 Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the nervous system.Introduction Highly complex systemControls and helps to maintain balance in all other organ systems Disorders are numerous and often difficult to diagnose and treatGeneral Functions of the Nervous SystemCentral Nervous System (CNS)BrainSpinal cordPeripheral Nervous System (PNS)Peripheral nervesSomatic nervous system (SNS)Autonomic nervous system (ANS)General Functions of the Nervous System (cont.)Afferent nerves ~ sensory information Efferent nerves ~ impulses that allow for movement or actionInterneurons – interpreters between afferent and efferent nervesApply Your KnowledgeMatch the following:___ Somatic nervous system A. Motor nerves___ Autonomic nervous system B. Governs skeletal or voluntary muscles___ Afferent nerves C. Governs respiratory and GI systems___ Efferent nerves D. Go-betweens or interpreters___ Interneurons E. Sensory nervesCEADBANSWER:Correct!Neuron Structure Functional cells of NSTransmit nerve impulses to Other neurons EffectorsCannot divideNeurogliaSupport cells for neurons Astrocytes Microglia Oligodendrocytes Neuron Structure (cont.)Neurons Cell bodyNucleus and organellesGenerates proteins and energyNerve fibers ~ extend from cell bodyNeuron Structure (cont.)AxonsOne per neuronSend nerve impulses away from the cell bodyDendrites One or more per neuronReceive nerve impulses for the neuronNeuron Structure (cont.)Schwann cellsWrap around axonsMembranes contain myelinWhite matter – myelin sheathGray matter – no myelin sheathApply Your KnowledgeTrue or False:___ Effectors are neurons.___ Neurons can reproduce.___ Astrocytes anchor blood vessels to nerve cells.___ Microglia act as phagocytes.___ Oligodendrocytes are reproductive cells.___ Repolarization is the return to the resting state.FTTFTFANSWER:They are the muscles or glands.Neurons cannot reproduce.They take part in myelin production.GOOD JOB!Nerve Impulse and Synapse Cell membrane potential - polarizedDepolarized – sodium ions move into the cellAction potential is created Repolarization Positive ions move outReturns to polarized stateNerve Impulse (cont.)Synaptic knob contains vesiclesNeurotransmitters Produced in vesiclesReleased to allow impulse transmission to post-synaptic structuresFunctions Apply Your KnowledgeWhat is the function of neurotransmitters?ANSWER: Neurotransmitters cause muscles to contract or relax, cause glands to secret products, activate neurons to send nerve impulses, or inhibit neurons from sending them.Right!Central Nervous SystemBrain and spinal cordBlood-brain barrierProtects layers of the membranes of the CNSFormed by tight capillariesCentral Nervous System (cont.)Meninges Dura mater Epidural spaceSubdural spaceArachnoid mater Pia mater Subarachnoid space ~ cerebrospinal fluid (CSF)Spinal CordDescends through vertebral canal 31 spinal segments: 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal Cervical enlargementLumbar enlargement  Spinal Cord (cont.)Gray matter Neuron cell bodies and their dendritesHornsWhite matter Myelinated axons Funiculi Central canal Center of the graymatter Contains CSFSpinal Cord (cont.)Ascending tracts – sensory Descending tracts – motorReflexes – predictable automatic responses Receptor Sensory NeuronsInterneurons Motor NeuronsEffectorsStimulusResponseBrainFour sectionsCerebrumDiencephalonBrain stemCerebellumCerebrumTwo hemispheresCorpus callosumSulciGyriLongtidtudinal fissure BrainBrain (cont.)Brain (cont.)Cerebral CortexGray matterFunctionsSensory informationBody movementMemoriesEmotions VentriclesInterconnected cavities within the brainCSFDiencephalonThalamusHypothalamusBrain (cont.)Brain StemMidbrain Pons Medulla oblongata Cerebellum Complex body movementsFine muscle movements BrainPrevious slideBrain (cont.)Apply Your KnowledgeMatch the following:___ Meninges A. Carry motor information from brain___ Ascending tracts B. Stores memories and creates emotions___ Descending tracts C. Grooves on the surface of the cerebrum___ Cerebral cortex D. Carry sensory information to the brain___ Hypothalamus E. Predictable, automatic response to stimuli___ Sulci F. Maintains homeostasis___ Cerebellum G. Coordinates skeletal muscle contractions___ Reflexes H. Protects the brain and spinal cordBFCGEDAHAnswer: SUPER!Peripheral Nervous SystemNerves that branch off the CNSCranial nerves Spinal nervesCranial NervesOlfactory nerves Optic nerves Oculomotor nerves Trochlear nerves Trigeminal nervesAbducens nervesDiagramCranial Nerves (cont.)Facial nerves Vestibulocochlear nerves GlossopharyngealnervesVagus nervesAccessory nervesHypoglossal nervesDiagramBackSpinal Nerves31 pairs of spinal nerves 8 pairs of cervical nerves 12 pairs of thoracic nerves 5 pairs of lumbar nerves 5 pairs of sacral nerves 1 pair of coccygeal nervesSpinal NervesSpinal Nerves (cont.)Dermatome Skin segment innervated by spinal nerveC1 is not associated with a dermatomeVentral root – axons of motor neuronsDorsal rootAxons of sensory neurons Dorsal root ganglion ~ cell bodies of sensory neuronsSpinal Nerves (cont.)Nerve plexusesCervical ~ skin and neckBrachial ~ armsLumbosacral ~ lower abdomen, external genitalia, buttocks, thighs, legs, and feetCoccygeal ~ anus and back of thighsSpinal NervesBackSomatic and Autonomic Nervous System Somatic Nervous SystemNerves that connect the CNS to skin and skeletal muscle“Voluntary” nervous system Controls skeletal musclesSomatic and Autonomic Nervous System (cont.) Autonomic Nervous SystemConnect the CNS to organs and other structures “Involuntary” nervous systemGangliaMotor neurons from brain and spinal cordMotor neurons in gangliaOrgans and blood vesselsSomatic and Autonomic Nervous System (cont.) Sympathetic division“Fight or flight” Prepares body for stressful or emergency situationsReleases norepinephrineControls constriction of blood vesselsSomatic and Autonomic Nervous System (cont.) Parasympathetic divisionPrepares body for rest and digestingControls most of the body’s organsReleases acetylcholineSympathetic and parasympathetic divisions are antagonisticApply Your KnowledgeWhat is the difference between the sympathetic and parasympathetic nervous systems?ANSWER: The sympathetic nervous system prepares the body for stress. It releases norepinephrine, causing an increase in heart and respiratory rate, slows down the GI system, and dilates pupils. The sympathetic system also controls constriction of blood vessels.The parasympathetic system prepares the body for resting and digesting. It releases acetylcholine, which slows heart and respiratory rates, constricts pupils, and stimulates the GI system. It has no effect on most blood vessels.Impressive!Neurologic TestingTypical neurologic examinationState of consciousness Reflex activity Speech patterns Motor patterns Diagnostic ProceduresLumbar punctureMagnetic resonance imaging (MRI)Positron emission tomography (PET) scan Cerebral angiographyComputerized tomography (CT) scan Electroencephalogram (EEG) X-rayCranial Nerve TestsOlfactory nerve (I) –have patient smell various substancesCranial nerves III, IV, and VI – have patient visually track movement of fingerCranial Nerve Tests (cont.)Cranial nerve V – have patient clench teeth, feel jaw musclesCranial nerve VII – check patient’s facial expressionCranial nerve XII – have patient extend and move tongue Reflex TestingTermsAreflexiaHyporeflexiaHyperreflexiaTestsBiceps reflexKnee reflexAbdominal reflexes Apply Your KnowledgeMatch the following: ___ State of consciousness A. Determines the health of peripheral nerves___ Reflex activity B. Loss of balance,  abnormal posture___ Speech patterns C. Stupor, delirium,  vegetative___ Motor patterns D. Loss of ability to form wordsADBCANSWER: ________ Common Diseases and Disorders of the Nervous SystemBrain and spinal cord injuriesCauses Motor vehicle accidentsSports and recreational accidentsViolenceChildren and teens at highest riskMost are preventableCommon Diseases and Disorders of the Nervous System (cont.)Disease/DisorderDescriptionAlzheimer’s diseaseProgressive, degenerative disease of the brainAmyotrophic lateral sclerosis (ALS)Degeneration of neurons in the spinal cord and brain; Lou Gehrig’s disease; fatalCommon Diseases and Disorders of the Nervous System (cont.)Disease/DisorderDescriptionBell’s palsyWeak or paralyzed facial musclesBrain tumors and cancersAbnormal growths Can be primary or secondary tumors; most common – gliomasCommon Diseases and Disorders of the Nervous System (cont.)Disease/DisorderDescriptionEpilepsy and seizuresOccurs as a result of bursts of electrical signals that disrupt normal brain functioningGuillain-Barré SyndromeBody’s immune system attacks the PNS; sudden and unexpected onsetCommon Diseases and Disorders of the Nervous System (cont.)Disease/DisorderDescriptionHeadachesTension MigrainesClusterEpisodic or chronicMost severe form of headacheSevere form of migraines; attacks occur in groupsCommon Diseases and Disorders of the Nervous System (cont.)Disease/DisorderDescriptionMeningitis Inflammation of meningesMultiple sclerosis (MS)Chronic disease of CNS; myelin is destroyedNeuralgiasDisorders causing nerve painCommon Diseases and Disorders of the Nervous System (cont.)Disease/DisorderDescriptionParkinson’s diseaseProgressive and degenerative motor system disorderSciaticaDamage to sciatic nerveStrokeBrain cells die because of an inadequate blood flow; “brain attack”Apply Your KnowledgeTrue or false: ___ Alzheimer’s disease is a progressive degenerative disease  of the brain.___ Epilepsy is due to degenerative neurons in the spinal cord and brain.___ Neuralgias are motor system disorders.___ Stroke occurs when brain cells die because of inadequate blood flow.FFTDue to a burst of electrical signals that disrupt brain function. They are group of disorders referred to as nerve pain.TANSWER:Bravo!In Summary30.1 The central nervous system is composed of the brain and spinal cord. The peripheral nervous system consists of the peripheral nerves located throughout the body. Three types of neurons carry out the functions of the nervous system: the afferent (sensory) nerves detect sensation or other stimuli from the body or environment and bring it to the CNS for interpretation, the efferent (motor) nerves produce movement or other functions at the direction of the CNS, and the interpretive interneurons act as “interpreters” between the afferent and efferent nerves. In Summary (cont.)30.2 All neurons are composed of a cell body, the shorter and more numerous dendrites that receive information for the cell body, and the longer axons that function to bring impulses from the cell body to the dendrite of the next neuron.In Summary (cont.)30.3 Nerve impulses send information either from the CNS to the PNS or vice versa. A synapse is the space between the axon of one neuron and the dendrite of the next. At the end of each axon is the synaptic knob, which contains vesicles that produce neurotransmitters. These are released by the synaptic bulb to allow impulse transmission to continue to the next neuron.In Summary (cont.)30.4 The brain consists of the cerebrum, diencephalon, brain stem, and cerebellum. Other structures include the blood-brain barrier and the meninges. The spinal cord consists of 31 spinal segments. The basic function of the spinal cord is to carry sensory information to the brain and motor information to the muscles and glands of the body. Cerebrospinal fluid (CSF) is located within the subarachnoid space and the central canal of the spinal cord. It cushions the brain and spinal cord.In Summary (cont.)30.5 The somatic nervous system connects the CNS to the skin and skeletal muscle (voluntary functions). The autonomic nervous system connects the CNS to the internal organs (involuntary functions). The autonomic nervous system is divided into the sympathetic system, which prepares the body for “fight or flight” (stressful) situations, and the parasympathetic system, which is the body’s everyday “resting” system for normal situations.In Summary (cont.)30.6 Tests commonly used to determine neurologic disorders include tests of the reflexes and cranial nerves, as well as diagnostic procedures such as lumbar puncture, MRI, PET, cerebral angiography, CT scan, EEG, and X-ray.30.7 Many types of diseases and disorders are related to the nervous system. The signs, symptoms, and treatments of these diseases are as varied as the diseases themselves. Many of the more common diseases are included in the pathophysiology section at the end of this  chapter. Activity of the nervous system improves the capacity for activity, just as exercising a muscle makes it stronger.”~ Dr. Ralph GerardEnd of Chapter 30