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Chapter 9: Nervous System (Study Guide & Study Questions)CENTRAL NERVOUS SYSTEM (CNS)Brain & Spinal Cord (occupy the midline or central location of the body)Brain is protected in the cranial cavity of the skull.Spinal cord is surrounded in the spinal cavity by the vertebral column.Brain & spinal cord are also protected by 3 membranes (meninges).Divisions of the brain:I. Brainstem: A. Medulla Oblongata B. Pons C. MidbrainII. CerebellumIII. Diencephalon A. Hypothalamus B. Thalamus C. Pineal GlandIV. CerebrumBrainstem:Lowest part of the brainstem- medulla oblongataImmediately above the medulla is the pons and above that the midbrainMedulla oblongata- an enlarged, upper extension of the spinal cord. Lies inside the cranial cavity, above the foramen magnum (large hole in occipital bone)Pons bulges out a bit more than medulla, forming a bridge to the midbrainAll 3 parts function as a two-way conduction pathway.Sensory fibers conduct impulses up from the spinal cord to other parts of the brain, motor fibers conduct impulses down from the brain to spinal cordMany important reflex centers lie in brainstem, cardiac, respiratory, vasomotor centers (vital centers) – located in the medulla, impulses from these centers control heartbeat, respiration, blood vessel diameter CerebellumSecond largest part of brainLies under occipital lobe of the cerebrumFolded gray matter composes the thin outer layer and forms a large surface area of nervous connections (allow for huge amount of information processing)White matter tracts form most of the interior Plays an essential part in production of normal movementsLoss of normal cerebellar functioning, loose ability to make precise movementsProduce smooth coordinated movements, maintain equilibrium, sustain normal postures Diencephalon Located between the midbrain below and cerebrum aboveHypothalamus Located below the thalamusExerts major control over virtually all internal organsHelps control heartbeat, constriction & dilation of blood vessels, contractions of stomach & intestinesSome neurons make hormones that the posterior pituitary gland secretes into the blood, ADH (antidiuretic hormone) affects the volume of urine excreted, therefore hypothalamus plays an essential role in maintaining the body’s water balanceOther neurons function as endocrine (ductless) glandsIndirectly helps control the functioning of every cell in the bodyCrucial part of the mechanism for maintaining body temperature Involved in the regulation of water balance, sleep cycles, control of appetite & many emotions involved in pleasure, fear, anger, sexual arousal, & painThalamusJust above hypothalamus Dumb-bell shaped section of gray matterEach enlarged end of the dumbbell lies in a lateral wall of fluid-filled chamber (third ventricle)Relays sensory information: its neurons relay impulses to the cerebral cortex from the sense organs of the bodyAssociates sensations with emotions: seem to be associated with the arrival of sensory impulses in the thalamusRegulates level of consciousness: plays a part in arousal or alerting mechanism that keeps us awakeParticipates in motor reflexes: plays a role in mechanisms that produce complex reflex movements Pineal glandPosterior to the thalamus, protruding from the back of the diencephalonResembles a small pine nut or kernel of cornReceives sensory information about the strength of light seen by the eyes and adjusts its output of the hormone melatoninCerebrum Largest and uppermost part of the brainMany ridges (convolutions, gyri) & grooves (sulci, deepest sulci are called fissures)The longitudinal fissure divides the cerebrum into right and left halves (hemispheres) these halves are almost separate structures expect for an inferior central band (corpus callosum)Two deep sulci divide each cerebral hemisphere into four major lobes: frontal, parietal, temporal, occipital A thin layer of gray matter called the cerebral cortex, made up of neuron dendrites and cell bodies, forms the surface of the cerebrumWithin this matter are a few islands of gray matter known as the basal nuclei or basal ganglia, whose functioning is essential for producing automatic movements and postures.Functions: consciousness, thinking, memory, sensations, emotions, and willed movements, vision, hearing, normal speechSpinal CordIf you are average height your spinal cord is about 17 or 18 inches longLies in the spinal column in the spinal cavity & extends from the occipital bone down to the bottom of the first lumbar vertebraColumns of white matter form the outer portion of the spinal cord, and bundles of myelinated nerve fibers—the spinal tracts—make up the white columnsAscending tracts conduct impulses up the spinal cord to the brainDescending tracts conduct impulses down the spinal cord from the brainReflexes that result from conduction over arcs whose centers lie in the spinal cord – spinal cord reflexesWithdrawal and jerk are the two common kinds of spinal cord reflexes Withdrawal; pulling one’s hand away from a hot surfaceJerk; knee jerkSpinal cord injury that produces loss of sensation (anesthesia), loss of ability to make voluntary movements (paralysis)Coverings and fluid spacesNervous tissue is not a sturdy tissueTough, fluid cushioned set of membranes (meninges) (surrounds brain & spinal cord)3 layers of spinal meningesDura matter: the tough outer layer that lines the vertebral canalPia matter: innermost membrane covering the spinal cord itselfArachnoid matter: membrane between the dura and the pia matter Fluid fills the subarachnoid spaces between the pia matter and arachnoid in the brain and spinal cord----- Cerebrospinal fluid (CSF)CSF forms continually from fluid filtering out of the blood in a network of brain capillaries known as the choroid plexus and into the ventriclesCSF is one of the bodies circulating fluidsAccumulation of CSF in the ventricles; example = hydrocephalus (water on the brain”PERIPHERAL NERVOUS SYSTEMthe nerves connecting the brain and spinal cord to other parts of the body constitute the PNSincludes cranial nerves and spinal nerves (connect the brain and spinal cord to the peripheral structures such as the skin surface and the skin skeletal muscles)Autonomic nervous system (ANS) are part of the PNS (these connect the brain and spinal cord to various glands in the body and to the cardiac and smooth muscles in the thorax and abdomenCranial Nerves12 pairs of cranial nerves are attached to the undersurface of the brainNERVECONDUCT IMPULSESMAIN FUNCTIONSIOlfactoryNose to brainSense of smellIIOpticEye to brainVisionIIIOculomotorBrain to eye musclesEye movementsIVTrochlearBrain to external eye musclesEye movementsVTrigeminalSkin and mucous membrane of head & from teeth to brain; brain to chewing musclesSensations of face, scalp, & teeth; chewing movementsVIAbducensBrain to external eye musclesEye movementsVIIFacialTaste buds to brain; brain to face musclesSense of taste; contraction of muscles of facial expressionVIIIVestibulocochlearEar to brainHearing; sense of balanceIXGlossopharyngealThroat & taste buds to brain; brain to throat muscles & salivary glandsSensations of throat, taste, swallowing movements, secretion of salivaXVagusThroat, larynx, organs in thoracic & abdominal cavities to brain; brain to muscles of throat & to organs in thoracic and abdominal cavities Sensations of throat & larynx & of thoracic & abdominal organs; swallowing, voice production, slowing of heart beat, acceleration of peristalsis(gut movements)XIAccessoryBrain to certain shoulder and neck musclesShoulder movements; turning movements of headXIIhypoglossalBrain to muscles of tongue Tongue movementsOn Old Olympus’ Tiny Tops, A Friendly Viking Grew Vines And HopsSPINAL NERVES31 pairs of nerves are attached to the spinal cord (descending anatomical order listed below)8 pairs attached to cervical segments12 pairs attached to thoracic segments5 pairs attached to lumbar segments5 pairs attached to sacral segments1 pair attached to coccygeal segmentsSpinal nerves have NO special names, a letter and a number to identify eachEX: C1 indicates a pair of spinal nerves attached to the first segment of the cervical part of the spinal cord; T8- 8 segment of the thoracic part of the spinal cordPlexus- network of intersecting or “braided” branches Spinal nerves conduct impulses between the spinal cord and the parts of the body not supplied by cranial nerves ; function to make possible sensations & movementsSkin surface areas that are supplied by a single spinal nerve are called dermatomesAUTONOMIC NERVOUS SYSTEMANS consists of certain motor neurons that conduct impulses from the spinal cord or brainstem to: cardiac muscle tissue, smooth muscle tissue, glandular epithelial tissueANS includes parts of the nervous system that regulate involuntary functions (heartbeat, contractions of the stomach & intestines, secretions by glands) --- motor nerves that control the voluntary actions of skeletal muscles are somatic nervous systemANS has 2 divisions: sympathetic & parasympathetic Autonomic neurons are the motor neurons that make up the ANS- preganglionic autonomic neurons conduct from spinal cord or brainstem to an autonomic ganglion; postganglionic neurons conduct from autonomic ganglia to cardiac muscle, smooth muscle, glandular epithelial tissueAutonomic or visceral effectors- tissues to which autonomic neurons conduct impulses (that is cardiac, smooth, glandular)SYMPATHETIC DIVISON Also called thoracolumbar systemSympathetic preganglionic neurons have dendrites and cell bodies in the gray matter of the thoracic and upper lumbar segments of spinal cordAxons leave the spinal cord in the anterior roots of spinal nerves, extend to sympathetic or collateral ganglia & synapse with several postganglionic neurons whose axons extend to spinal or autonomic nerves to terminate in visceral effectorsA chain of sympathetic ganglia is in front of and at each side of the spinal columnFunctions: serves as an emergency or stress system, control when strong emotions (anger, fear, hate, anxiety) are triggered; group of changes induced by sympathetic control is called the fight-or-flight responsePARASYMPATHETIC DIVISONParasympathetic preganglionic neurons have dendrites and cell bodies in the gray matter of the brainstem and the sacral segments of the spinal cordParasympathetic preganglionic neurons terminate in parasympathetic ganglia locates in the head and the thoracic and abdominal cavities close to visceral effectorsEach parasympathetic preganglionic neuron synapses with postganglionic neurons to only one effector Function: dominates control of many visceral effectors under normal, everyday conditions; counterbalances sympathetic functionAutonomic functions:VISCERAL EFFECTORSSYMPATHETIC CONTROLPARASYMPATHETIC CONTROLHeart muscleAccelerates heartbeatSlows heartbeatSmooth muscleOf most blood vesselsConstricts blood vesselsOf blood vessels in skeletal musclesDilates blood vesselsOf digestive tractDecreases peristalsis; inhibits defecationIncreases peristalsisof anal sphincterStimulates—closes sphincterInhibits—opens sphincter for urinationOf the eyeIris Stimulates radial fibers—dilation of pupilStimulates circular fibers—contraction of pupilCiliary Inhibits-- accommodation for far vision (flattening of lens)Stimulates—accommodation for near vision (bluging of lens)Of hairs (arrector pili)Stimulates—“goose pimples”No parasympathetic fibersGlands Adrenal medullaIncreases epinephrine secretionSweat glands Increases sweat secretionDigestive glandsDecreases secretion of digestive juices Increases secretion of digestive juices AUTONOMIC NEUROTRANSMITTERSChemical compounds released from the axon terminals of autonomic neuronsCholinergic fibers – preganglionic axons of parasympathetic & sympathetic systems & parasympathetic postganglionic axons release acetylcholine (ACh)Adrenergic fibers --- axons of the sympathetic postganglionic neurons release norepinephrine (noradrenaline)AUTONOMIC NERVOUS SYSTEM AS A WHOLERegulates the body’s automatic functions in ways that maintain or quickly restore homeostasisMany visceral effectors are doubly innervated (that is, they receive fibers from parasympathetic and sympathetic divisions and are influenced in opposite ways by the two divisions)CELLS OF THE NERVOUS SYSTEMNeurons- nerve cellsGlia- support cells (glue)Neurons conduct impulses, glia support neuronsNEURONSCell body- main part Dendrites- one or more branching projectionsAxon- one elongated projection Dendrites are the processes or projections that carry impulses to the neuron cell bodies, and axons are the processes that carry impulses away from the neuron cell bodiesTYPES OF NEURONSSensory neurons (afferent neurons)- carry impulses to the spinal cord and brain from all parts of the body. Motor neurons (efferent neurons)- carry impulses away from the brain and spinal cord. Do not conduct impulses to all parts of the body- only to muscle & glandular epithelial tissueInterneurons (central or connecting neurons)- conduct impulses from sensory neurons to motor neurons. Also connect with each other to form complex, central networks of nerve fibersGLIA(neuroglia)- do NOT specialize in transmitting impulses, they are special types of supporting cellsGLIA=GLUEOne example: holds the functioning neurons together and protects themOne of the most common types of brain tumors “glioma” develops from glia Function: support cells, bringing the cells of nervous tissue together structurally & functionallyCENTRAL GLIAAstrocytes- star-shaped cells that anchor small blood vessels to neuronsMicroglia- small cells that move in inflamed brain tissue carrying on phagocytosisOligodendrocytes- form myelin sheaths on axons in the CNSPERIPHERAL GLIASchwann cells form myelin sheaths on axons of the PNSMyelin- white, fatty substance formed by glia, surrounding some axons as a sheathNodes of Ranvier- gaps in the myelin sheathNeurilemma- Outer layer of myelin sheath needed for repair of damaged axonsNERVES & TRACTSNerve- bundle of peripheral axonsNerve coverings- fibrous connective tissueEndoneurium- surrounds individual fibers within a nervePerineurium- surrounds a group (fascicle) of nerve fibersEpineurium- surrounds the entire nerveTract – bundle of central axonsWhite matter- tissue composed primarily of myelinated axons (nerves or tracts)Gray matter- tissue composed primarily of cell bodies and unmyelinated fibersNERVE SIGNALSReflex arcsNerve impulses are conducted from receptors to effectors over neuron pathways or reflex arcs; conduction by a reflex arc results in a reflex (involuntary contraction by a muscle or secretion by a gland)The simplest reflex arcs are two-neuron arcs--- consisting of sensory neurons synapsing in the spinal cord with motor neuronsThree-neuron arcs consist of sensory neurons synapsing in the spinal cord with motor neuronsNerve impulsesDefinition: self-propagating wave of electrical disturbance that travels along the surface of a neuron membrane (also called action potential)MechanismAt rest, the neuron’s membrane is slightly positive on the outside--- polarized---- from a slight excess of Na+ on the outsideA stimulus triggers the opening of Na+ channels in the plasma membrane of the neuron Inward movement of Na+ depolarizes the membrane by making the inside more positive than the outside at the stimulated point; this depolarization is a nerve impulse (action potential)Conduction of nerve impulsesContinuous conduction – the stimulated section of membrane immediately repolarizes, but by that time the depolarization has already triggered the next section of membrane to depolarize, thus propagating a wave of electrical disturbances (depolarizations) al the way down the membraneSaltatory conduction- in myelinated fibers, conduction can “jump” from gap to gap and thus greatly speed up the rate of conduction Synapse Definition: place where impulses are transmitted from one neuron to another (postsynaptic neuron)Synapses are made of 3 different structures: synaptic knob, synaptic cleft, plasma membraneNeurotransmitters bind to specific receptor molecules in the membrane of a postsynaptic neuron, opening ion channels & thereby stimulating impulse conductionTypes of neurotransmitters: acetylcholine (ACh), amines (norepinephrine, dopamine, serotonin), endorphins, enkephalins, nitric oxide (NO), and other compoundsChapter 9: Nervous System (Study Questions)_________________________ is the name of the nervous system division that includes the nerves that extend to the outlying parts of the body___________________________ is the name of the nervous system division that includes the brain and spinal cordA group of peripheral axons bundled together in an epineurium is called a ____________________________The two types of cells found in the nervous system are _____________________ & __________________________The knee jerk is a type of neural pathway called a ________________________________________________________ is a self-propagating wave of electrical disturbance that travels along the surface of a neuron’s plasma membraneThe exterior of a resting neuron has a slight ________________________ charge, wheras the interior has a slight _________________________ charge During a nerve impulse, _______________________ is the ion that rushes into the neuron The _______________________ is the place where impulses are passed from one neuron to anotherAcetylcholine and dopamine are examples of _________________________, which are chemicals used by neurons to communicate ______________________,___________________________ & ______________________ are the three membranes that make up the meninges.There are ____________ pairs of cranial nerves, and _______________ pairs of nerves that come from the spinal cord______________________ are skin surface areas supplied by a single spinal nerve______________________ is the part of the autonomic nervous system that regulates effectors during nonstress conditions_______________________ is the part of the autonomic nervous system that regulates the “fight-or-flight” responseThe preganglionic axons of the sympathetic nervous system release the neurotransmitter ______________________. The postganglionic axons release _______________________ The preganglionic axons of the parasympathetic nervous system release the neurotransmitter ______________________. The postganglionic axons release _______________________The autonomic nervous system consists of neurons that conduct impulses from the brain or spinal cord to ___________________ tissue, ______________________ tissue, and __________________________ tissueCells that make myelin for axons outside the CNSGlia cells that help form the blood-brain barrierA single projection that carries nerve impulses away from the cell bodyCells that make myelin for axons inside the CNSA white fatty substance that surrounds and insulates the axonCells that act as microbe-eating scavengers in the CNSA highly branched part of the neuron that carries impulses toward the cell bodyPart of the brainstem that is a conduction pathway between areas of the brain and body; influences respirationSensory relay station from various body areas to the cerebral cortex; also involved with emotions and alerting and arousal mechanismsCarries messages to and from the brain to the rest of the body; also mediates reflexes Part of the brainstem that contains cardiac, respiratory, and vasomotor centersSensory perception, willed movements, consciousness, and memory are mediated hereRegulates body temperature, water balance, sleep-wake cycles, appetite, and sexual arousalRegulates muscle coordination, maintenance of equilibrium, and posturePart of the brainstem that contains relays for visual and auditory impulses____ dendrite____ axon____ myelin____ schwann cells____ astrocyte____ microglia____ oligodendrocyte____ medulla oblongata____ pons____ midbrain____ hypothalamus____ thalamus____ cerebellum____ cerebrum____ spinal cord MatchSubdivision of peripheral nervous systemEarBrain and spinal cordNerves that extend to the outlying parts of the body___ sense organ___ central nervous system___ peripheral nervous system___ autonomic nervous systemMatch Gaps between adjacent schwann cellsBranching projection of neuronAlso known as efferentForms myelin outside of the central nervous systemTough sheath that covers the whole nerveGroups of wrapped axon___ dendrite___ schwann cell___ motor neuron___ nodes of ranvier___ fascicles___ epineuriumMatchNeuronsNeuroglia___ axon___ special type of supporting cells___ Astrocytes___ sensory___ conduct impulses___ forms the myelin sheath around central nerve fibers___ phagocytosis___ efferent___ multiple sclerosis___ neurilemmaNerve impulses (do or do not) continually race along every nerve cell’s surfaceWhen a stimulus acts on a neuron, it (increases or decreases) the permeability of the stimulated point of its membrane to sodium ionsAn inward movement of positive ions leaves (a lack or an excess) of negative ions outsideThe plasma membrane of the (presynaptic or postsynaptic) neuron makes up a portion of the synapseA synaptic knob is a tiny bulge at the end of the (presynaptic or postsynaptic) neuron’s axonAcetylcholine is an example of a (neurotransmitter or protein molecule receptor)Neurotransitters are chemicals that allow neurons to (communicate or reproduce) with one anotherNeurotransmitters are distributed (randomly or specifically) into groups of neuronsCatecholamines may play a role in (sleep or reproduction)Endorphins and enkephalins are neurotransmitters that inhibit conduction of (fear or pain) impulsesWhich of the following is part of the brainstem?ThalamusCerebellumCerebrumHypothalamusMedullaWhich of the following is NOT a function of the brainstem?Conduction of sensory impulses from the spinal cord to the higher centers of the brainConduction of motor impulses from the cerebrum to the spinal cordControl of heartbeat, respiration, and blood vessel diameterContainment of centers for speech and memoryWhich one of the following is NOT part of the diencephalon?CerebrumThalamusHypothalamusAll of the above are correct ADH is produced by the:Pituitary glandMedullaMammillary bodiesThird ventricle HypothalamusWhich one of the following is NOT true about the hypothalamus?It helps control the rate of heartbeatIt helps control the constriction and dilation of blood vesselsIt helps control the contraction of the stomach and intestinesIt produces releasing hormones that control the release of certain anterior pituitary hormonesAll of the above are trueWhich one of the following parts of the brain helps in the association of sensations with emotions and also aids in the arousal or alerting mechanism?Pons HypothalamusCerebellumThalamusNone of the aboveWhich of the following is NOT true of the cerebrum?Its lobes correspond to the bones that lie over themIts grooves are called gyriMost of its gray matter lies on the surface of the cerebrumIts outer region is called the cerebral cortexIts two hemispheres are connected by a structure called the corpus callosumWhich one of the following is NOT a function of the cerebrum?Willed movementsConsciousnessMemoryConscious awareness of sensationsAll of the above are functions of the cerebrumThe area of the cerebrum responsible for the preception of sounds lies in the _________ lobeFrontal Temporal OccipitalParietalVisual perception is located in the ________ lobeFrontal Temporal ParietalOccipitalNone of the aboveWhich one of the following is not a function of the cerebellum?Maintains equilibriumHelps with production of smooth, coordinated movementsHelps maintain normal postureAssociates sensations with emotionsWithin the interior of the cerebrum are a few islands of gray matter known as FissuresBasal gangliaGyriMyelinA cerebrovascular accident is commonly referred to asA strokeParkinson’s diseaseA tumorMultiple sclerosisParkinson’s disease is a disease of the:MyelinAxonsNeurogliaCerebral basal nucleiThe largest section of the brain is the:CerebellumPonsCerebrum MidbrainMatch Cranial nervesSpinal nerves ___ 12 pairs___ dermatome___ vagus___ shingles ___ 31 pairs___ optic___ C1___ plexusDendrites and cell bodies of sympathetic preganglionic neurons are located in theBrainstem and sacral portion of the spinal cordSympathetic gangliaGray matter of the thoracic and upper lumbar segments of the spinal cordGanglia close to effectors Which of the following statements is NOT correct:Sympathetic preganglionic neurons have their cell bodies located in the lateral gray column of certain parts of the spinal cordSympathetic preganglionic axons pass along the dorsal root of certain spinal nervesThere are synapses within sympathetic gangliaSympathetic responses are usually widespread, involving many organsAnother name for parasympathetic nervous system isThoracolumbarCraniosacral VisceralANSCholinergic Which of the following statements is NOT correct?Sympathetic postganglionic neurons have their dendrites and cell bodies in sympathetic ganglia or collateral ganglia Sympathetic ganglions are located in front of and at each side of the spinal columnSeparate autonomic nerves distribute many sympathetic postganglionic axons to various internal organsSeparate autonomic nerves distribute many sympathetic postganglionic axons to various internal organsVery few sympathetic preganglionic axons synapse with postganglionic neuronsSympathetic stimulation usually results inResponse by numerous organsResponse by only one organIncreased peristalsisConstriction of pupilsParasympathetic stimulation frequently results in Response by only one organResponses by numerous organThe “flight-or-flight” responseIncreased heartbeatMatch Sympathetic control Parasympathetic control___ constricts pupils___ produces “goose pimples”___ increases sweat secretion___ increases secretion of digestive juices___ constricts blood vessels___ slows heartbeat___ relaxes bladder___ increases epinephrine secretion___ increases peristalsis___ stimulates lens of near visionWhich of the following conduct impulses toward the cell body?AxonsAstrocytesMicrogliaDendrites The outer cell membrane of a Schwann cell is called the:GliomaNeurilemmaCell bodyDendrite The myelin sheath in the brain and spinal cord is produced by theOligodendrocytesSchwann cellsMicrogliaBlood-brain barrierThe simplest kind of reflex arc is a(n):One-nuron arcTwo-neuron arcThree-neuron arcAction potential A ganglion is a group of nerve cell bodies located in the:PNSCNSBrain and spinal cordAll of the above Each synaptic knob vesicle contains a very small quantity of a chemical compound called a(n):SynapseADHReleasing hormoneNeurotransmitterWhich of the following is located in the brainstem?Medulla oblongataPonsMidbrainAll of the aboveWhich of the following is a function of the hypothalamus?Muscle coordinationWilled movementsRegulation of body temperatureRelay for visual impulsesWhich of the following is NOT true regarding the meninges?The tough outer layer is the dura materThe arachnoid mater is the membrane between the dura mater and the pia materThe pia mater resembles a “cobweb”, and the name comes from the Greek word for spiderAll of the above statements are true ................
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