The Nervous System Part: 3

The Nervous SystemPart: 3Ms. HerreraSpinal CordExtends from the foramen magnum of the skull to the first or second lumbar vertebraComprised of 31 pairs of spinal nerves8 cervical12 thoracic5 lumbar 5 sacral1 coccygealExtends from the foramen magnum of the skull to the first or second lumbar vertebra

Spinal Cord AnatomyInternal gray matter is mostly cell bodiesDorsal (posterior) hornsAnterior (ventral) horns Gray matter surrounds the central canalCentral canal is filled with cerebrospinal fluidExterior white materconduction tractsDorsal Column: contains sensory (afferent) tracts Lateral & Ventral Column: Contains both ascending and descending (motor: efferent tracts)

Peripheral Nervous System (PNS)Comprised of nerves and ganglia (neuronal cell bodies) that are outside the CNSMixed nervesBoth sensory and motor fibersAll spinal nerves are mixedSensory (afferent) nervesCarry impulses toward the CNSFound in sensory structuresMotor (efferent) nervesCarry impulses away from the CNSArise in CSN and include nerves from Somatic and Autonomic division

Cranial Nerves There are a total of 12 that are identified by name and numberMostly serve the head and neckMost are mixed nerves, but three are sensory only

Peripheral Nervous System (PNS)

PNS: Spinal NervesThere is a pair of spinal nerves at the level of each vertebrae for a total of 31 pairsFormed by the combination of the ventral and dorsal roots of the spinal cordNamed for the region from which they arise

PNS: Spinal NervesSpinal nerves divide soon after leaving the spinal cordDorsal ramiserve the skin and muscles of the posterior trunkVentral ramiform a complex of networks (plexus) for the anterior

PNS: Spinal Nerves

PNS: Autonomic Nervous SystemA.K.A. involuntary nervous systemMotor subdivision of the PNSConsists only of motor nervesActions:Regulates activities of cardiac and smooth muscles and glandsTwo subdivisionsSympathetic divisionParasympathetic division

PNS: Differences Between Somatic and Autonomic Nervous SystemsSomaticAutonomicNervesone motor neuron

Effector organsskeletal muscle

Neurotransmittersalways use acetylcholine

Nervespreganglionic and postganglionic nerves

Effector organssmooth muscle, cardiac muscle, and glandsNeurotransmittersuse acetylcholine, epinephrine, or norepinephrine

Anatomy of the Autonomic Nervous System

PNS: Autonomic FunctioningSympatheticParasympatheticA.K.A. fight-or-flight responseResponse to unusual stimulusTakes over to increase activitiesRelease acetycholineRemember as the E division Exercise, excitement, emergency, and embarrassment

housekeeping activitiesConserves energyMaintains daily necessary body functionsRelease norepinephrineRemember as the D divisiondigestion, defecation, and diuresis