The Nervous The Nervous System: Spinal System: Spinal Cord and Spinal Cord and Spinal

NervesNerves

IntroductionIntroduction– Spinal cord Spinal cord

Truly the pathway between body and mindTruly the pathway between body and mind Conducts impulses to and from the brainConducts impulses to and from the brain Carries out spinal reflexesCarries out spinal reflexes

– Spinal nervesSpinal nerves 31 pairs31 pairs All are mixed nervesAll are mixed nerves

Gross Anatomy of the Gross Anatomy of the Spinal CordSpinal Cord

Coverings of the Spinal Coverings of the Spinal CordCord

– 3 layers called meninges3 layers called meninges– Dura materDura mater

Outer layerOuter layer Dense irregular connective tissueDense irregular connective tissue

– ArachnoidArachnoid Middle layerMiddle layer Encloses cerebrospinal fluidEncloses cerebrospinal fluid

– Pia materPia mater Adheres tightly to the surface of the spinal cordAdheres tightly to the surface of the spinal cord

Meninges of the Spinal Meninges of the Spinal CordCord

Sectional Anatomy of the Sectional Anatomy of the Spinal CordSpinal Cord

– Inner part consists of gray matterInner part consists of gray matter– Outer part consists of white matterOuter part consists of white matter

Sectional Anatomy of the Sectional Anatomy of the Spinal CordSpinal Cord

Example of Ascending Example of Ascending Nerve TractsNerve Tracts

Spinal NervesSpinal Nerves– – Connect to the spinal cord via rootsConnect to the spinal cord via roots– The roots unite into the spinal nerveThe roots unite into the spinal nerve

Dorsal rootDorsal root Ventral rootVentral root

– Spinal nerves exit through holes between the Spinal nerves exit through holes between the vertebraevertebrae

– Split into branchesSplit into branches Supply muscles and skin Supply muscles and skin

Spinal NervesSpinal Nerves

DermatomesDermatomes

Nerve PlexusesNerve Plexuses– Plexus = “braid”Plexus = “braid”– Nerves supplying the limbs form plexuses when Nerves supplying the limbs form plexuses when

they leave the spinal cordthey leave the spinal cord CervicalCervical

– Innervates neck and shoulderInnervates neck and shoulder BrachialBrachial

– Innervates shoulder and armInnervates shoulder and arm Lumbosacral Lumbosacral

– Innervates abdomen, hip, thigh, leg, genital regionInnervates abdomen, hip, thigh, leg, genital region– Sciatic nerveSciatic nerve

Nerve PlexusesNerve Plexuses

Cervical PlexusCervical Plexus

Brachial PlexusBrachial Plexus

Brachial PlexusBrachial Plexus

Lumbar PlexusLumbar Plexus

Sacral PlexusSacral Plexus

Spinal Reflexes Spinal Reflexes – Reflexes are automatic responses to stimuliReflexes are automatic responses to stimuli– Spinal reflexes result from the stimulation of a Spinal reflexes result from the stimulation of a

spinal reflex arc.spinal reflex arc.– Basic elements of a reflex arcBasic elements of a reflex arc

ReceptorReceptor Afferent pathway (sensory)Afferent pathway (sensory) Synapse in spinal cord (integrating center)Synapse in spinal cord (integrating center) Efferent pathway (motor)Efferent pathway (motor) Response (effector)Response (effector)

AA Reflex ArcReflex Arc

Stretch ReflexStretch Reflex