structural organization of nervous system new

STRUCTURAL ORGANIZATION OF NERVOUS SYSTEM

INTRODUCTION

NERVOUS SYSTEM

• NERVOUS SYSTEM AND ENDOCRINE SYSTEM CONTROL THE FUNCTIONS OF THE BODY

• NERVOUS SYSTEM ENABLES THE BODY TO REACT TO CONTINUOUS CHANGES IN ITS INTERNAL AND EXTERNAL ENVIRONMENT

• CONTROLS AND INTEGRATES THE VARIOUS ACTIVITIES OF THE BODY LIKE CIRCULATION AND RESPIRATION

NERVOUS SYSTEM

• DIVISION OF NERVOUS SYSTEM• NERVOUS SYSTEM IS DIVIDED• STRUCTURALLY INTO---- CNS• ---- PNS• FUNCTIONALLY INTO---- SOMATIC• ---- AUTONOMIC

NERVOUS SYSTEM

• CELLS OF NERVOUS SYSTEM• CONSISTS OF TWO MAIN TYPES OF CELLS• 1 NEURONS• 2 NEUROGLIA• NEURONES• STRUCTURAL AND FUNCTIONAL UNITS OF

NERVOUS SYSTEM• COMPOSED OF A CELL BODY &PROCESSES

NERVOUS SYSTEM

• NEURONES [CONTD ]• PROCESSES ARE—DENDRITES &• ---AXONS• MYELIN CONSISTS OF LAYERS OF LIPIDS AND

PROTEINS• FORMS A SHEATH AROUND SOME AXONS

WHICH INCREASES THE VELOCITY OF IMPULSE CONDUCTION

NERVOUS SYSTEM

• NEUROGLIA• NONEXCITABLE• FORM A MAJOR COMPONENT OF NERVOUS

TISSUE• SUPPORT, INSULATE AND NOURISH THE

NEURONS

NERVOUS SYSTEM

• NEUROGLIA [ CONTD ]• IN THE CNS INCLUDE---• OLIGODENDROCYTES• ASTROCYTES• EPENDYMAL CELLS• MICROGLIA• IN THE PNS INCLUDE---• SATELLITE CELLS• SCHWANN CELLS

NERVOUS SYSTEM

• CNS• CONSISTS OF BRAIN AND SPINAL CORD• MAIN FUNCTIONS• 1 INTEGRATE AND COORDINATE INCOMING

AND OUTGOING NEURAL SIGNALS• 2 CARRY OUT HIGHER MENTAL FUNCTIONS

SUCH AS THINKING AND LEARNING

NERVOUS SYSTEM

• CNS [ CONTD ]• NUCLEUS---COLLECTION OF NERVE CELL

BODIES IN THE CNS• TRACT---ABUNDLE OF NERVE FIBRES[AXONS]

CONNECTING NEIGHBOURING AND DISTANT NUCLEI OF THE CNS

• BRAIN AND SPINAL CORD COMPOSED OF GREY MATER & WHITE MATER

NERVOUS SYSTEM

• CNS [ CONTD ]• GREY MATER FORMED BY NERVE CELL BODIES• WHITE MATER FORMED BY

INTERCONNECTING FIBRE TRACT SYSTEM• MENINGES• MEMBRANOUS LAYERS THAT COVER THE

BRAIN AND SPINAL CORD

NERVOUS SYSTEM

• MENINGES [CONTD ]• THREE LAYERS---• PIA MATER—INNERMOST• ARACHNOID MATER –MIDDLE• DURA MATER—OUTERMOST• CSF PRESENT B/W ARACHNOID AND PIA

MATER

NERVOUS SYSTEM

• PNS• CONSISTS OF NERVE FIBRES AND NERVE CELL

BODIES OUTSIDE THE CNS THAT CONDUCT IMPULSES TO OR AWAY FROM THE CNS

• PNS MADE UP OF NERVES THAT CONNECT THE CNS WITH PERIPHERAL STRUCTURES

• PERIPHERAL NERVE IS A BUNDLE OF NERVE FIBRES[AXONS] IN THE PNS

• GANGLION IS A COLLECTION OF NERVE CELL BODIES OUTSIDE THE CNS

NERVOUS SYSTEM

• PNS• CONSISTS OF NERVE FIBRES AND NERVE CELL

BODIES OUTSIDE THE CNS THAT CONDUCT IMPULSES TO OR AWAY FROM THE CNS

• PNS MADE UP OF NERVES THAT CONNECT THE CNS WITH PERIPHERAL STRUCTURES

• PERIPHERAL NERVE IS A BUNDLE OF NERVE FIBRES[AXONS] IN THE PNS

• GANGLION IS A COLLECTION OF NERVE CELL BODIES OUTSIDE THE CNS

NERVOUS SYSTEM

• PNS[CONTD]• PERIPHERAL NERVES• CRANIAL--- 12 PAIRS 12th PAIR ARISES MOSTLY FROM

THE SUPERIOR PART OF SPINAL CORD• SPINAL--- 31 PAIRS• C—8• T---12• L ---5• S ---5• CO-1

MAJOR DIVISIONS OF CNS

• SPINAL CORD• PRESENT WITHIN THE VERTEBRAL CANAL• SURROUNDED BY THREE LAYERS OF MENINGES• ROUGHLY CYLINDRICAL• BEGINS AT FORAMEN MAGNUM• INFERIORLY TAPERS OFF INTO CONUS

MEDULLARIS• TERMINATES AT THE LOWER BORDER OF L1 IN THE

ADULT

MAJOR DIVISIONS OF CNS

• SPINAL CORD [CONTD ]• FILUM TERMINALE IS A PROLONGATION OF PIA MATER –

EXTENDS FROM THE APEX OF CONUS MEDULLARIS AND IS ATTACHED TO THE BACK OF COCCYX

• 31 PAIRS OF SPINAL NERVES ATTACHED TO THE SP CORD• EACH SPINAL NERVE ATTACHED BY TWO ROOTS---• ANTERIOR OR MOTOR ROOT AND• POSTRIOR OR SENSORY ROOT• POSTERIOR ROOT GANGLION PRESENT ON POSTERIOR ROOT• CELLS IN THE GANGLION GIVE RISE TO CENTRAL AND

PERIPHERAL PROCESSES

MAJOR DIVISIONS OF CNS

• STRUCTURE OF SPINAL CORD• COMPOSED OF-- INNER CORE OF GREY MATER

SURROUNDED BY—OUTER CORE OF WHITE MATER

• GREY MATER IN CROSS SECTION IS H SHAPED WITH ANTERIOR AND POSTERIOR HORNS UNITED BY A THINLAYER OF GREY COMMISSURE CONTAINING THE CENTRAL CANAL

MAJOR DIVISIONS OF CNS

• STRUCTURE OF SP CORD [CONTD ]• IN THE THORACIC SEGMENT LATERAL HORNS

ARE ALSO PRESENT

• WHITE MATER DIVIDED INTO---• ANTERIOR WHITE COLUMN• LATERAL WHITE COLUMN• POSTERIOR WHITE COLUMN

MAJOR DIVISIONS OF CNS

• BRAIN• PRESENT IN THE CRANIAL CAVITY• SURROUNDED BY THREE LAYERS OF

MENINGES• DIVIDED INTO THREE MAJOR DIVISIONS---• HINDBRAIN• MIDBRAIN• FOREBRAIN

HIND BRAIN

• DIVIDED INTO---• MEDULLA OBLONGATA• PONS• CEREBELLUM

MEDULLA OBLONGATA

• CONICAL IN SHAPE• CONNECTS THE PONS TO THE SPINAL CORD• CONTAINS A NUMBER OF NUCLEI• SERVES AS A PASSAGE FOR ASCENDING AND

DESCENDING TRACTS

PONS

• PRESENT ON THE ANTERIOR SURFACE OF THE CEREBELLUM

• CONNECTS THE MIDBRAIN TO THE MEDULLA• HAS LARGE NUMBER OF TRANSVERSE FIBRES

CONNECTING THE TWO CEREBELLAR HEMISPHERES

• CONTAINS MANY NUCLEI AND ASCENDING AND DESCENDING NERVE FIBRES

CEREBELLUM

• PRESENT IN THE POSTERIOR CRANIAL FOSSA• THE TWO HEMISPHERES CONNECTED BY

VERMIS• CONNECTED TO THE MIDBRAIN BY—SUPERIOR

CEREBELLAR PEDUNCLES• CONNECTED TO THE PONS BY---MIDDLE

CEREBELLAR PEDUNCLE• CONNECTED TO THE MEDULLA BY---INFERIOR

CEREBELLAR PEDUNCLE

CEREBELLUM

• SURFACE LAYER CALLED THE CORTEX• CORTEX COMPOSED OF GREY MATER• CORTEX THROWN INTO FOLDS/FOLIA SEPARATED

BY TRANSVERSE FISSURES• INTRACEREBELLAR NUCLEI ARE FOUR ON EACH

SIDE ---DENTATE• ---EMBOLIFORM• ---GLOBOSE• ---FASTIGIAL

HINDBRAIN

• CAVITY OF HINDBRAIN IS 4th VENTRICLE• 4th VENTRICLE CONNECTED TO 3rd VENTRICLE

BY THE CEREBRAL AQUEDUCT• CONTINUOUS INFERIORLY WITH THE CENTRAL

CANAL OF SP CORD• COMMUNICATES WITH SUBARACHNOID

SPACE THROUGH THREE OPENINGS IN THE ROOF

MIDBRAIN

• NARROW PART THAT CONNECTS THE FOREBRAIN TO THE HINDBRAIN

• CAVITY IS THE CEREBRAL AQUEDUCT• CONTAINS MANY NUCLEI AND ASCENDING

AND DESENDING FIBRES

DIENCEPHALON

• HIDDEN FROM THE SURFACE OF THE BRAIN• CONSISTS OF ---• DORSAL THALAMUS• VENTRAL HYPOTHALAMUS• ITS CAVITY IS 3rd VENTRICLE• THALAMUS IS PRESENT ON EITHER SIDE OF

THE 3rd VENTRICLE

CEREBRUM

• LARGEST PART OF THE BRAIN• CONSISTS OF TWO HEMISPHERES CONNECTED

BY COROUS CALLOSUM• HEMISPHERES SEPARATED BY LONGITUDINAL

FISSURE• CORTEX IS THE SURFACE LAYER• CORTEX COMPOSED OF GREY MATER• CORTEX THROWN INTO FOLDS –THE SULCI

CEREBRUM

• GYRI SEPARATED BY FISSURES OR SULCI• LARGE SULCI ARE USED TO SUBDIVIDE EACH

HEMISPHERES INTO LOBES---• FRONTAL LOBE• PARIETAL LOBE• OCCIPITAL LOBE• TEMPORAL LOBE

CEREBRUM

• CENTRAL CORE OF WHITE MATER• CONTAINS LARGE MASSES O0F GREY MATER• CORONA RADIATA—FAN SHAPED COLLECTION OF

NERVE FIBRES• CORONA RADIATA CONVERGES ON THE BASAL NUCLEI

AND PASSES B/W THEM AS INTERNAL CAPSULE• CAUDATE NUCLEUS IS MEDIAL TO INTERNAL CAPSULE• LENTIFORM NUCLEUS IS LATERAL TO INTERNAL

CAPSULE

CEREBRUM

• CAVITY OF CEREBRAL HEMISPHERES IS LATERAL VENTRICLE

• LATERAL VENTRICLE COMMUNICATES WITH THE 3rd VENTRICLE THROUGH INTERVENTRICULAR FORAMEN

MAJOR DIVISIONS OF PNS

• 12 PAIRS OF CRANIAL NERVES---LEAVE THE BRAIN AND PASS THROUGH THE FORAMINA IN THE SKULL

• 31 PAIRS OF SPINAL NERVES---LEAVE THE SPINAL CORD AND PASS THROUGH INTERVERTEBRAL FORAMINA

SPINAL NERVES

• EACH SPINAL NERVE IS CONNECTED TO THE SPINAL CORD BY TWO ROOTS---

• ANTERIOR ROOT—CONSISTS OF EFFERENT/MOTOR NERVE FIBRES CARRYING IMPULSES AWAY FROM THE CNS—CELL BODIES IN THE ANTERIOR GREY HORN OF SP CORD

• POSTERIOR ROOT---CONSISTS OF AFFERENT/SENSORY NERVE FIBRES CARRYING IMPULSES TO THE CNS-- CELL BODIES IN THE POST ROOT GANGLION

SPINAL NERVES

• EACH SPINAL NERVE IS AMIXED NERVE CONTAINING BOTH MOTOR AND SENSORY FIBRES

• IN THE UPPER CERVICAL REGION THE ROOTS ARE SHORT AND ALMOST HORIZONTAL

• LENGTH OF THE ROOTS INCREASES FROM ABOVE DOWNWARDS

• THE ROOTS OF LUMBER AND SACRAL NERVES FORM A VERTICAL LEASH CALLED THE CAUDA EQUINA

SPINAL NERVE• EACH SPINAL NERVE IS A SHORT TRUNK • AFTER EMERGING FROM THE INTERVERTEBRAL FORAMEN IT

DIVIDES INTO –• ANTERIOR RAMUS AND SUPPLIES THE MUSCLES AND SKIN OVER

THE ANTEROLATERAL BODY WALL • ANTERIOR RAMI JOIN ONE ANOTHER AT THE ROOT OF THE LIMBS

TO FORM NERVE PLEXUSES• CERVICAL AND BRACHIAL PLEXUSES AT THE ROOT OF UPPER

LIMB• LUMBER AND SACRAL PLEXUSES AT THE ROOT OF LOWER LIMB • POSTERIOR RAMUS –PASSES TO THE BACK AND SUPPLIES

THEMUSCLES AND SKIN OF THE BACK

SPINAL GANGLIA

• THEY ARE SENSORY GANGLIA• SITUATED ON THE POSTERIOR ROOT OF EACH

SPINAL NERVE• FUSIFORM SWELLINGS