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  2. 2. THE BRAIN
  3. 3. 1.Constitutes about one-fifth of bodyweight2.Lies within the cranial cavity.3.Parts are:-cereberum-midbrain-pons-medulla oblongata-cerebellum
  4. 4. CEREBRUM1.Occupies the anterior and middle cranialfossae.2.Divided by a deep cleft,the longitudinalcerebral fissure into right and left cerebralhemisphere,each containing one of the lateralventricles.3.The hemispheres connected by a mass of whitematter called corpus callosum.4.Divided into lobes which take the names of thebones of the cranium:-frontal-parietal-temporal-occipital
  5. 5. INFERIOR OF THE CEREBRUM1.Surface of the cerebral cortex composedof gray matter.2.the lobes connected by masses of nervefibres or tract.Association(arcuate)-connect differentparts of a cerebral hemisphere byextending from one gyrus to another.Commissural tract-connect correspondingareas of the two cerebral hemisphere.Projection tract-connect the cerebral cortexwith grey matter of lower part of the brainand with the spinal cord.
  6. 6. Function of the cerebral cortex1.Mental activitiesex:memory,thinking,intelligence,moralsense,learning,reasoning2.Sensory perceptionEx:the perception of thepain,temperature,touch,hearing,taste,smell,sight3.Initiation and control of skeletal(voluntary)muscle contraction.
  7. 7. Functional areas of cerebralFunctional areas of cerebral cortexcortex1.Somatic sensory area – receivesimpulses from the body’s sensoryreceptors2.Primary motor area – sends impulses toskeletal muscles3.Association-intergration nad processingof complex mental function
  8. 8. Motor area of the of the cerebral cortexa)Primary motor area-control voluntarycontraction of specific muscle on the oppositeside of the body.e.g:finger maneuver(b)broca’s (motor speech) area-involve in thetranslation of thoughts into speech Sensory areas of the cerebral cortex (a)Somatosensory area-sensation of pain,temperature,pressure and touch,awareness of muscular movement and the position of joints are perceived. (b)Auditory area-nerve cells receive and interpet impulses transmitted from inner ear by the cochlear.
  9. 9. c)Olfactory area-impulses from thenose,transmitted via the olfactorynerves.(d)Taste area-impulses from sensoryreceptors in taste buds are receivedand perceived as taste(e)Visual area-optic nerve pass fromthe eye to this area,which receive andinterprets the impulses as visualimpression.
  10. 10. Association area(a)Premotor area-neurones coordinatemovement initiated by the primarymotor cortex.(b)Prefrontal area-intellectual functioncontrolled such as perception andcomprehension of passage of time.(c)wernicke’s (sensory speech)area-thespoken word is perceived andcomprehension and intelligence arebased.(d)parieto-occipitotemporal area-spatial awareness,interpreting writtenlanguage and ability to name object.
  11. 11. Others areas of the cerebrumBASAL GANGLIA1.Lying deep within the cerebral hemisphere.2.Involved in initiation and fine control of complexmovement and learned coordinated activitiesTHALAMUS1.Consist of two masses of nerve sense and fibressituated within cerebral hemisphere.2.Sensory input from the skin,viscera and specialsense organ is relayed to thalamus
  12. 12. HYPOTHALAMUS1.Situated below and in front of thethalamus,above the pituitary gland.2.Funtion are:-the autonomic nervous system-appetite and satiety-thirst and water balance-body temperature-emotional reaction-sexual behaviour-biological clocks
  13. 13. BRAIN STEMMIDBRAIN1.Situated around the cerebralaqueduct between thecerebrum above and the ponsbelow.2.Consist of nucleic and nervefibres(tract).3.Nucleic act as relay station forthe ascending and descendingnerve fibres.
  14. 14. PONS1.Situated in front of the cerebellum,below themidbrain and above the medulla oblongata.2.Nucleic within the pons that act as relay stationand associated with the cranial nerves.MEDULLA OBLONGATA1.Extend from pons above and is continous withspinal cord below.2.Has several special features:-decussation(crossing) of thepyramid.motor nervedescending from the motorarea in the cerebrum to the spinal cord in thepyramidaltracts.
  15. 15. -sensory decussation.sensory nerveascending to the cerebrum from the spinalcord cross from one side to other in themedulla.-the cardiovascularcentre(CVC).control the rate and forcecardiac contraction and blood pressure.-the respiratory centre.control therate depth of respiration-reflex centres.irritants present in thestomach or respiratory tract stimulate themedulla oblongata,activating the reflexcentres.
  16. 16. RETICULAR FORMATION1.Is a collection of neurones in the core ofthe brain stem,surrounded by neuralpathway.2.function:-coordination of skeletal muscle activityassociated with voluntary motor movementand the maintenance of balance.-coordination of activity controlled by theautonomic nervous system.-selective awareness that function throughthe reticular activating system(RAS).
  17. 17. CEREBELLUM1.Situated behind the pons andimmediately below the posterior portionof the cerebrum occupying the posteriorcranial fossae.2.function:-coordination of voluntary muscularmovement,posture and balance .-role in learning and languageprocessing.
  18. 18. SPINAL CORD
  19. 19. 1.elongated,almost cylindrical part of theCNS.2.Continuos above with the medullaoblongata and extend from the upperborder of the atlas to the lower borderof the 1st lumbar.3.Is the nervous tissue link between thebrain and the rest of the body.4.Incompletely divided into two equalparts,anteriorly by a short,shallowmedian fissure and posteriorly by a deepnarrow septum.
  20. 20. GREYMATTER1.Have 2 posterior,2 anterior and 2lateral columns.2.Is the transverse commisure andit is pierced by the central canal anextension from the fourthventricle.3.The nerve cell bodies may be:-sensory neurones,receiveimpulses from the periphery ofthe body-lower motor neurones,transmitimpulses to the skeletal muscle.-connector neurones,form spinalreflex arcs.
  21. 21. POSTERIOR COLUMNS OF GREYMATTER 1.Composed of cell bodies that stimulate by sensory impulses from the periphery. 2.Contribute to the formation of white matter of the cord and transmit the sensory impulses upwards to the brain. ANTERIOR COLUMNS OF GREY MATTER 1.Composedof cell bodies of the lower motor neurones that stimulate the upper motor neurnes.
  22. 22. WHITE MATTER1.Arranged in 3column:anterior,posterior andlateral.2.function:-ascending tract:sensory towardbrain-descending tract:motor from brain
  23. 23. 1.Consist of:-31 pairs of spinal nerves-12 pairs of cranial nerves-the autonomic nervous system2.Each nerve consist of numerous nervefibres collected into bundle and3.Has covering of protective connectivetissue:ENDONEURIUM-delicatetissue,surrounding each individual fibre.PERINEURIUM-smooth connectivetissue,surrounding each bundle of fibres.EPINEURIUM-fibrous tissue whichsurround and encloses a number ofbundles of nerve fibres
  24. 24. 1. 31 pairs of spinal nerves that leave the vertebral canal.-8 cervical-12 thoracic-5 lumbar-5 sacral-1 coccygeal2. Nerve is formed by the union:Mixed nerves – both sensory and motor fibersAfferent (sensory) nerves – carry impulses toward theCNSEfferent (motor) nerves – carry impulses away from theCNS3.The Anterior Nerve root -consists of motor nerve fibres.The Posterior nerve root: -consists of sensory nerve fibres
  25. 25. PLEXUSUS•Cervical•Brachial•Lumbar•Sacral
  26. 26. CERVICAL PLEXUS1.Cervical plexus (C1-C4) innervates themuscles and skin of the neck and shoulder.2.The superficial branches supply thestructures at the back and side of the headand skin of the front of neck.3.The deep branches supply muscle of theneck.e.g:the sternoleidomastoid
  27. 27. BRACHIAL PLEXUSMain nerves (be able tolabel):•Musculocutaneous C8,T1 –passesdownwards to the lateral aspect ofthe forearm.•Median C5,6,7,8,T1 – passes downthe midline of arm in closeassociation with the brachial artery.•Ulnar C7,8,T1 – passes behind themedial epicondyle of humerus.•Axillary C5,6– winds round thehumerus at the level of the surgicalneck.•Radial C5,6,7,8,T1– to posteriorpart of limb 31
  28. 28. LUMBAR PLEXUS1.Formed by anterior rami of the L1-L4.2.Lies within the psoas major muscle.3.Main branches:-iliohypogastric nerve L1-ilioinguinal nerve L1-genitofemoral L1,2-lateral cutaneous nerve of thigh L2,3(supplies the skin of the lateral aspect othigh)-femoral nerve L2,3,4 (passes behind theinguinal ligament to enter thigh)-obturator nerve L2,3,4 (supplies theadductor muscle of thigh and skin of themedial aspect of thigh)-lumbosacral trunk L4,5 (trunk dsecendsinto the pelvis)
  29. 29. SACRAL PLEXUS1. formed L4-S42.Supplies muscles and skin ofposterior thigh and almost all of theleg3.Main branch is the large sciaticnerve, which consists of: Tibial nerve – to most of hamstrings, calf and sole Common fibular nerve – to muscles of anterior and lateral leg and skin4.Other branches supply pelvic girdle(gluteus muscles) and perineum(pudental nerve)
  30. 30. COCCYGEAL PLEXUS 1.Formed by part of the 4th and 5th sacral and the coccygeal nerves. 2.Supply the skin around the coccyx and anal area
  31. 31. 1.Do not intermingle toform plexus.2.There are 12 pairs and 11are the intercoastal nervesand 12th pair comprise thesubcostal nerves.3.The 7th to 12th nervessupply the muscle and skinof the posterior andanterior abdominal wall
  32. 32. 1.There are 12 pairs of cranial nervesoriginating from nucleic in the inferior surfaceof the brain,some sensory,some motor andsome mixed.2.Names and numbers:I. olfactory:sensoryII. Optic:sensoryIII. Oculomotor:motorIV. Trochlear:motorV. Trigeminal:mixedVI. Abducent:motorVII.Facial:mixedVIII.Vestibulocochlear(auditory):sensoryIX. Glossopharyngeal:mixedX. Vagus:mixedXI. Accessory:motorXII.Hypoglossal:motor
  33. 33. CN Name Attached Foramen Function# toI Olfactory Forebrain Cribriform Sense of smell plateII Optic Forebrain Optic canal Sense of vision (sight) from retinaIII Oculomotor Midbrain Superior Motor to 4 of the 6 (brainste orbital muscles of eye m) fissure movement (up & in); eyelid; constriction of pupilIV Trochlear Midbrain Superior Motor to superior (brainste orbital oblique muscle of eye m) fissure (down & out)V Trigeminal Pons V1: superior All three divisions: facial V1 (brainste orbital sensation ophthalmic m) fissure V2 maxillary V2: foramen V3 rotundum V3 (mandibular mandibular V3: foramen division): chewing also ovale
  34. 34. VI Abducens Pons Superior orbital Motor to lateral rectus muscle (brainstem) fissure of eye (abducts outwards)VII Facial Pons Internal Facial expression (motor) (brainstem) auditory canal Taste anterior 2/3 tongue Salivary & lacrimal glands (saliva and tears)VIII Vestibulocochlear Pons Internal Equilibrium (vestibular) (brainstem) auditory Hearing (cochlear) canalIX Glossopharyngeal Medulla Jugular Taste & touch from posterior (brainstem) foramen 1/3 tongue (sour, bitter); pharynx (throat) muscles of swallowing; parotid gland (saliva); senses carotid BPX Vagus Medulla Jugular Senses aortic BP, slows heart (brainstem) foramen rate, stimulates digestive organs; larynx (vocal cords), taste, swallowingXI Accessory Medulla Jugular Sternocleidomastoid, trapezius, (brainstem) foramen swallowing; part joins VagusXII Hypoglossal Medulla Hypoglossal Innervation of tongue muscles (brainstem) canal
  35. 35. TH@NK YOU