Brain stem dr.gosai

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Brain stem: Medulla Oblongata, Pons , Midbrain: External and Internal Features and Applied Aspect

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Brain stem dr.gosai

  1. 1. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai Brain stem Introduction:  It is part of central nervous system connecting spinal cord with the forebrain. Location:  Posterior cranial fossa on basilar part of occipital bone. Parts: (From Above downwards) (****Viva)  Midbrain  Pons  Medulla oblongata Anterior surface of Brainstem Posterior surface of Brainstem Midbrain Pons Medulla oblongata Pons Midbrain Medulla oblongata
  2. 2. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai Midbrain:  Upper most part of brain stem.  It connects brainstem to diencephalon and cerebrum. External Features: (Midbrain) (***viva) Anterior surface of Brainstem Posterior surface of Brainstem Features on Anterior surface:  Cerebral peduncles (Crus cerebri): Diverging peduncles are bundle of fibers seen on anterior surface. Features on Posterior surface:  Colliculi: (All four colliculi together also known as Corpora Quadrigemina or tectum of midbrain) 1. Two superior colliculi: (Concerned with Visuospinal reflex) 2. Two inferior colliculi: (Relay station of Auditory pathway) Cerebral peduncle Occulomotor nerve Trochlear nerve Inferior colliculus Superior colliculus
  3. 3. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai Nerves emerging from Midbrain: (***Viva)  Occulomotor nerve (III cranial nerve): emerging from medial aspect of cerebral peduncles on anterior surface supplies all muscles of eyeball except Superior oblique and Lateral rectus.  Trochlear nerve (IV cranial nerve): emerging from posterior surface of midbrain below inferior colliculus. (ONLY CRANIAL NERVE EMERGING FROM POSTERIOR SURFACE) Internal Features: Internal features studied by two sections of midbrain: 1. Transverse Section (T.S.) at level of superior colliculus 2. Transverse Section (T.S.) at level of inferior colliculus Transverse Section (T.S.) at level of superior colliculus:
  4. 4. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai  Gray matter seen in the section: (Nuclei seen at this level) (***viva) 1. Occulomotor nucleus: in the periaqueductal region supplies all muscles of eyeball except superior oblique and lateral rectus. It is also contain fibers of Edinger Westphal nucleus (Parasympathetic nucleus) for light reflex and accommodation reflex. 2. Red nucleus: red colous nucleus in tegmentum of midbrain concerned with motor activity. 3. Substantia Nigra: Purple colour nucleus between crus cerebri and tegmentum. They are dopaminergic neurons and damage to this neurons leads to Parkinson’s disease. 4. Nucleus of superior colliculs: Center for Visuospinal reflex (Movement of eyeball, head and neck and trunk while following a moving object for example looking at the flying objects like plane).  White matter seen in the section: (***viva) 1. Crus cerebri: containing corticopontine fibers from cortex to pontine nuclei and corticonuclear and corticospinal tracts. 2. Spinal lemniscus: Bundle of fibers containing spinothalamic tracts to thalamus. 3. Trigeminal lemniscus: Bundle of fibers containing sensory fibers from trigeminal nerve to thalamus. 4. Medial lemniscus: Bundle of fibers containing posterior column fibers from spinal cord to thalamus.
  5. 5. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai Transverse Section (T.S.) at level of inferior colliculus:  Gray matter seen in the section: (Nuclei seen at this level) (***viva) 1. Troclear nucleus: in the periaqueductal region supplies superior oblique muscle of eye 2. Substantia Nigra: Purple colour nucleus between crus cerebri and tegmentum. They are dopaminergic neurons and damage to this neurons leads to Parkinson’s disease. 3. Nucleus of inferior colliculs: Relay station of Auditory pathway of hearing.  White matter seen in the section: (***viva) 1. Crus cerebri: containing corticopontine fibers from cortex to pontine nuclei and corticonuclear and corticospinal tracts. 2. Superior cerebellar peduncle: Fibers from cerebellum cross in midbrain at this level.
  6. 6. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai 3. Spinal lemniscus, Trigeminal lemniscus and Medial lemniscus same as section at level of superior colliculus). 4. Lateral lemniscus: Bundle of fibers containing auditory pathway to inferior colliculus for relay. Applied anatomy of Midbrain: (***viva)  Trauma to midbrain: due to sharpe edge of tentorium cerebelli.  Ipsilateral paralysis of muscles of eye  Dilated pupil and loss of accommodation reflex and light reflex  Blockage of cerebral aqueduct:  It leads to Hydrocephalus.  Weber’s Syndrome:  Occlusion of Posterior cerebral artery  Involve Occulomotor nerve and crus cerebri.  Ipsilateral ophthalmopegia  Contralateral paralysis of lower part of face, tongue, arm and leg  Eyeball deviated laterally (Paralysis of medial rectus)  Drooping of eyelid (ptosis)  Pupil is dilated and fixedto light and accomodation reflex
  7. 7. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai  Benedict’s Syndrome:   Occlusion of Posterior cerebral artery  Similar to Weber’s syndrome with following differences:  Involve Medial lemniscus and Red nucleus  Contralateral hemianesthesia  Involuntary movements of limbs on opposite side.
  8. 8. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai Pons:  Middle and widest part of brain stem.  It is between medulla oblongata and midbrain. Anterior surface of Brainstem Posterior surface of Brainstem External Features: (***viva) Features on Anterior surface:  Basilar sulcus: Midline sulcus which is occupied by Basilar Artery.  Transverse running fibres on the surface: Pontocerebellar fibres which continues as Mddle cerebellar peduncle  Trigeminal nerve emerge at lateral part of pons Basilar Sulcus Trigeminal nerve Facial colliculus
  9. 9. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai Features on Posterior surface: (***viva)  Median sulcus in the midline  Facial colliculus: Paramedian elevation raised by underlying abducent nucleus covered by winding fibres of facial nerve Nerves emerging from Pons: (***viva)  Trigeminal nerve (V cranial nerve): emerging from lateral part. It demarcates between pons and middle cerebellar peduncle. Internal Features: Internal features studied by two sections of Pons:  It is divided into two parts by transversely running fibers known as Trapezoid body:  Basilar part: Anterior part  Tegmentum: Posterior part  Basilar part is same at both level of sections:  Basilar part contains: Pontocerebellar tract (transversely running) & Corticospinal tract (Vertically running) and dispersed Pontine nuclei 1. Transverse Section (T.S.) at level of Trigeminal nuclei 2. Transverse Section (T.S.) at level of Facial colliculus
  10. 10. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai Transverse Section (T.S.) at level of Trigeminal nuclei:  Gray matter seen in the section: (Nuclei seen at this level) (**viva) 1. Motor nucleus of trigeminal nerve: supply muscles of mastication. 2. Principal sensory nucleus of trigeminal nerve: Lateral to motor nucleus (Touch and Pressure sensations from Face) (**viva)  White matter seen in the section: 1. Trapezoid body (Fibers derived from cochlear nuclei and run transversely) 2. Medial lemniscus: Continuation of posterior column fibers 3. Spinal lemniscus: Spinothalamic tracts 4. Lateral Lemniscus: Continuation of auditory pathway
  11. 11. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai Transverse Section (T.S.) at level of Facial colliculus:  Gray matter seen in the section: (Nuclei seen at this level) (****Viva) 1. Facial nucleus: Supply muscles of facial expression. Facial nerve from facial nucleus winds around the abducent nucleus.(Neurobiotaxis) 2. Abducent nucleus: supply Lateral rectus muscle of eye. 3. Vestibular and cochlear nuclei  White matter seen in the section: 1. Trapezoid body 2. Medial longitudinal fasciculus 3. Spinal lemniscus, Medial Lemniscus and Lateral Lemniscus: (Same as above section )
  12. 12. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai Applied Anatomy of Pons Tumors of pons:  Occuring in childhood  Weakness of facial muscles, Lateral rectus paralysis (Medial squint of eye) and contralateral hemiparesis is characteristic of involvement of Pons.  Nystagmus  Impairment of hearing  Weakness of jaw muscles Pontine hemorrhage: (****viva)  Hemorrhage from basilar artery  “Pinpoint” pupil  Facial paralysis same side  Paralysis of muscles of opposite side
  13. 13. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai Medulla Oblongata:  Lower part of brain stem  Continues as Spinal cord at foramen magnum  Pyramidal in shape Anterior surface of Brainstem Posterior surface of Brainstem External Features: (Medulla Oblongata) (****Very important –Short note and viva) Features on Anterior surface: (***viva)  Anterior Median fissure-same like spinal cord  Pyramidal dicussation-crossing over of corticospinal tract  Pyramid-an paramedian elevation raised by corticospinal tract  Olive- An oval shaped elevation lateral to pyramid  Inferior Cerebellar peduncle: Bundle of fibres lateral to olive Pyramid VII Vagal triangle Hypoglossal triangle VI Olive Gracile and cuneate tubercles SCP ICP MCP VIII X IX XI XII Pyramidal decussation
  14. 14. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai Features on Posterior surface: (***viva)  Closed Part: lower part with posterior median sulcus, tractus gracilis & cuneatus, Gracile & cuneate tubercles  Open part: Vagal triangle & Hypoglossal triangle Nerves emerging from Medulla oblongata: (***viva)  Abducent nerve (VI cranial nerve): at ponto-medullary junction near pyramid  Facial nerve (VII Cranial nerve) & Vestibulocochlear nerve (VIII Cranial nerve): at pontomedullary junction laterally  Glossopharyngeal (IX cranial nerve) , Vagus (X cranial nerve)and cranial part of Accessory nerve (XI cranial nerve): Behind the olive  Hypoglossal nerve XII Cranial nerve): Between the pyramid & olive Internal Features: Internal features studied by three sections of Pons: 1. Transverse Section (T.S.) at level of Pyramidal decussation 2. Transverse Section (T.S.) at level of Sensory decussation 3. Transverse Section (T.S.) at the level of Open part of Medulla oblongata
  15. 15. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai Transverse Section (T.S.) at level of Pyramidal decussation:  Gray matter seen in the section: 1. Supraspinal nucleus continuation of Substantia gelatinosa (Nucleus for 1st cervical nerve) 2. Spinal Accessory Nucleus (Supply Sternocleidomastoid and trapezius)  White matter seen in the section: 1. Pyramidal Tracts 2. Pyamidal deccussation where 75 % fibres of Pyramidal tract (Corticospinal teract) crosses to opposite side (Motor tract) and form lateral corticospinal tract. (***viva) 3. Other ascending tracts
  16. 16. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai Transverse Section (T.S.) at level of Sensory decussation:  Gray matter seen in the section: (Nuclei at this level) (**viva) 1. Nucleus Gracilis & Cuneatus (Relay station for tectile descriminations, vibration and conscious joint sensation) 2. Nucleus of Spinal Tract of trigeminal nerve (Pain and temperature from face)  White matter seen in the section: 1. Pyramidal Tracts 2. Sensory deccussation where fibres of Gracile & Cuneate tract crosses to opposite side by internal arcuate fibres and forms Medial Lemniscus (Posterior column fibers) (***viva) 3. Lateral and Anterior spinothalamic tract combine to form Spinal Lemniscus 4. Other ascending tracts
  17. 17. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai Transverse Section (T.S.) at level of Open part of Medulla oblongata (At the level of Olive): (****Very important Section)  Gray matter seen in the section: (Nuclei seen at this level) (***viva) 1. Hypoglossal Nucleus (Supply muscles of tongue) 2. Dorsal Vagal Nucleus (Parasympathetic to heart, lung and abdomen) 3. Vestibular nuclei(Balance) & Cochlear Nuclei (Hearing) 4. Inferior Olivary Nucleus (extrapyramidal motor) 5. Nucleus Ambiguus (Combine nucleus of 9th ,10th and Cranial accessory nerve- Pharynx, soft palate Larynx) 6. Nucleus of tractus solitarius (Taste sensation) 7. Nucleus of Spinal Tract of trigeminal nerve
  18. 18. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai 8. Arcuate nuclei: Displaced pontine nuclei  White matter seen in the section: 1. Pyramidal Tracts 2. Medial Lemniscus 3. Tectospinal tract 4. Medial Longitudinal Fasciculus (Paramedian bundle- coordinate activities of different nuclei) 5. Inferior cerebellar peduncle 6. Spinal lemniscus 7. Other ascending tracts Applied Anatomy (Medulla oblongata): Medulla oblongata contain dorsal vagal nucleus which is cardiorespiratory centre and damage to this leads to Death. Hence it is also known as vital center. Arnold-Chiari Malformation is congenital anomaly. 1. Herniation of tonsil of cerebellum and Medulla oblongata through Foramen magnum. 2. Blockage of roof of fourth ventricle. 3. Internal Hydrocephalus. 4. Associated other anomalies like spina bifida.
  19. 19. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai  Lateral Medullary Syndrome: (PICA Syndrome) (**viva)  Blockage of Posterior Inferior Cerebellar Artery  Damage to lateral part of Medulla  Paralysis of palatal and laryngeal muscle  Loss of balance  Vertigo, nausea, vomiting, Nystagmus  Dysphagia-difficulty in swallowing  Dysarthria-difficulty in speech  Loss of pain (Analgesia) and temperature sensations on face  Ipsilateral Horner’s syndrome
  20. 20. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai Medial Medullary Syndrome:  Blockage of Vertebral artery  Damage to Medial part  Contralateral hemiplegia  Ipsilateral Paralysis of muscles of tongue-tip pf tungue deviates to the paralysed side.  Contralateral loss of vibration, joint position and tectile discrimination sensations ==================X================

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