Brain Stem 1. Midbrain 2. Pons 3. Medulla Oblongata 1
Ext. features Medulla Oblongata *Direct continuation of Spinal Cord *Extend from foramen magnum to lower Pons *More than 2.5 cm in length. *Lower part is closed & resemble spinal cord. * Upper part is open & forms part of the floor of 4 th. Ventricle. 2
3
White Matter *(Pyramidal Fibers) Cortico-Spinal Fibers Cortico-Nuclear Fibers *Medial Longitudinal Fasciculus *Spinal tract of Trigeminal Nerve *Post. & Ant. Spino-Cerebellar Tracts *Spinal Lemniscus (Spino-Thalamic Tracts) Med. Lemniscus Fibers *Internal Arcate Fibers Olivo-Cerebellar Fibers Reticulo-Cerebellar Fibers *Descending Tracts (Extra-Pyramidal) 4
Internal structure Main Nuclei: 1. Gracile & Cuneate Nuclei 2. Accessory Cuneate Nuclei 3. Olivary Nuclei (main-pricipal) 4. Accessory olivary Nuclei 5. Arcuate Nuclei 6. Lat. Reticular Nuclei 7. Spinal Nucleus & Tract Trigeminal Nerve 8. Hypoglossal nerve Nuclei 9. Cranial Accessory Nerve Nuclei 10. Vagus Nerve Nuclei 11. Glossopharyngeal Nerve Nuclei 12. Solitory Nucleus & Tract 13. Ambiguus Nucleus 14. Inf. Salivatory nucleus 5
Nuclei of The Medulla Oblongata A. Medullary-Cerebellar Relay Nuclei 1. Olivary nuclei (Main, Principle) 2. Accessory Olivary nuclei 3. Lat. Reticular nucleus 4. Arcuate nucleus 5. Accessory cuneate nucleus B. Crainial Nerve Nuclei 1. Spinal Trigeminal nerve nucleus 2. Hypoglossal nerve nucleus 3. Cranial Accessory nerve nucleus 4. Vagus nerve nuclei 5. Glossophryngeal nerve nuclei C. Other Nuclei 1. Gracilis & Cunate nuclei 6
7
Secondary Reflux Fibs of Trigeminal: To various motor nuclei of cranial nerves (largely uncrossed) Provide connections for many reflexes due to stimulation of areas innervated by V 1.Corneal Reflex (to motor nucl. VII) 2.Lacrimal // (to sup. Salivatory nucl. Of NI) 3.Sneezing // (to RF, N.Ambig, Phrenic N., IC muscles nuclei in spinal cord) 4.Vomitting Reflex (to DMN of X, N.Ambig, Solitary N.) Eff. Fibs. Spinal Nucl. V: 1. Trigemino-thalamic --- (most fibs., cross & join Med. Lemn.) 2.Trigemino-Reticular --- (some fibs.) 3.Trigemino-cerebellar --- (Inf cerebellar ped. (crossed & uncrossed) 4.Trigeminal (for reflexus) --- (Asc. & Dsc. on same side connecting with motor nuclei of cranial nerves, eg. Trigemino- 8 Facial)
Lesions V Nerve Whole Nerve produce: 1- Anesthesia of corresponding Ant. Half of scalp, face, cornea, conjunctiva, mucous membranes (nose, mouth, pre-sulcal tongue) 2- Paralysis & atrophy in muscles supplied by V * Divisions produce: 1- Limited sensory loss & if lingual nerve is affected = loss of taste in Ant. 2/3 of tongue 9
Hypoglossal nuclei (somatic motor) Efferent fibers: To muscles of tongue except Palatoglosses Afferent fibers : *Receive fibers (crossed & uncrossed) & collaterals from reticular neurons (some of these fibs. Constitute the terminal part of a corticobulbar system effecting voluntary movements of tongue * Receive fibers which are 2ndary Glossopharyngeal, Vagal & Trigeminal which mediate reflex tongue movements in response to stimuli from lingual oral, and pharyngeal mucous membrane (ie. Taste, touch, thermal & pain 10
Lesions of Hypoglossal Nerve 1- LMN paralysis of ipsilat. ½ of tongue with loss of move ment, tone & atrophy of muscles affected PN: Since genioglossus effects protrusion of tongue to opposite side, the tongue, when protruded, will deviate to side of injury. 2- The close proximity of the emerging roots of the XII nerve & the pyramidal tracts forms the basis of the Inferior (or Hypoglossal) alternating hemiplegia which results from ventral lessions of this area. = a. LMN paralysis of ipsilateral ½ of the tongue b. A contralateral hemiplegia 11
Desc. Fibs from: MIDLINE 1. Cerebral Cortex (cortico-olivary) 2. Red Nucl. (rubro-olivary) 3. Periaqueductal grey mater Par-olivo-Cerebellar Fibs Dorsal Accessory Olivary Nucl. Olivo-Cerebellar Fibs. Parolivo-Cerebellar Fibs Med. Accessory Olivary Nucl. Principal Olivary Nucl. Asc. Fibs from: Spino-Olivary Tract 12
Vagus Nerve Functional components GSA (general somatic afferents) (cell bodies in superior ganglia of vagus ---relay on Spinal Nucl. Trigeminal N.) GVA (general visceral afferents) ( cell bodies in inferior (Nodose) ganglia of vagus --- relay on dorsal vagal sensory nucl. (Med.Solitary Nucl.)) SVA (special visceral afferents) ( cell bodies in inferior (Nodose) ganglia of vagus --- relay on lat. Solitary nucl.) GVE (general visceral efferents) Cell bodies in: Inf. Salivatory nucl. ---- glands Dorsal vagal motor nucl. --- SVE (special visceral efferents) ( cell bodies smooth in muscle nucl. Ambiguus)
Spinal Nucl. Trigeminal (GSA) Lat. Solitary nucl. (SVA) (Gustatory Nucl.) Med. Solitary Nucl. (GVA) (Dorsal Vagal sensory nucl.) Dorsal Vagal motor nucl. (GVE) Nucleus Ambiguus (SVE) 14
Secondary Fibers X Nerve *From sensory nuclei X & IX go to various motor nuclei of cranial & spinal nerves e.g.: to hypoglossal & salivatory nuclei for lingual & secretory reflexus. * From pharyngeal, respiratory & alimentary mucus membranes pass to nucl. Ambiguus and are involved in pharyngeal & laryngeal reflexes * Other nerve impulses go to dorsal motor nucl. Of X, Phrenic nucl. & nuclei of intercostal muscles in spinal cord which are involved in coughing, vomiting & respiratory reflexes 15
Lesions of X nerve * Bilat. Destruction of X (fatal) (أختناق ) Asphyxia 1- Paralysis of larynx = 2- Paralysis of esophagus & stomach = pain & sever vomiting 3- Loss of vagal reflexes e.g: respiratory reflex = Dyspnea ) صعوبة التنفس )& cardiac acceleration * Unilat. Destruction of X Produces Ipsilat. Paralysis of : Soft palate = Hoarseness ) بحة ) of voice (خدر ) anesthesia, )صعوبة البلع ) Dysphagia Pharynx = Larynx = Dyspnea (therefore ipsilat. Loss of cough & palatal reflexes) * Destruction of visceral motor fibers = ipsilat. Loss of Carotid Sinus reflexes 16
Glossopharyngeal Nerve Functional components GSA (general somatic afferents) (cell bodies in superior ganglia of IX --- relay on Spinal Nucl. Trigeminal N.) GVA (general visceral afferents) (cell bodies in inf. Ganglia (Petrous gang.) of IX--- relay on dorsal vagal sensory nucl.(med.solitary Nucl.)) SVA (special visceral afferents) (cell bodies in inf. Ganglia (Petrous gang.) of IX--- relay on Lat. Solitary Nucl. ) GVE (general visceral efferents) (Inf. Salivatory Nucl.) SVE (special visceral efferents) (Nucl. Ambiguus) 17
Lesions of IX Nerve Major symptoms include: 1- Loss of pharyngeal (gag) rflex 2- Loss of Carotid Sinus reflex 3- Loss of taste in Post. 1/3 rd. Of tongue 18
Nucleus ambiguus (SVE) * Composed of typical LMN whose axons innervate Larynx & Pharynx * Lie ventrally between Hypoglossal & Dorsal vagal nuclei. * Fibers from upper end of this nucl. Travel in Glossopharyngeal nerve (to Stylopharyngeus muscle) * Fibers from lower end travel in Vagus & Cranial accessory nerves * It supply striated muscles of soft palate, Pharynx & Larynx. * Inferiorly it is continues with spinal nucl. of Accessory nerve. Efferents: * To striated muscles of Larynx & pharynx. Afferents: * Terminals from cortico-nuclear tracts (both crossed & uncrossed) for the voluntary control of swallowing & phonation. * Receives impulses from pharyngeal & Laryngeal muscles for tonic control. * Receives impulses from 2ndary. X, XI and V which convey impulses from oral, pharyngeal, & respiratory mucosa that mediate various reflexes (e.g.. Coughing, vomiting, pharyngeal and laryngeal reflexes) 19
Lateral Medullary Syndrome (Of Wallenberg) Symptoms & Signs Damage 1. Dysphagia,Dysarthria Nucl.Ambiguus 2. Ipsilat. Analgesia & Thermoanaesthesia of face Spinal Nucl.&Tract Trigeminal 3.Contralat. Pain & temp. loss of body & neck Spinal lemniscus 4.Ipsilat. Limb & gait ataxia. Inf. Cerebellar peduncle 5.Ipsilat. Horner's syndrome Desc. Sympathetic fibers 6.Vertigo, Nystagmus, Nausea & Vomiting Vestibular Nuclei (Caused by thrombosis of post. Inf. Cerebellar art.) 20
Medial Medullary Syndrome Symptoms & Signs Damage 1.Contralateral Hemiparesis Pyramidal Tracts 2. II impairment of position sense. Med. Lemniscus 3.Ipsilateral paralysis of tongue Hypoglossal Nucl. (with deviation to paralyzed side when protruded) (Caused by thrombosis of medullary branch of Vertebral art.) 21